I completely forgot about Sunday’s Faux Duck O’ the Week, being occupied yesterday with The Auction and all. But better late than never, and here’s the latest in biologist John Avise‘s series of waterfowl that resemble ducks but aren’t. Can you guess this species?
His captions and Fun Duck Facts are indented. (To see the ID, Fun Duck Facts, and range map, go below the fold.)
The two male wood ducks (Aix sponsa) in Botany Pond are still here, though the Lady Woodie flew the coop. And the two males, who get plenty of noms from us, are starting to change their plumage from the non-breeding form to the fantastic breeding coloration.
Here are the woodies on September 16. This first one is a male:
In the photo below, the one on the right with the pink beak is a male, while the one on the left, with the gray beak, is the female, now departed. The creature in the rear is not a duck.
Here are the two males today. Their heads are turning iridescent green, their wings blue, their beaks red, and they’re getting a lovely stippled chest pattern, as well as their cherry red eyes:
Head starting to green up. For the endpoint, see the last photo:
The pair of males, who are named Frisky and Blockhead, like to perch on the knees of the cypress tree. After all, they’re perching ducks and like to have wood under their feet. I like to think they’re brothers. They’re nice and plump, too, as we feed them well.
If we keep them around for another short while, they should wind up looking like this (picture from Wikipedia). Ah, the marvels of sexual selection and development! I really want to see this happen:
Oh, and Honey is still around, continually asserting her alpha-female status by attacking other mallards at feeding time.
UPDATE: I left this comment after the Slate piece, but it appears to have been removed. I’m not sure why, as there are far more vitriolic comments in the thread.
The claim that the idea of cooperation is novel and paradigm-shifting in evolutionary biology is palpably ridiculous. All of the examples given by the author are not only known, as well as many other examples of mutualism that long preceded Margulis (lichens, termites, cleaner fish and “cleanees”), but fit firmly within the neo-Darwinian paradigm. There’s nothing new here except the author’s claim that the idea of cooperation is novel. To anybody who’s studied evolutionary biology, this is nonsense. Further, the author apparently hasn’t read Prum, who actually tried to RESURRECT Darwin’s idea of sexual selection.
I have written a long critique of this piece at my website http://www.whyevolutionistrue.com. It’s the latest piece, and since I may not be allowed to post links, just go to my site and read it. The upshot: this piece evinces either ignorance or deliberate obfuscation, and is also misleading in that it tries to distort the history and nature of evolutionary biology in the service of an ideology (apparently socialism).
Once again we have a collision between ideology and science, but in this case the perceived conclusions of science are in fact wrong, so the called-for revision of evolutionary biology in light of woke ideology isn’t needed. In a new article in Slate (see below), John Favini argues that evolutionary biologists are completely wedded to the paradigm of competition between individuals and between species, and further argues that the idea of individuals or species being cooperative is both reviled, new, and non-Darwinian. If you’re at all familiar with the history of reciprocal altruism, kin selection, and mutualism between species, you’ll know that these ideas—which all involve the evolution of cooperation—are both over half a century old and well ingrained in modern evolutionary theory.
But Favini is either unfamiliar with this literature, which is inexcusable for a graduate student in anthropology who claims a knowledge of biology, or hides it, which is duplicitous. I won’t make a judgment except that this article, which seems more attuned to the Discovery Institute (or even Salon), doesn’t belong in Slate, which is supposed to be a decent site. (Hitchens used to write for it.)
Favini is identified at the site as “a Ph.D. candidate in anthropology at the University of Virginia and a freelance writer. He is interested in climate change, environmental politics, and science as a cultural domain.”
From this you can derive one speculation and one conclusion. The speculation is that Favini is a cultural rather than a physical anthropologist; the former tend to be social justice warriors who often downplay scientific facts in favor of their ideology (they often, for example, completely dismiss the idea of “race”, though it has a qualified reality that’s meaningful). Second, the “science as a cultural domain” bit is worrying, and in fact is what gave rise to the Slate article (click on screenshot below to see it).
Favini situates Darwin at the outset as a white, elite, Englishman subject to the social forces of his time, and predisposed to think about competition because his theory of natural selection originated after reading Malthus on competition. From this, throughout the article, he concludes that all of Darwinism, then and now, is marinated in the idea of competition.
