Category: evolution

More mishigas at Scientific American: A claim that opposition to evolution comes from white supremacy, not religion

July 11, 2021 • 10:00 am

As Scientific American continues its inexorable circling of the drain, it’s approaching the drainhole itself. For, from a week ago, we have an op-ed by Allison Hopper asserting that Americans’ rejection of evolution—73% of Americans are either straight-up Biblical creationists (40%) or think God helped guide evolution (33%)—is due not to religion as many suppose, but to white supremacy. It’s all about racism, Jake! (I was not the first to proposed the religion-is-the-main-cause of rejecting-evolution thesis, but laid out the case, with supporting data, in a paper in Evolution in 2012.)

Hopper rejects that thesis in her Sci Am article, saying that the idea that people reject evolution because of religion is a “lie”. To wit:

“I want to unmask the lie that evolution denial is about religion and recognize that at its core, it is a form of white supremacy that perpetuates segregation and violence against Black bodies. “

Well, she’s dead wrong about her thesis, as I’ll argue below, but also in her claim that evolution denialism “perpetuates segregation and violence against Black bodies.” It does nothing of the sort! You really have to distort your thinking to claim that people are prone to deny evolution because they’re white supremacists, much less embrace the idea that creationism (which is what I’ll call “evolution denial”, since they’re pretty much equivalent in America) creates “violence against Black bodies”. What kind of violence? Has any black person been harmed in the name of creationism? And what is it with this “black bodies” trope?  That seems to me distinctly unwoke, since the trend in “progressive” language is to emphasize the humanity of oppressed people, i.e., “enslaved persons” instead of “slaves”. Saying “black bodies” instead of “black people” clearly dehumanizes people, and I deplore it.

But I digress. Before we examine Hopper’s arguments, such as they are, here are her bona fides from the article:

Allison Hopper is a filmmaker and designer with a master’s degree in educational design from New York University. Early in her career, she worked on PBS documentaries. More recently, she’s been creating content for young people on the topic of evolution. She has presented on evolution at the Big History Conference in Amsterdam and Chautauqua, among other places.

And here’s her article, which you can read for free by clicking on the screenshot below:

Hopper is trying here to jump on the current bandwagon that everything is about race, including rejection of evolution. And, she implies, once we acquaint people with the fact that creationism is a product not of religion but of white supremacy, they’ll give up their creationism and embrace evolution.

Her argument goes like this:

1.) Many people don’t realize that all humans descend from African ancestors (true).

2.) Those African ancestors had dark skin. (Also true.) However, in their case “black” or “brown” does not equate with “oppressed”, since there were no white people to oppress them. Different species of hominin may have oppressed each other, but that had nothing to do with pigmentation.

3.) Importantly, human culture sprang from dark-skinned ancestors who had religion, language, fire, and tool use. These were the foundations, argues Hopper, for the culture we have today. It’s true that these bases (except, perhaps, for religion and language, about whose origin we know virtually nothing) probably sprang from dark-skinned ancestors. But other features of modern culture evolved in Europe and the Middle East, where natural selection had already been lightening skin color. (This constant emphasis on the overweening importance of skin color repels me.) At any rate, agriculture and its attendant amenities of civilization probably arose about 12,000 years ago in the Middle East among people who were not black (but may have been brown) and further developed by people of all colors, including whites and Asians. But who cares? Only someone obsessed with racism and determined to make it the basis for everything bad.

4.) Hopper cares, for she says that evolution’s truth dispels the Biblical story that Adam and Eve (who were supposedly white) were instrumental in creating black people, who descended from a bad person—Cain—who killed his brother. This “mark of Cain” thesis that supposedly connects creationism with white supremacy, is advanced in several ways by Hopper:

Science education in the U.S. is constantly on the defensive against antievolution activists who want biblical stories to be taught as fact. In fact, the first wave of legal fights against evolution was supported by the Klan in the 1920s. Ever since then, entrenched racism and the ban on teaching evolution in the schools have gone hand in hand. In his piece,What We Get Wrong About the Evolution Debate, Adam Shapiro argues that “the history of American controversies over evolution has long been entangled with the history of American educational racism.”

In fact, anybody who looks at the data on creationism sees immediately its connection with the Biblical creation story (not including Cain)—the view that God created everything almost instantaneously, with humans made in His/Her/Their image. Everybody promoting creationism and intelligent design is religious, and all creationist organizations are religious at bottom.

In my life I’ve met hundreds of creationists, and every one of them was religious. (David Berlinski, whom I haven’t met, may be the one exception, but that’s just one person and he may be dissimulating about religion anyway.) They make no bones about their views, either. Yet in none of these people have I heard anything about white supremacy. Sure, there may be racists among creationists—there has to be given the connection between Evangelical Christianity and the South—but you’d have to essentially make things up to argue that creationism comes from white supremacy and that its connection with religion is “a lie.” (At any rate, were Hopper’s story of Cain and Abel true, it still shows a connection between creationism and religion.)

But wait! There’s more:

The fantasy of a continuous line of white descendants segregates white heritage from Black bodies. In the real world, this mythology translates into lethal effects on people who are Black. Fundamentalist interpretations of the Bible are part of the “fake news” epidemic that feeds the racial divide in our country.

There are those “Black bodies” again.  But what are the “lethal” effects? Were black bodies really killed because white bigots and lynchers were motivated by a refusal to accept our ancient ancestry? I doubt it, and I doubt whether they were motivated by religion, either. They were motivated, I believe, by tribalism and the heritage of slavery with its attendant beliefs that blacks were inferior beings.

In fact, when Hopper talks about the dearth of children’s books on evolution, she inadvertently admits that religion (not the story of Cain and Abel!) is tilting kids towards creationism:

If you go on Amazon and look up “children’s books on evolution” you will find about 10–15 relevant titles. This is in contrast to the hundreds of children’s books on other scientific subjects such as chemistry, astronomy and other less controversial subjects. I found only one book on evolution for preschoolers, called Grandmother Fish. The author had to self-fund the book through Kickstarter.

On the other hand, there are hundreds of children’s books available on Amazon that focus on biblical origin stories. Science deniers are pumping money into a well-funded antievolution machine. In 2007, the creationists built their own Bible-themed museum and amusement park. What they understand is that to reach young children you need music, colorful characters and celebration.

Kids get their religion long before they learn evolution, and by the time they’re presented with Darwin and his successors, they’ve had at least a decade of indoctrination in the Bible, with many being Biblical literalists. They are effectively immunized against evolution. Racism is a separate issue.

In the end, Hopper argues that if we can just tell the story of evolution properly, including that we all came from Africa and our earliest ancestors were dark-skinned, creationism would go away:

. . . even in the current literature about human origins that we do have, the end point of evolution is often depicted as a white man carrying a spear. This image not only eliminates our African heritage but also erases women and children from the picture. Because evolution is foundational knowledge, we need the story to be told in many different ways, by many different voices.

As we move forward to undo systemic racism in every aspect of business, society, academia and life, let’s be sure to do so in science education as well. Embracing humanity’s dark-skinned ancestors with love and respect is key to changing our relationship to the past, and to creating racial equity in the present. These ancient people made the rest of us possible. Opening our hearts to them and embracing them as heroic, fully human and worthy of our respect is part of the process of healing from our racist history.

I wasn’t aware that the teaching of evolution was systemically racist; do teachers really deny that our ancestors were African? And does Hopper really believe that accepting that will get rid of racism? Really? Even Darwin was a monogenist, saying that all groups of humans arose from a single ancestor who probably lived in Africa. Did that get rid of racism? I don’t think so, though some people think Darwin’s monogenism was part of a strategy to combat racism.

(I can’t get over my gag reflex when hearing that we need to embrace our ancestors with “love and respect”, since I don’t know that they were either lovable or respectable)

Okay, now what’s the evidence against Hopper’s thesis? It’s strong:

a.) Ask people why they think evolution didn’t happen. Many will say because they believe the Bible or the Qur’an. Nobody will say because it shows that white people are superior. (Of course, you can say they won’t admit their bigotry.)

b.) Every creationist organization from Answers in Genesis to the Discovery Institute is based on religion, while we find no creationist organizations whose platform is white supremacy. As I said, the two are tangentially connected because of the religious and white-supremacist nature of the American South, but this is a matter of correlation, not causation.

c.) Most telling: several surveys, listed and summarized in this paper, show that blacks and Hispanics deny evolution more than do whites. This is the opposite of what Hopper predicts, but makes sense under the “religion-first” hypothesis, since blacks and Hispanics tend to be more religious than whites in general.

d.) There is a highly statistically significant negative correlation between the religiosity of 34 European countries and their acceptance of evolution, as I noted in my Evolution paper. Most of these countries are nearly all white, save France and Germany, which have high acceptance of evolution (and more black people than, say, Iceland or Demark). The US is near the bottom in accepting evolution (I’ll give the data in a minute), not because the U.S. has a higher percentage of whites than most European countries—it doesn’t—but because the U.S. is far more religious then Europe.

Here’s the correlation I found. The U.S., labeled, is next to last in accepting evolution, while below us lies only Turkey: a Muslim country that, by the way, happens to comprise many “people of color”. Note that the most religious countries, to the right, are the least accepting of evolution. I discuss issues with these data (nonindependence, etc.) in the Evolution paper.

And here are the data from Miller and Scott (2006) that I used to make the plot for my own paper:

The religiosity of these countries, which appears in the graph above, came from other sources given in my Evolution paper.

The thing to note is that virtually all these countries are white, and yet the correlation holds across them all. As I said, the countries with the highest proportion of evolution rejectors (those at the bottom)—are not only the most religious, but also probably contain the highest proportion of people of color. This is what the religious hypothesis proposes, but it goes counter to Hopper’s thesis, which predicts that the whitest countries should be the least accepting of evolution, for rejection of evolution is a sign of white supremacy. (Of course, you could argue that white supremacy will be manifested only in countries with a substantial proportion of black people, but that’s pushing it.) In fact, Hopper’s argument is a post facto confection to support anti-racism, and appears to make no predictions that seem to stand up to scrutiny.