. . . like all humans, Darwin brought culture with him wherever he traveled. His descriptions of the workings of nature bear resemblance to prevailing thinking on human society within elite, English circles at the time. This is not a mere coincidence, and tracing his influences is worthwhile. It was, after all, the heyday of classical liberalism, dominated by thinkers like Adam Smith, David Hume, and Thomas Malthus, who valorized an unregulated market. They were debating minor points within a consensus on the virtues of competition. In an especially humble (and revealing) moment, Darwin characterized the principles underlying his thinking as naught but “the doctrine of Malthus, applied with manifold force to the whole animal and vegetable kingdoms.”
. . . More than just a cliché, though, the supposed naturalness of competition has played a central role in substantiating the laissez-faire variety of capitalism the majority of the American political spectrum has championed for the past four or so decades. Indeed, any non-market-based solution to social issues usually falls prey to claims of utopianism, of ignoring the fundamental selfishness of the human species. . . . To put it simply, we have let Darwinism set the horizon of possibility for human behavior. Competition has become a supposed basic feature of all life, something immutable, universal, natural.
Regardless of the idea of “social Darwinism” (which Darwin never held and which has been completely abandoned by intellectuals), the facts of competition between genes (i.e., natural selection), competition between individuals (which produces natural selection), and competition between members of different species (which also produces natural selection as well as interesting aspects of ecology) are real and important. In fact, without competition between the different forms of genes for representation in later generations, we wouldn’t have natural selection at all!
And to the extent that natural selection is responsible for most interesting features of life, including biodiversity itself, it is “natural and universal.” But “natural” doesn’t mean that we have to put up with it, for we derail natural selection all the time by using doctors, dentists, and optometrists, and by using contraception. Further, we’ve tamed competition between individuals with laws against aggression, rape, and so on. Finally, we’re beginning to tame the competition between species by removing invasive species from places they don’t belong and by giving up the foolish idea that we humans should dominate all of nature.
Why is Favini attacking competition at such great length? We get a clue early in the article, as well as later. Early on, he says this:
Yet new research from across various fields of study is throwing the putative scientific basis of this consensus into doubt. Mind you, there have always been people, scientists and otherwise, who conceived of life outside a Darwinian paradigm—the idea of evolutionary biology is and has been a conversation among a mostly white and male global elite. Yet, even within centers of institutional power, like universities in North America, competition’s position as the central force driving evolution has been seriously challenged recently. In fact, criticisms have been mounting at least since biologist Lynn Margulis began publishing in the late ’60s.
You guessed it. It’s those damn white males, again, Jake! They are the ones with the power to push an unwarranted consensus about competition in the “elite universities.” According to Favini, it took a female, Lynn Margulis, to dethrone competition as the centerpiece of evolutionary biology. Well, that’s not quite true, because Darwinian speculations about cooperation, and the recognition that evolution can promote it both within and between species, has been an accepted part of evolution well before Margulis found that a form of “cooperation” was responsible for the advent of the eukaryotic cell. Later on, we’ll hear Favini touting the “heterodox voices” of indigenous Americans as helping dethrone the idea of competition, a woke concept that, sadly, isn’t true, either.
Favini then bangs on at length about all the supposedly non-Darwinian instances of cooperation that he says, have “fractured Western biology’s consensus on Darwin”. This is, to be gauche, pure bullshit. Most of these phenomena have been known for decades, and none of those pose any kind of challenge for Darwinism. They include the merging of two prokaryotes into a cell containing mitochondria, and, in plants, a cell containing chloroplasts. This “endosymbiosis” idea was a wonderful and true hypothesis pushed (but not originated) by Lynn Margulis. And it can be seen as an example of cooperation, in which the “big” cell benefits from having energy-generating organelles, while the organelles (which, like the cell itself, underwent evolution to promote the interaction) gain protection and sustenance.
Margulis’s theory was initially met with some resistance, but was quickly accepted after microscopic and especially DNA evidence showed that she was right. But the important thing in our discussion is that this is just one example of the kind of symbiosis that was accepted long before Margulis. Well known symbioses include those between leafcutter ants and fungi, between the termites and the protists and bacteria that help them digest cellulose, between the algae and fungi that constitute lichens, between cleaner fish and the “cleanees,” between clownfish and the sea anemones they inhabit, and the many species that have symbiotic bacteria or algae, like the bacteria that inhabit light organs and produce light in deep-sea fish (see photo at bottom).
It’s important to recognize that these examples of interspecific symbiosis (“mutualisms,” in which both partners benefit), are perfectly consistent with neo-Darwinism, and have never been seen as a challenge to the theory. Each species benefits from associating with the other, and natural selection will act and has acted to tighten the mutualisms. More recent findings of a mutualistic “microbiome” in ourselves and other species are also something that slots perfectly into a Darwinian paradigm, just as does another form of symbiosis: parasitism.
I’ll add here that cooperation within groups, beginning with kin selection that forges bonds between relatives (and explaining the wonderfully cooperative castes within a social-insect colony), and extending to “reciprocal altruism”, in which small bands of animals undergo individual selection to treat their groupmates better, has also never been problematic for Darwinism. With the recognition by Hamilton, Trivers, and others that genes in you are also genes in your relatives, and that genes for scratching the backs of others who scratch yours can also be advantageous, the multifarious forms of cooperation in nature have developed into a wonderful story and a true story, but also, contra Favini, an old story.
Favini, however, pretends that all this work on cooperation has upended evolutionary biology, fracturing our consensus on Darwinism. Given that all the examples he adduces haven’t tarnished evolutionary theory one bit, he’s just reaching wildly to pretend that he’s found something new. He even cites the renegade “Third Way” group of evolutionists who, to my mind, don’t pose any serious alternative to Darwinism:
Put simply, life is beginning to look ever more complex and ever more collaborative. All this has fractured Western biology’s consensus on Darwin. In response to all these new insights, some biologists instinctively defend Darwin, an ingrained impulse from years of championing his work against creationists. Others, like Margulis herself, feel Darwin had something to offer, at least in understanding the animal world, but argue his theories were simplified and elevated to a doctrine in the generations after his passing. Others are chartering research projects that depart from established Darwinian thinking in fundamental ways—like ornithologist Richard Prum, who recently authored a book on the ways beauty, rather than any utilitarian measure of fitness, shapes evolution. Indeed, alongside the research I have explored here, works by scientists like Carl Woese on horizontal gene transfer and new insights from epigenetics have pushed some to advocate for an as-yet-unseen “Third Way,” a theory for life that is neither creationism nor Neo-Darwinian evolution.
Note that Favini gives Darwin only a bit of credit here, saying that “Margulis [felt] Darwin had something to offer.” DUHHH! And as far as Prum’s book on sexual selection for “beauty” goes, well, as you may recall, in that book Prum revives Darwin’s own theory of sexual selection! Did Favini even read the book? While Prum grossly exaggerates the ubiquity of and evidence for the “runaway” model of sexual selection, make no mistake about it: Prum’s theory is thoroughly Darwinian, incorporating Favini’s despised “utilitarian measures of fitness.” (Just look at the theoretical models of runaway sexual selection.)
I’ll add, to complete the record on Darwin, that he did not ignore cooperation. In The Descent of Man, for instance, he speculates on the origin of human altruism, although he floats a theory of group selection to explain it. He also ponders the evolution of cooperation in social insects, and, in the chapter on “Instinct” in The Origin, suggests that sterile castes can be produced by “family selection,” which many have taken to be one of the first inklings of kin selection among relatives.
It’s at the end of the piece that Favini’s mask slips as he plunges into wokeness, touting the insights of indigenous Americans (which haven’t influenced evolutionary theory), and then dissing capitalism, which he sees as the outcome of Darwinism rather than of economic and social forces.
First, the indigenous people:
This lack of agreement isn’t such a bad thing. Leaving the Darwinian consensus behind means a more capacious, diverse, and ultimately more rigorous science. The recent dissensus has opened up more room for important, heterodox voices like Robin Wall Kimmerer, a botanist and member of the Citizen Potawatomi Nation. Kimmerer speaks of plants as highly intelligent beings and teachers, a sharp departure from the reductionist, utilitarian approach to plant and animal life that passed as scientific rigor within the Darwinian framework. Much of the recent research I have highlighted might count as what Kim TallBear, a scholar and enrolled member of the Sisseton-Wahpeton Oyate, calls “settler epiphanies”—belated “discoveries” by settlers of Indigenous knowledge that was either ignored or outright suppressed by colonial land appropriation and attempted genocide.