It seems to me that Hopper is not only deeply misguided, but also motivated by ideology, tying creationism directly to white supremacy, and almost completely dismissing its connection to religion. As I always say, “You can have religion without creationism, but you can’t have creationism without religion.” Hopper seems to have deliberately ignored data inimical to her hypothesis, which of course is what one does when afflicted with the kind of confirmation bias that comes with wokeness.

And it’s just another sign that whoever’s in charge of Scientific American is letting through ill-informed and erroneous material.  What has happened to that once-respectable magazine? Is there no longer an audience for the lively yet informative articles they used to publish? Are they becoming the Evergreen State of popular science magazines?

h/t: Eli

A discussion on genetics, evolution, and information with Richard Dawkins

June 30, 2021 • 10:30 am

Reader Luke sent a recently filmed 48-minute discussion between Richard Dawkins and Jon Perry. Luke says “Perry does the excellent Stated Clearly YouTube channel. This was posted on his ‘personal’ site.”

Luke added this, too:
It’s a good conversation. It mostly focuses on River Out Of Eden and the ideas within that book. I know Richard has a new book out, but it’s refreshing here that he takes a deep dive into his past writings. While he touches upon atheist arguments, most of the conversation concerns Darwin, evolution, the genetic code, information theory, computers and function. This, I think, is where Dawkins is at his finest — talking about evolution. There’s a great moment when Dawkins is talking about the genetic code and machine code and Perry pulls out a strip of computer tape! [JAC: this happens at 12:48.] A great illustration of the ideas discussed!
It’s clear Perry is very much inspired by Dawkins, and it’s good to see. His YouTube channel is one of the best and most consistent.

Because of my past as a working biologist, I found the discussion of biology (sexual selection, brood parasitism, etc.) more interesting than the long discussion of code, the genetic code, information, and so on.

I enjoyed the section about whether animal signals evolve via genes that improve “cooperation.”  Whether you answer this “yes” or “no” depends on how you conceive of “cooperation”.  If you mean that cooperative signals evolve even though they reduce the fitness of the replicators within populations (i.e. cooperation as pure altruism), there’s no way that cooperation can evolve by individual selection (more accurately, by differential replication of genes among individuals in a population). Remember, you have to include kin and reciprocity when dealing with the evolution of cooperation within a population.

Most biologists think that the vast bulk of cooperation in animals evolves in a way that increases the fitness of the cooperators in a population. It confers an individual advantage to cooperate. You scratch my back and I’ll scratch yours, ergo you give excess food to your fellows so long as they remember to give excess food to you when you need it. Lions in a pride can gain advantages by cooperating in a hunt by being able to get more per capita food by being able to bring down larger prey or by being more successful at catching prey.

If you want a general increase in cooperation that does not enhance the fitness of individuals, you’ll have to posit forms of group selection.

I know of no examples of cooperation in animals—including any evolved cooperation in primates like ourselves—that cannot be seen as having evolved by individual (or genic) selection. Such examples, to be convincing, would have to show that while they may increase the longevity or “splittability” of a group, would have to reduce the fitness of the cooperators themselves, even when you include their kin. Some aspects of social insect behavior might conform to a group selection model, but recent work refuting such suggestions by Martin Nowak and his colleagues suggests this isn’t the case. At this point we can say that evolutionists know of know adaptations in organisms that must have evolved by group rather than “individual” selection. In the last chapter of my book on Speciation with Allen Orr, however, we describe how some evolutionary trends might be due to a form of group selection, but these are not features or behaviors of individuals.

Our letter to Science about Agustín Fuentes’s Darwin-bashing

June 21, 2021 • 1:30 pm

On May 21, Princeton anthropologist Agustín Fuentes published a takedown of Darwin in a Science op-ed on the 150th anniversary of Darwin’s The Descent of Man and Selection in Relation to Sex. Asserting that Darwin was a racist, a white supremacist, and a man whose ideas justified “colonialism” as well as “genocide,” Fuentes’s piece was over the top: a typical and execrable specimen of holding someone living decades ago responsible for adhering to the moral norms of his time. (Actually, Darwin, an abolitionist, was a far sight better than many of his contemporaries.) In other words, according to Fuentes, Darwin should have known better. But I bet you ten to one that Fuentes, had he been Darwin’s contemporary, would have been even more of a moral reprobate than Charles himself.

I criticized Fuentes’s piece here (and Robert Wright did elsewhere), though Jonathan Marks, a well known anthropological firebrand, sprang to Fuentes’s defense. Several weeks ago, a bunch of us evolutionary biologists got together and wrote a joint letter to Science criticizing Fuentes’s piece.  The journal sat on it, said it wouldn’t appear in print, but have at last put it online. You can see the link to our letter below, but I’ve posted the whole thing, along with our names, addresses, and the references we use.

Click on the screenshot to see our letter (and Marks’s):

What we wrote:

RE: “The Descent of Man”, 150 years on
(6 June 2021)

“The Descent of Man” 150 years on

In this 150th anniversary year of Darwin’s “The Descent of Man” (1), Science published one article celebrating the progress in human evolutionary science built on Darwin’s foundations (2), along with a second, Editorial article, three quarters of which instead pilloried Darwin for his “racist and sexist view of humanity” (3). Fuentes argues that students should be “taught Darwin as [a] man with injurious and unfounded prejudices that warped his view of data and experience”. We fear that Fuentes’ vituperative exposition will encourage a spectrum of anti-evolution voices and damage prospects for an expanded, more gender and ethnically diverse new generation of evolutionary scientists.

What Darwin wrote was of course shaped by Victorian realities and perspectives on sex and racial differences, some still extant today, but this is not a new revelation [4]. Rather than calmly noting these influences, Fuentes repeatedly puts Darwin in the dock for the Victorian sexist and racist norms within which he presented his explosive thesis that humanity evolved. Fuentes incorrectly suggests that Darwin justified genocide. Darwin was frequently and notably more modern in his thinking than most Victorians. In The Descent he demolished the slavery-justifying view of different races as separate species, so inspiring the anti-racist perspectives of later anthropologists like Boaz (5). On sexism, Darwin suggested that education of “reason and imagination” would erase mental sex differences (1, p. 329). His theory of sexual selection gave female animals a central role in mate choice and evolution (1).

Students taught about the historical context for Darwin’s writing should appreciate how revolutionary Darwin’s ideas were, challenging many (but not all) prevailing Victorian perspectives (6). We lament the failure to celebrate the vast impact of those ideas at the expense of the distorting treatment Fuentes offers.

Andrew Whiten1, Walter Bodmer2, Brian Charlesworth3, Deborah Charlesworth3, Jerry Coyne4, Frans de Waal5, Sergey Gavrilets6, Debra Lieberman7, Ruth Mace8, Andrea Bamberg Migliano9, Boguslaw Pawlowski10 and Peter Richerson1

1School of Psychology and Neuroscience, University of St Andrews, St Andrews, KY16 9PE, UK. 2Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK. 3School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK, 4Department of Ecology and Evolution, University of Chicago, 1101 E. 57th St., Chicago, IL60637, USA. 5Psychology Department (PAIS Bldg), Suite 270, 36 Eagle Row, Emory University, Atlanta, GA 30322, USA. 6Department of Ecology and Evolutionary Biology, Univ of Tennessee Knoxville, TN 37922, USA. 7Department of Psychology, University of Miami, Coral Gables, FL 33146, USA. 8(Editor in Chief, Evolutionary Human Science) Department of Anthropology, University College London, London, UK. 9Department of Anthropology, University of Zurich, 190 Winterthurerstrasse, Zurich 8057, Switzerland. 10(President, European Human Behaviour and Evolution Association) Department of Human Biology, University of Wroclaw, ul. S. Przybyszewskiego 63, 51-148 Wrocław, Poland. 11Department of Environmental Science and Policy, University of California, Davis, CA 95616, USA.
Corresponding author. Email: a.whiten@st-andrews.ac.uk

REFERENCES
1. C. Darwin. The Descent of Man and Selection in Relation to Sex. With an introduction by J. T. Bonner and R. M. May. (Princeton University Press, Princeton, 1871/1981).
2. P. J. Richerson, S. Gavrilets, F. B. M. de Waal. Modern theories of human evolution foreshadowed by Darwin’s the Descent of Man. Science 372, 806.
3. A. Fuentes. “The Descent of Man” 150 years on. Science 372, 769.
4. A. J. Desmond, J. R. Moore. Darwin. (Penguin, London, 1992).
5. P. J. Richerson, R. Hames. Busting myths about evolutionary anthropology. Anthropology News, July 18 (2017) doi: 10.1111/AN.510
6. H. E. Gruber. Darwin on Man. (Princeton University Press, Princeton, 1974).

We could have said a lot more, but there is a strict word limit for Science letters.

Punctuated equilibrium is dead; long live the Modern Synthesis

June 13, 2021 • 9:30 am

“If [Ernst] Mayr’s characterization of the synthetic theory [of evolution] is accurate, then that theory, as a general proposition, is effectively dead, despite its persistence as textbook orthodoxy”.—Gould, 1980

“If Steve Gould’s characterization of punctuated equilibrium involves the evolutionary mechanisms that he and Niles Eldredge proposed, then that theory, as a general proposition, is effectively dead, despite its persistence in Gould’s writings.”—Coyne, this post

Punctuated equilibrium (PE) was first proposed in a paper by Niles Eldredge and Steve Gould (“E&G”; reference below) in 1972, the year before I entered graduate school. When I entered Harvard in 1973  it was a huge deal, heavily promoted by Gould, a professor in the Museum of Comparative Zoology, as a replacement for the view of evolution most people held (“neo-Darwinism).  Not a little of the theory’s popularity came from Gould’s nonstop promotion of it as well as his extraordinary ability to write popular science.