Certainly ethnobotany and the knowledge of indigenous people included in that field, have been extremely valuable. A huge proportion of our drugs, for example, come from plants, some based on how they were used by locals. But indigenous peoples haven’t changed the scientific “way of knowing” with their “spiritual way of knowing” (something that Kimmerer seems to tout), nor have they made Darwinism swerve even a millimeter from its path. (Note Favini’s denigration of evolutionary biology as “reductionist and utilitarian”. It is of course neither.)
Finally, Favini lapses into socialism. But whatever its merits, socialism cannot and should not be justified by citing the evolution of cooperation, or by arguing that an unjustified view of evolutionary biology has severely impeded its acceptance by propping the notion that capitalism’s competitition is “natural” Social Darwinism might have been mildly influential at the time of Herbert Spencer, but that view has long since fallen by the wayside.
Overall, then, what we get in Favini’s piece is pure politics, with some Darwinism thrown in to demonize and blame for competition:
Far too many environmentalists assume that people, driven by innate self-interest, are bound to harm ecology, that we will inevitably clear-cut, extract, consume, so long as it gives us an advantage over the next guy. This leaves us deeply disempowered, with few solutions to climate change outside limiting humanity’s impact through some kind of population control. When competitive self-interest is revealed to be a mutable behavior, the causes of climate change come into greater clarity: not human nature, but an economic system that demands competition, that distributes resources such that a tiny elite can live tremendously carbon-intensive lifestyles while the rest of us struggle for a pittance. Leaving competition behind, we can also imagine richer solutions: climate policies that problematize the tremendous wealth of the few, that build economies concerned with collective well-being and sustainability.
. . . Science can play a critical role in liberating our imagination from competition’s grip. It can show us all the symbioses that make life possible. Such a science can remind us that we can act and be otherwise—that the shortsighted self-interest that motivates, for instance, continued fossil fuel extraction is endemic to capitalism, not to our species, much less to life itself. We can find ways to live collaboratively with the bewildering array of life that roots and scurries across our planet, but only if we reckon with competition’s hold on our thinking—for if we see life as merely a competitive struggle to survive, we will make it one.
I’ve pondered why Favini has so badly misrepresented the history and content of evolutionary biology, and the only conclusion I can reach is that he’s a woke cultural anthropologist who is willing to distort the nature and history of science in the interest of promoting a socialist program. But he’s dead wrong in claiming that evolution is completely obsessed with competition (except between genes when you talk about natural selection), and equally wrong about the evolution of cooperation having been completely neglected until Lynn Margulis came along.
Since Favini is young, I won’t be too hard on him, except to advise him to drop this particular hobbyhorse, as it will only hurt what reputation he has. Or, rather, what reputation he has among evolutionists, as cultural anthropology is largely a miasma of nescience.
Several readers sent me this new video by Ze Frank, which is shorter than his other videos and also has unique music (Ze Frank wrote the music, too). I had no idea that ostriches mate this way, and it’s interesting to contemplate what the female is looking for here when she’s “choosing”. (I don’t think it’s “beauty”.)
Here’s the New York Times‘s list of the ten best books of 2019. You can find the 2018 list here and the 2017 list here. I couldn’t be arsed to go back farther.
There’s not a pure science book in the lot, though there’s a sort-of-science book on the Chernobyl disaster, which is more dramatic history than science, and in 2018, Michael Pollan’s excellent How to Change Your Mind, which is science related but also about personal experience, made the list.
Over the last three years, there have been thirty NYT “notable” books, half fiction and half nonfiction, with the latter including history, biography, sociology, and autobiography. But there’s only one pure science book, The Evolution of Beauty by Richard Prum; the Times‘s review of that is here. (By pure science book, I mean a book that is wholly about science, without big swaths of autobiography or other non-science stuff. That is, books like those by Richard Dawkins, Carl Sagan, and Stephen Jay Gould.)
Sadly, Prum’s book, while it has lively writing and some good bits, is deeply flawed—to the extent that its main message, that we now understand well how sexual selection works in animals, is wrong. (See my posts, which also summarize critical reviews from the scientific literature, here, here, and especially here as well as the review discussed therein.) The reviewer of Prum’s book, David Dobbs, who clearly isn’t up on sexual selection, simply bought Prum’s thesis whole hog, and didn’t mention any criticisms of the “runaway theory” so beloved by Prum and so problematic to evolutionary biologists. It’s not a thoughtful or well-informed review.
Regardless, 3% of all best books being science books over three years is a pitifully low figure, for there have been some very good science books or science-related books published since 2016. This paucity of science literature on awards lists, however, is typical, and shows that we’re still stuck in the Two Culture stage.