At first the theory was largely about the pace of evolution. Instead of imperceptibly gradual change in a species over time (the view Darwin proposed, though Darwin did note in the Origin that evolution could also be rapid), Eldredge and Gould proposed that the pace of evolution was jerky, with big changes occurring relatively rapidly over evolutionary time little evolution happening the rest of the time. (This of course concerned only morphology, and was tested largely using hard parts—the parts most often preserved in fossils.)

Most of us microevolutionists were willing to go with the data, and some fossil data did seem to show an episodic pattern of morphological change. But of course there was argument about this, for what constitutes “big” versus “small” change in fossils? Further, the fossil record is often incomplete, so missing strata can make a gradual change look like a near-instantaneous big change.

Nevertheless, the theory that the pace of evolution could vary widely sat comfortably within the neo-Darwinian paradigm, which predicts that change will be rapid when natural selection is strong, and small when selection is weak or nonexistent. I remain open about the prevalence of the pattern, for I don’t know all the data.

But, over time, PE became more than a hypothesis about the relative rate of evolutionary change in fossil lineages. It morphed into a theory of evolutionary process—a theory that was pretty much “non-neo-Darwinian” and also much more controversial. And while the pattern may be right, the processes proposed by E&G are so wrong that I’d call them “definitively falsified”.

Over time, the following six assertions became part of Gould and Eldredge’s theory, and were proposed by the pair themselves:

a.) The claimed observation that most of the times species in the fossil record didn’t change (i.e., exhibited “stasis”) was not due to weak selection or an absence of selection, nor was it due to “stabilizing selection”: the kind of selection in which the average character in a population is the most fit, and extremes are selected against. That is the classic explanation for a lack of evolutionary change over time. These explanation were rejected by E&G in favor of two other explanations:

1.) Organisms have “developmental constraints”: there may be selection, say, to make individuals of a species bigger, but the species doesn’t get bigger because it either lacked genetic variation for bigger size or, alternatively, attaining a bigger size would have negative effects on the average fitness of the species (for example, if food is scarce, getting bigger might lead to faster starvation).

2.) Gene flow among populations of a species means that no population could change in response to local selection pressures because there was a constant influx of genes from other populations that didn’t experience such selection. This constant mixing of genes from populations undergoing different forms of selection averaged out to no net change in the appearance of a fossil species.

b.) Punctuated change in morphology can occur only when the genome is somehow “shaken up”, and this shake-up occurs during speciation events—when one lineage branches into two or more lineages. Absent such splitting events, a species stays static.

c.) The genomic discombobulation that somehow releases a species from its stasis—that is, loosens the developmental constraints—occurs when, as supposedly happens during most speciation events—a small peripheral population undergoes a form of “genetic revolution”, a kind of speciation in which reproductive barriers arise during an interaction between natural selection and genetic drift (random changes in the proportion of gene variants that are most prevalent in small populations.) At the time of this theory, several evolutionists, including Sewall Wright and Hampton Carson, had proposed that some types of evolutionary change require genetic drift in small populations. Without those population “bottlenecks”, these proponents said, species don’t change much. E&G drew on these ideas to buttress the episodic nature of evolution. One problem here is that there was and is little evidence that this kind of drift-associated change occurs, and almost no evidence that it’s ever associated with the appearance of a new species. Evolutionists have repeatedly put species through extreme bottlenecks—as few as two individuals—and have never seen that lead to even the beginning of reproductive isolation. (Reproductive isolation is the sine qua non of speciation to evolutionists.)

d). These claims all combine in the following way to lead to a punctuated evolutionary pattern. A big, widespread species is resistant to evolutionary change for the reasons mentioned above. Then, a small peripheral isolate population, cut off from the rest of the species, forms. Being small, it undergoes genetic drift, which releases the evolutionary constraints and allows the isolate to undergo rapid and substantial evolution.  Eventually, the isolate rejoins the main population, but by that time it’s evolved reproductive isolation from the other populations and is thus a new species. For reasons unexplained, the isolate quickly replaces the other populations. And voilà!—one sees a big change in the fossil record as the small and changed population supplants its ancestral species.

e.) But there’s another way that big morphological change can occur rapidly, too—one that was promoted by Gould: macromutation. This is the notion that changes in an animal’s appearance, behavior, physiology, and so on, don’t need to occur in small, incremental steps (the “Darwinian” pattern) but can occur via mutations that make big jumps, creating “hopeful monsters” (“saltations”). This idea was popularized by Richard Goldschmidt in the 1930s, and was revived by Gould in PE. Gould, for example, said this in a 1982 paper in Science.

 I envisage a potential saltational origin for the essential features of key adaptations. Why may we not imagine that gill arch bones of an ancestral agnathan moved forward in one step to surround the mouth and form proto-jaws? (Gould, 1980)

When called out for the absence of adaptations based on such huge mutations, Eldredge and Gould backtracked, claiming that PE was “never meant as a saltational theory”.  As you see, and this is true of other parts of PE, Gould in particular waffled about what the mechanisms of episodic fossil change really were.

f.) One of the most important parts of PE, worked out largely by Gould, was the claim that major features of adaptive evolution, and evolutionary trends in general, like the increase in body size in many lineages (“Cope’s Rule”) was due to species selection. This is a process of differential speciation and extinction that is said to occur not within species (that’s just classical Darwinism), but among species.  A further claim was that the changes within species had little to do with selection itself (they may have resulted from drift)—or at least little to do with the process of differential speciation and extinction.

So, for example, an increase in body size among a group of mammals over time would be explained by species selection this way: each species attains its average body size either by drift or by forms of selection that have no relationship with the persistence, speciation rate, or extinction of species. But it may happen that, for other reasons, the biggest species either speciate faster or go extinct more slowly. Over time, then, we’d see a pattern among lineages of an increase in body size, but this has nothing to do with classical Darwinian selection on gene forms.

The problem with this is that species selection cannot account for complex adaptations like jaws so easily. Each feature of an adaptation would have to evolve by a process of differential extinction or speciation, and evolving a complex adaptation would take a gazillion years.  That’s because species selection is much slower than individual Darwinian selection since the former relies on replacement of species over evolutionary time, while the latter relies on the rapid replacement of gene forms within a species, which can occur over a few thousand generations or fewer. Further, the evidence for species selection as a general explanation of evolutionary trends is very thin. In his last big book, The Structure of Evolutionary Theory, a 1400-page, poorly written monster that I actually read (and wish I hadn’t), Gould winds up admitting that he can’t adduce a single good example of species selection. However, in the last chapter of my book with Allen Orr, Speciation, we do make a case that a limited form of species selection may operate in nature and can explain evolutionary trends but not adaptations themselves. Species selection is just not as ubiquitous as Gould thought.

******

So apart from a) and the presence of genetic drift, virtually every part of PE is “non-neo-Darwinian”: processes that aren’t considered widely as part of the modern evolutionary synthesis. That doesn’t mean that they’re wrong, but when examined closely, the evidence for these ancillary assertions is virtually nonexistent. Although to G&E, PE represented a Kuhnian “paradigm shift”, closer examination shows that these components (peak shifts, connection of morphological change with speciation, restriction of response to selection by developmental constraints, saltation, widespread species selection etc., etc.) are individually not common, and in tandem seem impossible to form the basis of a convincing theory. Despite that, Gould claimed that PE put neo-Darwinism to rest (see his quote at the top of the article).

Now I could write in detail why the assertions above are dubious, and why PE as a mechanism of evolutionary change is almost certainly wrong, bu that case has already been made. It was first made by three of my colleagues, Brian Charlesworth, Russ Lande, and Monty Slatkin, in a 1982 paper in Evolution that pretty much put the mechanism of PE to rest. You can read that paper below; it’s a classic not of modern evolutionary genetics, and also a paradigm of close examination and debunking of a popular theory (click on screenshot for the pdf). The debunking involved a massive mustering of evidence from genetics, population-genetic theory, laboratory experiments, field experiments, artificial selection, and geology. The last bit of their conclusions says this:

We have also demonstrated, as has Orzack (1981), that punctuationists have often severely distorted the neo-Darwinian theory of evolution. Punctuationists are mainly criticizing oversimplified versions of neo-Darwinism (which are currently popular in some fields) rather than the original statements of this theory and the evidence which has been used to support it. Furthermore, some of the genetic mechanisms that have been proposed to explain the abrupt appearance and prolonged stasis of many fossil species are conspicuously lacking in empirical support. Thus, we do not feel logically compelled to abandon neo-Darwinism in favor of the theory of punctuated equilibria.

This paper of Charlesworth et al. was expanded and brought up to date by the new “Perspectives” paper of Hancock et al. in Evolution (reference below, pdf here).


And here is the abstract, supporting the conclusions of Charlesworth et al. (my emphasis)

The Modern Synthesis (or “Neo-Darwinism”), which arose out of the reconciliation of Darwin’s theory of natural selection and Mendel’s research on genetics, remains the foundation of evolutionary theory. However, since its inception, it has been a lightning rod for criticism, which has ranged from minor quibbles to complete dismissal. Among the most famous of the critics was Stephen Jay Gould, who, in 1980, proclaimed that the Modern Synthesis was “effectively dead.” Gould and others claimed that the action of natural selection on random mutations was insufficient on its own to explain patterns of macroevolutionary diversity and divergence, and that new processes were required to explain findings from the fossil record. In 1982, Charlesworth, Lande, and Slatkin published a response to this critique in Evolution, in which they argued that Neo-Darwinism was indeed sufficient to explain macroevolutionary patterns. In this Perspective for the 75th Anniversary of the Society for the Study of Evolution, we review Charlesworth et al. in its historical context and provide modern support for their arguments. We emphasize the importance of microevolutionary processes in the study of macroevolutionary patterns. Ultimately, we conclude that punctuated equilibrium did not represent a major revolution in evolutionary biology – although debate on this point stimulated significant research and furthered the field – and that Neo-Darwinism is alive and well.

So the best you can say about the mechanism of PE, a claim I’ve heard many times, was that it furthered the field of paleobiology—brought paleontology to the “high table of evolutionary biology”, as someone asserted. Well, while it did stimulate debate about the relative frequency of rapid versus gradual change in the fossil record, the falsity of its claims about mechanism was already known to evolutionary geneticists when PE was first proposed! Charleworth et al. simply collected all the theoretical and empirical work that showed the falsity of the mechanism.

I remember debating this issue with Steve Gould in our conference room at Harvard, asking him to explain the details of PE’s mechanism. Gould got more and more exercised, and wound up tarring me by telling me that I was just a “hidebound gradualist.”  I still wear that label with pride.

Later, Brian Charlesworth and I had several exchanges criticizing PE in the journal Science (see Coyne and Charlesworth references below).

It apparently wasn’t enough for E&G to point out a pattern in the fossil record that might have been real (I still don’t know how ubiquitous “jerky” evolution is). No, they wanted to go further—to be Kuhnians and tear down the wall of evolutionary theory, erecting the new paradigm of PE in its place. Well, such an endeavor is fine, but the new paradigm hasn’t worn well, and in fact was stillborn when first proposed.

I’m not sure whether paleobiologists still teach punctuated equilibrium as a viable theory, but if you hear that claim, remember this: PE as a pattern in the fossil record may well be correct, but as a mechanism of evolutionary change is “not even wrong.”

Addendum: I don’t want to go through the Charlesworth et al. and Hancock et al. papers in detail, as you can read them for yourselves. But if you have specific questions about the mechanism of PE that I can answer briefly, put them in the comments.

Stephen Jay Gould (left) and Niles Eldredge (right) flanking their mentor, Norman D. Newell (seated) on the occasion of Dr. Newell’s 90th birthday celebration at the American Museum of Natural History in New York in February, 1999. Photo by Gillian Newell. Source.

______________

Charlesworth, B., R. Lande, and M. Slatkin. 1982 A Neo-Darwinian commentary on macroevolution. Evolution 36: 474– 498.

Coyne, J. A. and B. Charlesworth.  1996.  Mechanisms of punctuated evolution (technical comment). Science 274:1748-1749. (includes response by Elena et al.)

Coyne, J. A. and B. Charlesworth. 1997.  Punctuated equilibria (technical comment).  Science 276:338-340.

Eldredge, N. and S. J. Gould. 1972. Punctuated equilibria:  An alternative to phyletic gradualism. Pp. 82-115 in T. J. M. Schopf, ed. Models in Paleobiology. Freeman, Cooper, San Francisco.

Gould, S. J. 1980. Is a new and general theory of evolution emerging?. Paleobiology 6 119-130.

Hancock, Z.B., Lehmberg, E.S. and Bradburd, G.S. (2021), Neo-darwinism still haunts evolutionary theory: A modern perspective on Charlesworth, Lande, and Slatkin (1982). Evolution. https://doi.org/10.1111/evo.14268

Response by Brian Charlesworth to the latest episode of Darwin-dissing

June 9, 2021 • 9:30 am

My friend, colleague, and former chair Brian Charlesworth, a well known evolutionary geneticist, had some thoughts about Agustín Fuentes’s op-ed critique of Charles Darwin recently published in Science. (See my own posts about Fuentes here, here, and here.)  As you’ll see, he feels that Fuentes distorted Darwin’s views; Brian attempts a longer and more objective summary.

Fuentes’s thesis was not just that Darwin himself was, on the subject of human evolution, often sexist, racist, and bigoted, but that his views were injurious, justifying “empire and colonialism” as well as “genocide” to those who adopted the thesis of “survival of the fittest.” As I’ve argued before, Fuentes grossly exaggerates Darwin’s bigotry, for although the man shared some of the prejudices of his time, he was far more liberal than the average English gentleman. (For one thing, Darwin was an ardent abolitionist.) Also, Darwin is not responsible, and in fact rejected, the “social darwinism” that justified oppression and conflict by saying it was “natural”.

Brian’s collection of thoughts on Fuentes’s piece is below.  Statements by Darwin himself are indented in normal type, while Fuentes’s statements are indented and italicized.  But first, here’s Brian’s explanation of why he put together the notes; I’ve added a photo of Brian to the bottom of this post.

Why did I compile these notes on Agustín Fuentes’ Science editorial on The Descent of Man, where he accused Charles Darwin of justifying genocide on the basis of the ‘survival of the fittest’? I had previously been a co-author of a paper (Bodmer, W.F. et al. 2021 Heredity ; https://doi.org/10.1038/s41437-020-00394-6) that described the views on eugenics and race of the great statistician and geneticist, R.A. Fisher. This prompted a good deal of criticism, including attempts by an anti-racist group at the University of Edinburgh to have the paper suppressed, on the grounds that it was a “defence of the geneticist R.A. Fisher’s abhorrent views on race and eugenics” (https://twitter.com/UoEREN/status/1374408913861308431). This attracted the attention of the UK national press, with the Daily Mail newspaper asserting that Fisher advocated “sterilisation of people from races he considered ‘mentally inferior’ ” (University of Edinburgh in free speech row over article praising scientist who advocated eugenics | Daily Mail Online).

Both this episode and the Fuentes article raise two issues. First, while I strongly support removing social and racial injustices, I feel that it is important that we examine the context of opinions expressed in past times, and arrive at a judgement of how positive achievements can be recognised, even when some beliefs are expressed that are obnoxious to people today. Conducting such an examination should not be viewed as defending views that are today regarded as abhorrent, as happened to the paper about Fisher. Enormous benefits have accrued to humanity from Fisher’s statistical innovations and from Darwin’s biological discoveries. This contrasts with slave traders, slave owners, segregationists and Nazis, who did nothing but harm. Second, we must get the facts right. Darwin never justified genocide (indeed, he had a lifelong hatred of cruelty in any form); Fisher never referred to ‘inferior races’ or advocated their sterilization.

My notes on the Fuentes article represent an attempt to give a clearer picture of what Darwin actually wrote and thought than was conveyed by the article itself.

****************************************************************************

Some Notes on A. Fuentes’ Science Editorial about Darwin’s The Descent of Man

(Science 2021, 372: 769 DOI: 10.1126/science.abj4606)

Brian Charlesworth, Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh

First, it should be recognized that modern readers of the Descent will find a number of statements and wordings objectionable, notably the use of the terms “lower races” and “savages”. This was, however regrettable, the language commonly used by Victorian writers. It does not shed a flattering light on the prejudices of that age, but it should be recognized that Darwin’s general views on social issues, such as his hatred of slavery and child labour, were among the most enlightened of his time. For example, he was a member of the 1864 committee that urged the prosecution of Governor Eyre of Jamaica for his brutal suppression of protests by the black population.

This aspect of Darwin is barely acknowledged by Fuentes, who remarks that:

“Descent” is often problematic, prejudiced, and injurious. Darwin thought he was relying on data, objectivity, and scientific thinking in describing human evolutionary outcomes. But for much of the book, he was not. “Descent,” like so many of the scientific tomes of Darwin’s day, offers a racist and sexist view of humanity.

This gives a distorted view of the book as a whole. Including Selection in Relation to Sex, there are 954 text pages in the 1874 second edition (John Murray version; the pagination varies among versions), and pp. 319-845 are devoted to animals, not humans. On my reading, the other 45% of the book includes seven passages that express what appear to be racist and sexist views. The most obnoxious of these (p.213) was not written by Darwin himself, but is a lengthy quotation from a Mr Greg concerning competition between Saxons and Celts (the latter being held to be inferior).

[From Fuentes’s piece]:

Darwin portrayed Indigenous peoples of the Americas and Australia as less than Europeans in capacity and behavior. Peoples of the African continent were consistently referred to as cognitively depauperate, less capable, and of a lower rank than other races.

There is only a handful of references to the mental abilities of Africans in the book; contrary to the impression given by Fuentes. Darwin’s statements about mental differences between the races are ambiguous and fluctuating, and many of them are very enlightened compared with remarks by his contemporaries such as T.H. Huxley, Karl Marx and Walt Whitman. For example, on p.276 he says:

“ .. they [races] are found to resemble each other closely in a multitude of points. Many of these are of so unimportant or of so singular a nature that it is extremely improbable that they should have independently acquired by aboriginally distinct species or races. The American aborigines, Negroes and Europeans are as different from each other in mind as any three races that can be named, yet I was incessantly struck while living with the Fuegians on board the “Beagle”, with the many little traits of character, shewing how similar their minds were to ours; and so it was with a full-blooded negro with whom I happened once to be intimate.”

Furthermore, in Darwin’s diary of the voyage of the Beagle (July 3, 1832), he describes the black men of Brazil in complimentary terms:

“I cannot help believing they will ultimately be the rulers. I judge of it from their numbers, from their fine athletic figures … & from clearly seeing their intellects have been much underrated; they are the efficient workmen in all necessary trades.”

It should be remembered that Darwin (and his contemporaries) had no clear grasp of the distinction between genotype and phenotype that is at the core of modern genetics, and he attached considerable significance to the inheritance of acquired characters in the Descent. Therefore, when he referred to race or sex differences in mental traits, it is often unclear whether he thought they were purely cultural in origin, or were innate; but several passages make it clear that Darwin attached considerable importance to cultural factors. When comparing the indigenous inhabitants of New Zealand and Tahiti, he remarked on the effects of education by missionaries on “teaching them the arts of civilization” on the former and the “kind, simple manners” of the latter (Letter to Caroline Darwin, 27 December 1835).