When one thinks of spectacular sexual displays, one thinks of the bowerbirds of Australia or New Guinea’s bird of paradise. But here’s one closer to home. This video, from The Center for Biological Diversity, shows the mating strut of the male American woodcock (Scolopax minor), a cute species that lives in Eastern North America.
This male American woodcock has some glide in his stride and some dip in his hip. Here he is performing an early morning “sky dance” to woo the woodcock ladies in springtime at Moosehorn National Wildlife Refuge in Maine.
Actually, this is only one part of a very complicated courtship. Wikipedia describes it all:
In Spring, males occupy individual singing grounds, openings near brushy cover from which they call and perform display flights at dawn and dusk, and if the light levels are high enough on moonlit nights. The male’s ground call is a short, buzzy peent. After sounding a series of ground calls, the male takes off and flies from 50 to 100 yards into the air. He descends, zigzagging and banking while singing a liquid, chirping song. This high spiralling flight produces a melodious twittering sound as air rushes through the male’s outer primary wing feathers.
Males may continue with their courtship flights for as many as four months running – sometimes continuing even after females have already hatched their broods and left the nest.
Females, known as hens, are attracted to the males’ displays. A hen will fly in and land on the ground near a singing male. The male courts the female by walking stiff-legged and with his wings stretched vertically, and by bobbing and bowing. A male may mate with several females. The male woodcock plays no role in selecting a nest site, incubating eggs, or rearing young. In the primary northern breeding range, the woodcock may be the earliest ground-nesting species to breed.
Of course I had to look this all up. The following two videos show the display flight with the twittering feather sound, and the second video shows the ground call, the “short, buzzy peent.”
Several species of animals, including damselflies, are known to remove sperm—presumably from previously-mating males—before they ejaculate their own sperm into a female. (Damselfly males have a “penis scoop” for this purpose; see photo at bottom.) This removal is a prime example of male-male competition, which is a form of sexual selection that doesn’t involve female preference.
It’s been known for a while that some species of nudibranchs, gorgeous marine molluscs that lack shells, also remove sperm with spiny penises during copulation. These species, also known as “sea slugs”, are simultaneous hermaphrodites, so when they copulate, each individual both donates sperm to its partner and receives sperm in its own female bits. (They do not fertilize themselves).
In a new paper in the Journal of Ethology (click on screenshot below to see the free paper, and get the pdf here), Ayami Skiezawa et al. did something new: they did DNA analysis on the removed sperm to see if it actually did come from males who mated previously. After all, it could be a male’s own sperm instead of sperm from a competitor.
But first, the system. The species studied was Chromodoris reticulata, a lovely nudibranch found in tropical and subtropical waters of the western Pacific Ocean. It’s shown in the first photo below, which also shows how nudibranchs, which means “naked gills” get their name. (All photos and their captions are from a 2013 article by Ed Yong in National Geographic.)
Here’s copulation between two individuals; you can see that each one insinuates a thin penis into the female organs of the other:
The penis is covered with backwards-pointing spines that are covered with entangled sperm after copulation. The odd bit about this species is that the penis is self-amputated (“autotomized”) about twenty minutes after mating, and it simply grows a new willy, ready for copulation within a day.
The new paper, below, went a step forward from the morphological observations in damselflies and in the earlier paper cited above: it did genetic analysis of the removed sperm.
It turns out that while earlier work showed clearly that penises like this one removed sperm after copulation, it wasn’t absolutely clear that this sperm was that of males who had mated previously. While such removal would clearly be advantageous, leading the remover to have more offspring than he (I’m referring to the male bits) would have had otherwise, the notion that this was what was happening was based on looking at the amount of sperm in the female parts before copulation versus after removal (presumably in these cases ejaculation was prevented). It would be better to actually look at the genes in the sperm itself to see if the nudibranch was removing sperm from other males.
And that’s what Sekizawa did, and that’s what they found. They put nudibranchs, captured off Okinawa, in tanks and then gave them each three successive mating partners over a series of days. Each partner’s genetic constitution was determined using six microsatellite markers (bits of DNA). And after each copulation, they removed the sperm mass adhering to the spiny penis and looked at the genes in that sperm. This is a simple idea, but it’s important to do this kind of analysis so you can see what’s really happening.