At the end of Chapter 7, Darwin argued forcefully that civilized societies have comparatively recently emerged from barbarian societies and (p.223) noted that:

“The Tahitians when first visited had advanced in many respects beyond the inhabitants of most of the other Polynesian islands. There are no just grounds for the belief that the high culture of the native Peruvians and Mexicans was derived from abroad.”

Fuentes goes on to say:

These assertions are confounding because in “Descent” Darwin offered refutation of natural selection as the process differentiating races, noting that traits used to characterize them appeared nonfunctional relative to capacity for success. As a scientist this should have given him pause, yet he still, baselessly, asserted evolutionary differences between races.

Darwin appealed to sexual selection as a process in differentiating human populations; this is simply a sub-class of natural selection as far as evolutionary mechanisms are concerned.

Fuentes’s statement seems to suggest that he thinks that there are no genetic differences between human populations and that natural selection has nothing to do with them. This is in contradiction with many findings of human population geneticists concerning the action of selection on important traits, such as resistance to malaria, the ability to resist anoxia in high altitude populations, and lactose tolerance in populations that consume milk products. Even without selection, genetic differences between populations in selectively neutral characters can evolve by random genetic drift – subtle differences in the frequencies of large numbers of DNA sequence variants have been revealed even within the population of the British Isles.

Accepting the evidence for genetic differences between human populations carries no implication of believing in racial purity or superiority, or the related pseudo-scientific justifications for discrimination with which we are all too familiar. For quantitatively varying traits, which are subject to both environmental and genetic influences, differences between populations are statistical, in the sense that there is much variability within populations (as Darwin himself noted in relation to human races), which is often greater than any between-population variation. Without complete standardisation of the environment, it is impossible to determine whether observed differences in the mean values of a trait between populations has a genetic basis (this is the basis for the classic “common garden” experiments of plant evolutionary geneticists).

He went beyond simple racial rankings, offering justification of empire and colonialism, and genocide, through “survival of the fittest.” 

There is no evidence Darwin use his science to justify “empire and colonialism, and genocide”. It is true that, like most Victorians, he took a favourable view of British colonization of the Americas, Australia and New Zealand, as shown by some of his statements. But his discussion of the extinction of indigenous populations in Chapter 7 of the Descent emphasised the role of disease and demoralisation, and it is unjust to suggest that he thought that such extinctions were to be applauded.

For example, in his Beagle Diary (4th-7th of September 1833), he exclaims with horror about the massacres of Indians in Patagonia:

“Who would believe in this age in a Christian, civilised country that such atrocities were committed?  … The country will be in the hands of white Gaucho savages instead of copper coloured Indians. The former being little superior in civilisation, as they are inferior in every moral virtue”.

Fuentes also says:

In “Descent,” Darwin identified women as less capable than (White) men, often akin to the “lower races.” He described man as more courageous, energetic, inventive, and intelligent, invoking natural and sexual selection as justification, despite the lack of concrete data and biological assessment. His adamant assertions about the centrality of male agency and the passivity of the female in evolutionary processes, for humans and across the animal world, resonate with both Victorian and contemporary misogyny.

This presumably refers to the following passage on p.858 of the Descent:

“It is generally admitted that with women the powers of intuition, of rapid perception, and perhaps of imitation, are more strongly marked than in man; but some, at least of these, are characteristic of the lower races and therefore of a past and lower state of civilisation.

The chief distinction in the intellectual powers of the two sexes is shown by man’s attaining to a higher eminence, in whatever he takes up, than can woman – whether requiring deep thought, reason or imagination, or merely the use of the senses and hands.”

This was followed by (pp.859-860):

“These latter faculties [various mental traits] … will have been developed in man, partly through sexual selection… and partly through natural selection… Thus man has ultimately become superior to woman. It is, indeed, fortunate that the law of equal transmission of characters to both sexes prevails with mammals; otherwise it is probable that man would have become as superior in mental endowment to woman, as the peacock is in ornamental plumage to the peahen.”

This certainly shows that Darwin believed in the mental inferiority of women, and that this had, at least in part, an innate rather than cultural basis. This was the prevalent view at his time, which persisted until very recently (Fuentes’ institution, Princeton University, did not admit women until 1969, and my old Cambridge college only allowed the entry of female students in 1983).

However, Darwin strongly emphasized the importance of female choice in the evolution of sexual dimorphism in animals, so that Fuentes’ characterization of his views of the role of females in evolution is inaccurate. Darwin even extended it to humans (pp.914-915):

“Preference on the part of the women, steadily acting in any one direction, would ultimately affect the character of the tribe; for the women would generally choose not merely the handsomest, according to their standard of taste, but those who were at the same time best able to defend and support them. Such well-endowed pairs would commonly rear a larger number of offspring than the less favoured.”

Darwin’s theory of sexual selection was not well received, partly because of the emphasis on female choice, and (apart from R. A. Fisher’s advocacy in 1930), it did not start to receive serious attention from biologists until the late 1950s. Today, of course, it is recognized as a major factor in evolution, illustrating Darwin’s originality when he was able to free himself from prejudice.

Fuentes alleges that:

Racists, sexists, and white supremacists, some of them academics, use concepts and statements “validated” by their presence in “Descent” as support for erroneous beliefs, and the public accepts much of it uncritically.

I doubt that characters like Governor George Wallace and Sheriff Clark were much influenced by reading The Descent; in any case, most US racists probably do not believe in evolution.

Darwin scholars have discussed in great detail how a variety of ideologues of very different political persuasions have appealed to Darwin’s writings. Social Darwinism is, of course, notorious. On the other hand, Robert Richards, in his 1986 book (p.526), described how August Bebel, the 19th century leader of the German Social Democrats, thought that “capitalism put artificial restraints on the action of natural selection, so that the idiot son of the factory owner had the advantage over the talented son of the factory worker.” Bebel believed that “the natural forces of progressive evolution would produce a classless society in which property would cease to exist and women would not longer suffer political and sexual subjugation”. Other German thinkers, such as Ernst Haeckel, drew entirely opposite political conclusions; as Richards states (p.533), these contributed to the rise of Nazi ideology. But Richards adds that “The Nazi elite resisted evolutionary theory, despite its scientific charms. After all, could the Aryan race have descended from a tribe of baboons?”.

It seems that, unless you are an out-and-out creationist, you can interpret Darwin to justify almost any a priori belief.

Fuentes concludes by asserting that:

In the end, learning from “Descent” illuminates the highest and most interesting problem for human evolutionary studies today: moving toward an evolutionary science of humans instead of “man.”

First, “man” as used in the title of the Descent is a gender-neutral term referring to “humans”, as was common English language usage until recently.

Second, the last phrase suggests (perhaps unintentionally) that the modern evolutionary biology of humans has hardly moved on since Darwin’s day, and is still burdened with racial and sexist prejudices. This is a misleading caricature; while evolutionary biologists respect Darwin’s towering achievements in founding their field, they recognise that he (inevitably) was wrong about many things, most notably the mechanism of inheritance. There is a damaging confusion here between the views on certain issues of individuals who pioneered a branch of science, and the content of the science as it is currently practised and taught.

Brian Charlesworth

I get email

May 24, 2021 • 11:15 am

This email, which arrived this morning, is a real corker. I have redacted the name of the writer. Nothing else, including spelling and grammar, has been changed.

Here you go:

Foremost thank you for your time and patience. It’s a lot to take in but hope I can help you in a the smallest way possible.

Hi Jerry A Coyne I have read threw Why Evolution Is True for 3 years now. I came up with the conclusion , if we Did came from a species of apes , Do does species of apes come from a entirely diffirent species of apes ancestors . Why because the ape was not a chimpanzee or gorila ,etc
7 billion years is a long time giving for evolution to take place where we are here in the present moment. So evolution is very true in math.
DNA will only be diffident through he’s off spring from (DNA research the DNA change through the parents health condition good choices or bad choices health choices,)
Evolution takes place In both the mother and the father but did Darwin’s child plants ever create a new species of plants without a cross breathing without another species of plant.

I’ll stop there by
NAME REDACTED

Despite my arduous effort in a hard-to-brain situation, I find it impossible to make out what the writer is asking. It’s certain that there is a chain of primate ancestry in our history, and that different moieties of the primate lineage would be given different species names. I guess the guy (assuming we have a male) does realize that we are not descended from modern gorillas or chimps.

As far as the 7 billion years, well, Earth is only 4.5 billion years old, and evolution probably started around 3.5 billion years ago with the last universal common ancestor (LUCA). I don’t know what he means by saying “evolution is very true in math”.

I love the fact that DNA is “diffident”, which it more or less is, but of course that’s not what he means.

The rest is a mystery; evolution occurs in populations, not individuals, and although I don’t think Darwin created new species of plants, biologists have: by making auto- and allopolyploids.

At any rate, this is just one example of the mishigas that regularly tumbles into my inbox. Did the writer “help me in the smallest way possible”? I’m sorry, but NO.

How much variation in human behavior is due to variation in our genes? Answer: quite a bit.

May 24, 2021 • 9:45 am

The only people who claim that behavioral variation among people has nothing to do with their genes are ideologues: “pure blank slaters.” Based on studies of other species, we know that virtually all studies of traits that vary among individuals—be those traits morphological, physiological, or behavioral—show that some or even a lot of the variation in a population is based on variation in the genes of different individuals. (I know of only three studies in animals, out of thousands done, that failed to find a genetic basis for variation among analyzed traits.  Two of the three studies were mine, and all were on directional asymmetry: trying to see if there’s a genetic difference for, say, having more bristles on the right than on the left side of a fly.)

While humans have an extra source of inter-individual variation—culture—there are ways to get around cultural inheritance to see how much of human variation is based on genetic variation. There are several ways to determine and measure the contribution of genetic variation to variation among individuals.

First, though, let’s learn the technical term at issue: heritability. Heritability is a measure that ranges from zero to one (or 0% to 100%), and tells you how much of the observed variation among individuals in a population is based on genetic variation among those individuals.  The higher the heritability, the more genetic determination there is of variation in the trait. So, for example, if the heritability of human height for females is 0.7 (or 70%), that means that if you measure the variation in a population for height of women (the variation is conventionally estimated by calculating the variance—denoted by σ² or s²—then of the total variance for height, 70% of that estimate is due to variation of individual’s genes. In this case, there’s a high degree of genetic control of variation in height. (This is close to the actual figure for female height.) Confusingly, the symbol for heritability is h².

Now it’s a bit more complicated than this, for heritability incorporates only what we call the additive genetic variance rather than other kinds of genetic variance (usually minor). And course, there are other obvious sources of variation in height—most prominently nutrition and health.  The more that environment contributes to differences among individuals in a trait, the lower the genetic heritability. So, for example, the heritability of hair color among adults has been reduced by the introduction of an environmental source of variation: hair dyes. Less of the variation in hair color that we see, compared to, say, 200 years ago, is due to genetic variation.

It’s important to grasp several caveats about heritability. First, it is a figure that applies to one interbreeding population at one time—the time of measurement. You cannot apply heritability in one group to a different group that may have different genes and, importantly, different amounts and sources of environmental variation that affect a trait. A population undergoing famine, for example, may show a lower heritability of height because individuals’ heights may be altered by grossly different amounts of food they get.

Second, heritability says very little about how much a trait can be changed, for genetics isn’t destiny. Yes, the heritability of height may be 70%, but that doesn’t mean that we can’t make people bigger or smaller by feeding them a lot of good food, injecting them with growth hormones, or starving them. When people object to measuring heritability of IQ, for instance, they often mistakenly think that because IQ has a sizable heritability, which it does, it therefore can’t be changed. But that’s bogus; there are many possible interventions that can affect IQ.

Third, as implied above, measuring heritability within a group tells us very little, if anything, about the genetic basis of difference among groups. That’s because there may be environmental differences between groups that affect the character in profound ways and make extrapolations from one group to another useless. You cannot conclude, for example, that measures of behavior, mentation, and so on, in one population or ethnic group, even if the heritabilities are large within that one population, must therefore mean that big differences between groups must rest on genetic differences between those groups. The heritability of height in the Japanese population right after WWII, for example, was probably considerably smaller than 70% because of wide variation of nutrition in the Japanese. Thus you can’t conclude that their smaller height than Americans at the time was based on genetic differences. In fact, the average height of Japanese people went up three to four inches in about thirty years! So much for the idea that a substantial heritability for a trait in one group means that that trait can’t be changed!

Fourth, there’s a common misconception that heritability tells you “how much of your height (or weight, or IQ) is genetic”.  A heritability of 80% for height doesn’t mean that, if you’re five feet tall, four feet comes from genes and one foot from the environment. That conclusion is biologically meaningless since the height of an individual involves an interaction between genes and environment. The only sensible way to construe heritability is to say that it tells us how much of the VARIATION we see from individual to individual within a population is based on differences in their genes (or rather, forms of their genes: different “alleles”).

How do we determine heritability? There are several ways. In species like plants and animals in which we can perform artificial selection, we can estimate heritability by seeing how much a population responds to artificial selection for the trait. The bigger the response, the higher the heritability. There is an equation that tells you this: the response to artificial selection is roughly equal to the strength of selection (how much difference there is in the average trait in the group you choose for breeding and that of the population in general) multiplied by the heritability. If the heritability of head-to-tail length in pigs is 50%, and you choose for breeding a group of pigs whose average size is two feet longer than that of the population, you’d expect the next generation of swine to be one foot longer than the original population (0.5 X 2 feet). So if you know how strong you’re selecting, which you do, and what the response is in the next generation, you can back-calculate to estimate the heritability of the trait you selected.

Artificial selection isn’t practiced in humans, of course, so we usually determine heritability by looking at the correlation between relatives, including parent-offspring correlation and the correlation between twins. Parent-offspring correlation is dicey if there’s an environmental component to the trait that can also be inherited. I seem to remember that the two traits with the highest heritability in humans are religion and wealth, and that’s due to the passing on of these traits among generations via culture, not via genes!  In animals that have no transmissible culture, like fruit flies, one can, however, do these kinds of studies.

Humans researchers often use twin studies, comparing the similarity between identical twins (which have the same genes) with the similarity between fraternal twins, which share half their genes. We all know that identical twins are more similar for virtually every behavioral and morphological trait than are fraternal twins (just look at them!), implying that genes play a big role in these traits. You can in fact estimate the heritability of traits by looking at the difference in the correlations of identical vs. fraternal twins (you need a decent-sized sample of twins to do this).

There’s one caveat here, too, however. Identical twins often share more environmental commonalities than do fraternal twins. They may be treated more alike, dressed alike, brought up alike, and educated more alike than are fraternal twins. Thus an increased similarity of identical twins need not reflect the identity of their genes, but a greater similarity of their environments. At least for physical appearance, though, that doesn’t seem to be the case: you can’t “socialize” identical twins to look more alike than do fraternal twins!

One way around the possible environmental similarity is to compare fraternal twins raised together with identical twins separated at birth and raised apart. If the latter still show appreciably greater similarities despite their different environments, that’s a sure sign that the traits measured have substantial heritabilities. However, as you can imagine, there aren’t big samples of identical twins separated at birth.

Finally, we can measure heritabilities using DNA, by “genome-wide association studies”. This is more complicated, but involves finding those regions of the DNA associated with variation in a trait (like height), and then adding up the small effects of all known regions to see how much these known bits of the genome can contribute to variation among individuals. Heritabilities measured in this way are invariably smaller than those measured by correlations or selection, as the latter two methods take into account every region of the genome contributing to variation. Variation in most behavioral traits is due to many genes of very small effect, and it’s nearly impossible to find them all by association mapping.

This is all a very long prologue to a very short figure I’m going to show you—a figure that comes from this new paper in Nature Human Behavior. It summarizes heritability data for a number of behavioral traits, comparing heritabilities from twin studies to those from association studies. Click on the screenshot to see the paper, and I’ve put the full reference at the bottom:

And here’s Figure 2 showing the heritabilities measured both ways. Blue lines and dots give data from twin or family studies, orange lines and dots from association mapping.  You can see that association studies produce, as expected, lower estimates of heritability, but I’d expect the true values to be closer to the family-study data). 26 behavioral traits were measured, ranging from educational attainment, IQ as children and adults, amount of drinking and smoking, neuroticism, to mental disorders like schizophrenia.

Click on the figure to enlarge it.

The values in the colored triangle to the left are the “genetic correlations” between traits, which tells us the degree to which pairs of traits are affected by variation in the same genes. We need not concern ourselves with that.

For the moment, look at the lengths of the blue bars to the right, which are probably pretty close to accurate estimates of heritabilities. And for most traits they are pretty big, with over 25% of the variation in a trait due to variation in the genes within that population. For some traits, like adult IQ, number of sexual partners, alcohol dependence, autism spectrum placement, and schizophrenia, heritabilities are over 50%

What all this does is refute the “blank slate” view that the differences between people in their behavior is completely due to culture and socialization. It also shows that a substantial portion, however, is due to other sources of variation: developmental, post-birth environmental differences, and so on.  It also shows that you could select on any of these traits and get a response, increasing, for instance, the age of first intercourse (Christians take note!) or reducing alcohol dependence. NOTE: I AM NOT SUGGESTING THAT WE SELECT ON THESE TRAITS!

So have a look—and click on the figure!

____________

Abdellaoui, A. and K. J. H. Verweij. 2021. Dissecting polygenic signals from genome-wide association studies on human behaviour. Nature Human Behaviour. https://doi.org/10.1038/s41562-021-01110-y

“Hooker’s Arch”: A post by Andrew Berry

May 21, 2021 • 1:00 pm

My friend Andrew Berry, a lecturer and advisor at Harvard’s Museum of Comparative Zoology and the Department of Organismal and Evolutionary Biology, sent me a nice email that I asked him to turn into a post for me. He kindly obliged. Darwin’s Arch, which recently collapsed in the Galápagos Islands, was described in a NYT article. Here’s the original landmark

. . . and after its collapse on May 17:

Andrew knew a bit of a parallel, which he describes below. Andrew’s words are indented.

by Andrew Berry

I saw your mention of the recent collapse of ‘Darwin’s Arch’ in the Galápagos.

Here’s a nice parallel.  One of Darwin’s key offsiders was Joseph Dalton Hooker (the middle name serves to distinguish him from the US Civil War general—definitely not a Darwin confidant). Hooker was one the era’s leading botanists, and was for many years the director of Kew Gardens.  In 1844, Darwin chose to confide in Hooker about his heretical ideas. This, for Darwin, was a big deal: he had been quietly and privately nurturing his evolutionary schemes more or less since the return of the Beagle in 1836 and he felt in need of a scientific sounding board.  He was still a long way from being ready to go public: it wasn’t until 1858, 14 years later, that A. R. Wallace’s intervention forced his hand on this.  Darwin’s famous letter to Hooker states, “I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable”.

Hooker

One of the reasons Darwin picked Hooker for this role was that, like Darwin, Hooker had considerable expedition experience.  They both accordingly had a global perspective on biogeography.  Specifically, Hooker had gone on the James Clark Ross Erebus/Terror expedition (1839-43) that established a key early benchmark for the exploration of Antarctica. Roald Amundsen, the great Norwegian polar explorer (who beat Robert Falcon Scott to the South Pole in 1911) pulled no punches about the expedition’s significance:

“Few people of the present day are capable of rightly appreciating this heroic deed, this brilliant proof of human courage and energy. With two ponderous craft – regular “tubs” according to our ideas – these men sailed right into the heart of the pack [ice], which all previous explorers had regarded as certain death … These men were heroes – heroes in the highest sense of the word.”

En route to Antarctica, the expedition’s first major port of call was Kerguelen Island, which is about as far from anywhere as you can get on planet Earth — central far south Indian Ocean.

Arriving in May 1840, the expedition spent two and a half months there before heading on to Tasmania, and, from there, Antarctica.  Kerguelen was thus the first place in which the young Hooker (he was 22 at the time) got to analyze and describe a previously largely undescribed flora.  That things turned out this way is a truly remarkable coincidence.  Late in life, Hooker recalled being raised as a boy on tales from James Cook’s voyages.  In particular, little Hooker had been impressed by this image from Cook’s 1776 visit to Kerguelen (the islands were formally discovered four years previously by a Frenchman, Yves-Joseph de Kerguelen-Trémarec). Note the impressive natural arch on the horizon at the far left of the image.

Here’s what Hooker wrote:

“When still a child, I was very fond of Voyages and Travels; and my great delight was to sit on my grandfather’s knee and look at the pictures in Cook’s ‘Voyages.’ The one that took my fancy most was the plate of Christmas Harbour, Kerguelen Land, with the arched rock standing out to sea, and the sailors killing penguins; and I thought I should be the happiest boy alive if ever I would see that wonderful arched rock, and knock penguins on the head. [JAC: Hooker should be canceled for thinking that!] By a singular coincidence, Christmas Harbour, Kerguelen Land, was one of the very first places of interest visited by me, in the Antarctic Expedition under Sir James Ross.”

What is the relevance of all this? Because, some time between 1908 and 1913, the arch on Kerguelen that so thrilled Hooker went the way of Darwin’s Arch.  Happily the ideas of both Darwin and Hooker have proved more resilient than the landmarks they’re associated with.

Torygraph exaggerates Darwin’s evil in trying to smear Sheffield’s “decolonized” biology curriculum; and a bonus guest take by Andrew Berry

May 10, 2021 • 9:15 am

The article below appeared in the Torygraph two days ago, and, although there is some truth in what it says about Darwin’s views, the gap between the Torygraph’s rhetoric and the reality is substantial.  Click on the screenshot to read it; and if it’s paywalled just make a judicious inquiry. I’m not sure, not being a reader of this paper, whether they are impugning Sheffield University, Darwin’s theories, or both.

You can read for yourself the claim that Darwin’s theory justified white male superiority (yes, he believed in male superiority and in the hegemony of whites, but it was the paternalistic racism of Victorian times, and note that Darwin was also an ardent (and rare) abolitionist). At any rate, here’s a brief excerpt of the Torygraph article, which summarizes a University of Sheffield handbook on “decolonizing biology”:

Charles Darwin is among “highly celebrated scientific figures” who “held racist views” because he used his theory of natural selection to justify white male superiority, according to a new university’s handbook for teaching and research.

The renowned naturalist is on a list of 11 feted scientists whose views “influenced the type of research they carried out and how they interpreted their data”, according to Sheffield University’s guide drawn up to decolonise the biology curriculum.

This is despite Darwin’s fervent support for the abolition of slavery, which he called a “sacred cause”, unlike many of his contemporaries. He said of slavery that “it makes one’s blood boil”.

The handbook, seen by The Telegraph, tells students and lecturers that he must be historically caveated when lecturers teach his seminal theory of evolution.

Historians told The Telegraph that Sheffield’s guidelines were “unhistorical and misleading” and “authoritarian”.

The Russell Group university has also told science students and lecturers in the guidance to drop the terms “founding father”, “idols” and “geniuses” to avoid “hero worshipping” scientific figures.

This practice treats them as “white saviours” and erases less privileged scholars, it explains. Drawn up by lecturers in the Animal and Plant Sciences faculty, the guide says “whiteness and Eurocentrism of our science” must be dismantled.

“It is clear that science cannot be objective and apolitical,” it adds, and “the curriculum we teach must acknowledge how colonialism has shaped the field of evolutionary biology and how evolutionary biologists think today”.

. . . . According to Sheffield’s decolonised curriculum, Mr Darwin “believed that his renowned theory of natural selection justified the view that the white race was superior to others, and used his theory of sexual selection to justify why women were clearly inferior to men.”

It says his voyage on HMS Beagle, when he collected plant and animal samples, was to map colonies.

Some of the “colonialism” refers to the two voyages of the Beagle, but those voyages were not meant “colonize” or map nonexistent British colonies, but to map the coast of South America for trading purposes and for ship re-stocking, including making diagrams of the ports.

If you’ve read The Voyage of the Beagle and the Descent of Man, you will realize that yes, Darwin had racist tendencies that would be seen as insupportable today, but then it’s doubtful, to me at least, that Darwin would be a racist if he lived in modern times. And his fight for abolitionism must surely be taken into account. You can have racist ideas and be an abolitionist at the same time: humans are multidimensional. To impugn Darwin’s theory because of his views, as the Torygraph seems to be doing, is surely to engage in an ad hominem argument, placing Darwin in company with Hitler, Stalin, Mao, and others shown on the cover of this creationist book by the Turkish liar (and now criminal) Adnan Oktar (pseudonym Harun Yahya). (h/t: Andrew Berry)

To be sure, the article does quote real Darwin scholars who think that this “decolonization” was ridiculous:

But Prof James Moore, a biographer of Darwin and historian of science, told The Telegraph: “Almost everyone in Darwin’s day was ‘racist’ in 21st century terms, not only scientists and naturalists but even anti-slavery campaigners and abolitionists.

“What set his ‘racism’ apart – and makes him more like us today – was his profound conviction that all the human races are ‘family’, sisters and brothers.

“Darwin’s wokeness was most obvious in his maintaining the full common humanity and unity of the races in the face of a rising anthropology that insisted the races were in fact separately originated and unrelated species, thus offering justification of atrocities that Darwin is now blamed for.”

Prof Nigel Biggar, an Oxford historian, added: “During Darwin’s lifetime the British Empire was busy emancipating slaves across the world.

“The ‘decolonising’ assumption that ‘colonial mapping’ was all about oppression is false, and the judgement that Darwin should be damned by association is morally stupid.

“Before propagating this ideology, did Sheffield University secure the consent of academic staff, and does it now allow for conscientious objection? If not, its conduct is authoritarian and arguably a violation of academic freedom.”

After some effort, I managed to locate the handbook that Sheffield University uses as its “decolonization guide”. You can download it here, and yes, it does make some statements similar to what the Torygraph says.  Here are two excerpts; I won’t bother to analyze them here:

This sentence is palpably ridiculous:

Many prominent evolutionary biologists and geneticists who helped establish the field were racists and eugenists, including JBS Haldane, Francis Galton, James Watson and many more. Their theories served as justification for slavery and mass slaughter.

Haldane was not a racist, Galton, who advocated class-based eugenics (based on encouragement of breeding), had no influence in affecting eugenics or “slavery and mass slaughter”, and Watson, who is a racist, has had no influence on slavery, white supremacy, or “mass slaughter.” How cold he have? He’s still alive. He is in fact disgraced and was removed from his position at Cold Spring Harbor.

And there’s an analysis of the malefactors of evolutionary biology, like this one:

So the Torygraph doesn’t have it all wrong, but it clearly implies that Darwin’s theories, which indeed were used by others to justify oppression and white superiority, are in themselves deficient because of how they were employed. But the misuse of a theory doesn’t mean it’s wrong—only that others bent it to suit their ideology, as Adnan Oktar did. Few biologists (and those would be creationists) doubt the immense power of the theory Darwin suggested in 1858 and published in 1859.

I myself would not teach evolution along the lines of the University of Sheffield, which gives the whole thing a political slant, ignoring the tremendous advances that Darwin forged in our thinking. How relevant are Darwin’s views to teaching evolution, anyway? Was any Victorian Englishman perfect by modern lights? And must we always bring in people’s moral views which, perhaps conventional in their times, are now odious in ours? These are questions we’ve discussed before, and will discuss again—perhaps today—but rather than sling mud at Darwin, I want to give a measured take on Darwin and the Torygraph piece by my friend and colleague Andrew Berry, a lecturer and adviser in evolutionary biology at Harvard. So voilà, and many thanks to Dr. Berry for allow me to twist his arm:

Guest comments by Andrew Berry

Rather than pushing back reflexively on Sheffield University’s statements on Darwin (as reported by The Daily Telegraph), I think it’s worth taking a serious look at the suggestions being made.

  1.  Darwin 

Darwin comes up short, no question, in any retroactive 21st century assessment of his views on human race and gender.  He was, by today’s standards, a racist and a misogynist. But of course his views were a product of where and when he lived; his opinions on race and gender were derived from the upper-class white world he inhabited.   That he was actually downright progressive — he was a fervent abolitionist, for example — by the standards of this world is irrelevant. We have to ask whether his scientific ideas — his legacy — are in some way tainted by his thinking in these areas.  Is the theory of evolution by natural selection inherently racist or sexist?  In some of their attempts to characterize their objections as being based on more than religion, some creationists insist that it is.  And it’s certainly true that plenty of dubious figures have hijacked Darwin to provide a veneer of scientific respectability to their prejudices.  But the theory itself?  It’s essentially based on two observations: the capacity of populations to undergo exponential growth, and the occurrence of mutation — error — in the transmission of genetic information from generation to generation.  Exponential growth in a world of finite resources results in competition, with that competition being won by, on average, the genetically best endowed members of the population.  I for one don’t see racism or sexism embedded in these assertions.

There is no question that Darwin’s thinking was inspired by the milieu in which he lived — Malthus’s ideas were au courant, and Victorian Britain was an early experiment in laissez-faire capitalism — but Darwin’s identification of a mechanism of evolutionary change should absolutely not be taken as an endorsement on his part of the kind of social darwinism that some of his supposed heirs came to embrace.  To assume that the processes we observe in the natural world somehow offer a prescription for how we should live our lives is to commit the naturalistic fallacy. 

  1.  History of Science

Historians of science have long objected to popular simplifications of the scientific process.  Newton encounters a falling apple, and — bingo! — the theory of gravitation is born.  This tendency to embrace simplifications has two consequences: a focus on the individual (the scientific “genius” responsible for the breakthrough), and, correspondingly, a failure to take into account the underlying factors — social, or otherwise — involved in the development of innovations.  This simplified discourse is promoted by institutions like the Nobel Prize.  The lab head gets the prize.  What about all those post-docs, colleagues, grad students who contributed?  Science, in reality, is a complex, messy business that does not lend itself to handy Eureka! moment narratives.  In short, all Sheffield University’s guidelines are stating is that we should move on from the Nobel/Eureka! model of understanding the scientific process and become instead better informed historians of science.  Let’s therefore think about the unsung heroes and about the non-scientific factors that together conspired to make a previously inaccessible idea accessible.

Curiously, Darwin and evolution offer a wonderful case study.  Evolution by natural selection is a simple and powerful idea that explains features of the natural world — design in nature, biological diversity, us — that every society has sought to understand (typically through its own set of creation myths), and yet it was not until the middle of the 19th century that the idea was finally formalized.  And it was formalized by two people, not one.  A R Wallace does not get anywhere close to the air time that Darwin gets [had the Nobel Prize existed in their day, Darwin would have received the Prize, Wallace a gentlemanly shout-out in Darwin’s acceptance speech], but the original publication of the theory (1858) took the form of two separate statements of the same idea — one by Darwin and one by Wallace.  Maybe Wallace isn’t the best example of the scientific also-rans that Sheffield University is asking us to note — he was white and male, after all — but his story illustrates the point well, and some part of his eclipse by Darwin in our histories of the theory is attributable to his relative poverty and lack of connections.

The Darwin-Wallace story is an instance of London bus syndrome: you wait and wait in the rain for one to come, and then, suddenly, two arrive.  Darwin and Wallace discovered the same idea independently and (more or less) simultaneously.

How on earth did that happen?  Darwin and Wallace were subject to the same set of socio-cultural influences. These gave them special opportunities and shaped their ideas in particular ways (relative to earlier thinkers in the same area).  Some of those influences/opportunities: Malthusian thinking, which was often invoked as Victorian Britain pondered creating a societal safety net; laissez-faire economics, which enshrines the improvement-through-competition essence of natural selection; natural theology, which invited empirical scientific research (with a view to understanding the ways of the creator); the industrial revolution, which suggested that living things may be nothing more than very complex machines; British imperialism, which allowed both Darwin and Wallace to travel the world and to see biological diversity in situ.  All these factors — and more — lie behind that 1858 joint paper.  My point: to understand the development of these ideas, the focus should not be on Darwin and Wallace, but, rather, on these other factors.

I don’t think that Sheffield University’s guidelines warrant The Daily Telegraph‘s outrage.

A.) We should indeed review our scientific ideas to ensure that elements of past pernicious thinking have not been woven into the fabric of those ideas

B.) We should of course condemn corruptions of scientific ideas that are used to motivate injustice.  Social darwinism is not an inevitable corollary of the theory of evolution by natural selection

C.) We should indeed try to reduce our reliance on the ‘Great Man’ narrative in history of science.  Scientific discovery is a complex business, and, for sure, the history of science is littered with Rosalind Franklins who have received less credit than they deserve

And from PCC(E), here’s a photo of Andrew on top of Mount Darwin in California, about to place a copy of Why Evolution is True, autographed by yours truly, at the summit for future generations to find. . .

Bdelloid rotifers, once the poster group for having no sex, now thought to have been bonking on the sly

April 18, 2021 • 1:00 pm

One of the mysteries of evolutionary biology is the existence of groups of eukaryotic animals (animals with true cells) who don’t appear to have sex. These include some ostracods, mites, and stick insects, as recounted in the first paper below, which came out last year.

But the biggest mystery of all is a group that’s been studied for years (the first individual was described by van Leewenhoek in 1677): the bdelloid rotifers, a class of rotifers (rotifers constitute a phylum) which have never been known or seen to have sex. Laine et al., in the second paper below, estimate that at least half a million bdelloid individuals have been examined by biologists over the years, and not one male has ever been found. Nor has copulation or anything that looks like sex ever been seen. Every individual of the group is a female who produces eggs by parthenogenesis (asexual reproduction). The group is about ten million years old, and sex was a property of its ancestor, which we can see by showing that its relatives all reproduce sexually, implying that bdelloids lost sex secondarily. But why? Who knows? What we’re concerned about here is whether they really are, as all the textbooks say, totally asexual.

Bedlloids are small but multicellular, and possess, despite being only a few tenths of a millimeter long, “ganglia, muscles, digestive, excretory, reproductive and secretory systems; photosensitive and tactile sensory organs, and structures for crawling, feeding, and swimming.” (From Laine et al.)

Here’s what one looks like, it’s an individual of Adineta vaga, the subject of the first study below:

So are they really totally asexual? If that were the case, it would be an evolutionary puzzle because if you can’t reproduce by mingling your genes with those from other individuals, you are impeded from combining adaptations occuring in different individuals, and that hinders evolution. Suppose one female has a mutation for heat tolerance and another individual for salt tolerance. If your environment became hot and salty, sexual individuals could mate and get both genes together; but this combination cannot happen in the absence of sex.

Asexuality is thus thought to be an evolutionary “dead end”, and most such lineages haven’t thrived over evolutionary time, usually going extinct. (The origin of sex is also a mystery, for if you’re parthenogenetic, you can leave twice as many of your genes compared to those who bequeath only half their genes to any offspring. But we’ll leave that conundrum, called “the cost of sex”, aside for now.)

The fact is that nearly all species of animals, and most plants, have sex, and once you have it, it makes good evolutionary sense to keep it.

But why have the bdelloids persisted for so long?

One suggestion, which was supported by a bit of genetic data a decade or so ago, is that they’re actually having sex on the sly—they are, to take a term from evolutionist John Maynard Smith, “sneaky fuckers”. The problem is that if this is true, as the two new papers below suggest, WHERE ARE THE DAMN MALES?  Well, we don’t know, and neither do the authors of these papers.

The two papers (the second is unpublished yet) use DNA sequencing to look for signs of sex in the sequence of the genome. The first paper (click on screenshot, pdf here and reference below) sequenced complete genomes taken from 11 individuals of A. vaga.

This second paper, from bioRχiv (pdf here), did the same thing, but with fewer isolates and using a different species of bdelloid, Macrotrachella quadricornifera. You may recognize the last author, Matt Meselson, a very famous biologist whose 1958 work with Frank Stahl (called “the most beautiful experiment in biology”) showed that DNA replicates by unzipping and synthesizing a new single strand on each of the unzipped original strands (“semiconservative replication”). For that, they should have won a Nobel Prize, and it puzzles me why they didn’t.

And now here we are 63 years later, and Matt (a terrifically nice guy) is still going strong, but has been working on sex in rotifers as a new area. Fertile minds find fertile areas of inquiry.

The upshot is that both studies suggest, in different ways, that bdelloids do have sex, for genetic patterns indicate that different individuals have recombined their genes over time. The sneaky sex isn’t frequent—once every 10 to 100 generations estimated in the first paper and at least one sexual event in the last 100-200 generations in the second sample.

The genetic data suggesting meiosis (formation of gametes) and recombination, both features of sexual reproduction, include these observations:

a.) The occurrence of genotypes (combinations of genes) in “Hardy-Weinberg” proportions, which can occur only by sexual reproduction.

b.) The appearance of mixing of genes along chromosomes, so that the farther two genes are apart on a chromosome, the more likely they are to not be associated with each other. This is a pattern you’d expect with sexual rather than clonal reproduction, as clones show complete association of genes along chromosomes since no recombination occurs. Recombination tends to break up gene combinations, and the farther the genes are apart on the chromosome, the more often this happens.

c.) Different combinations of genes show different “family trees” or phylogenies, which again is not expected under clonal reproduction because, since all genes are permanently frozen in one genome, they should all evolve together by mutation and selection, and should thus show the same family tree.

d.)  The appearance, in the second paper, of patterns of genetic variation that makes the different clones appear to be genetic relatives formed by sexual reproduction. This pattern: rotifers from different places share big segments of DNA at many places along the genome, but not at many others, a pattern expected with recombination occurring during sex but not clonal reproduction.

Now two other processes could in principle produce the appearance of sex when it doesn’t really occur: horizontal gene transfer (HGT), in which vectors like viruses or bacteria take DNA from an individual and inject it into another one. This could create patterns looking like sex but doesn’t involve gametes being formed and uniting to form zygotes.

The other is gene conversion, in which one gene can turn the other copy on a sister chromosome into its own type.  I won’t get into the gory details, but both authors have pretty strong arguments about how these two non-sex-processes CANNOT explain the DNA-sequence data.

Now this group isn’t like animals that have to have sex every generation: bdelloids usually reproduce clonally but appear to rarely have sex. The big question is the one above; if they’re really having sex, and it damn well looks like it, where are the males?  Is there some cryptic way that sex can occur without us being able to find the males? Laine et al. suggest that males might appear very sporadically, perhaps “confined to only a short interval during a population bloom [rapid expansion], therefore requiring frequent sampling for their detection.”

So, as happens so often, the mystery has deepened. We still don’t know why bdelloids are mostly clonal, and we still haven’t seen males, but now we think they do have sex from time to time. We just don’t know how. OR there may be some mysterious way of mixing your genes with other individuals without having HGT or conventional sex.

As for the sexless ostracods, stick insects, and mites, well, they haven’t been studied very closely.

Stay tuned.

________________

Vakhrusheva, O.A., Mnatsakanova, E.A., Galimov, Y.R. et al. Genomic signatures of recombination in a natural population of the bdelloid rotifer Adineta vaga. Nat Commun 11, 6421 (2020). https://doi.org/10.1038/s41467-020-19614-y