The results were crystal clear: in 36 sperm clumps taken from postcopulatory penises, 28 had genes from nudibranchs who had deposited sperm in the mating partner in an earlier mating. Indeed, in some individuals they found sperm that didn’t match any of the nudibranchs who had mated with the partner; this might have been from individuals who mated with the focal nudibranchs before they were taken from the wild. They also found some genes from the mating partner itself, probably from bits of tissue adhering to the spiny penis. And in some cases sperm from at least two previous mating partners was found.
This pretty much finalizes our understanding of this phenomenon, at least in this species of nudibranch. There’s little doubt of the selective advantage that accrues to an individual who removes sperm from a previous mating partner: you get more offspring than you would have had otherwise.
One question remains, though: why do these things self-amputate their penises after each mating? The authors suggest an answer (my emphasis):
C. reticulata autotomizes its penis after every copulation (Sekizawa et al. 2013) and it is thought that the autotomy of the penis evolved to remove allo-sperm from the mating partner efficiently. We clarified in this study that sperm donors removed allo-sperm already stored in the copulatory pouch(es) of sperm recipients with backward-pointing spines on the penis as the final process of their copulation. Though a long and thorny penis is advantageous in scraping out allo-sperm at copulation, such a penis is difficult to pull back into the body again after copulation. And the backward-pointing spines on the penis covered with sperm at copulation will not remove allo-sperm efficiently at the next copulation, like a VelcroTM tape. Such morphological and functional inconveniency may have made C. reticulata develop a cheap and fragile penis and dispose of it, rather than a robust but expensive one and reuse it.
Just for fun, here’s how damselflies do it. This figure, showing the damselfly penis with a glop of sperm, presumably from a male who mated to the female previously, is from a paper by Jon Waage. “sm” refers to the sperm mass adhering to the penis, also bearing backward-pointing spines. This spiny morphology and its function are remarkable examples of convergent evolution in two distantly related groups, insects and molluscs. This photo comes from Jon Waage’s Researchgate page; Waage, now a professor emeritus at Brown University, is the one who made this remarkable finding 35 years ago.
Here’s the latest Radiolab podcast, this time about sexual selection in birds and about Richard Prum’s revival of the idea of “runaway sexual selection,” which he calls the “beauty happens” theory. (It’s in his book, The Evolution of Beauty: How Darwin’s Forgotten Theory Shapes the Animal World—and Us.) I’ve written about Prum’s book before, and about my criticisms of his ideas—or rather, how he presents other people’s ideas—so I won’t go into that here.
I was interviewed by the Radiolab hosts last summer about sexual selection, but the show has just appeared today (click on screenshot below and then on the “listen” button to hear the 45-minute podcast). Note that the show claims to “present another way of looking at evolution.” One could construe “another way of looking at evolution” as simply the widely accepted view that sexual selection (rather than “survival of the fittest”) explains sexual dimorphism, or, alternatively, as Prum’s view that runaway sexual selection based on “random” female aesthetic preference is the best explanation for sexual dimorphism of color and behavior instead of “good genes” models positing that such traits indicate a male’s genetic quality.
When I talked to the hosts last summer, I got the idea that they had bought into Prum’s idea of runaway sexual selection as the best explanation of sexual selection, although, of course, there are other models, as described in the review of Prum’s book in Evolution by Gail Patricelli, Eileen Hebets, and Tamra Mendelson (if you’ve read Prum’s book, you must read that review).
It turns out that this show is not entirely—or even largely—about runaway sexual selection, though that process figures heavily in the last half. Much of the show is simply about the wonders of sexual selection and the traits it creates, and features interviews with scientists working on duck penises (the show begins with a discussion of that issue, which is of course a way to attract ears) and on bowerbirds (Patricelli), and it’s not bad.
The discussion of sexual selection and Prum’s “beauty happens” model begins about halfway in, with Prum calling evolutionists’ acceptance of “good genes” models, in which male traits indicate their genetic fitness, a “flattened, dumb down and ideologically purified version of Darwin’s actual richness.” Well, that’s grossly unfair, as all of us recognize that there are a variety of models for how sexual selection works, with Prum’s “runaway” model being just one of them. (Behavioral ecologists tend to concentrate more on good genes, though.)
But, as I said, there are more than just the runaway model and “good genes” models. There are, for instance, “sensory bias” models, in which female preference is not a random phenomenon that gives the female “aesthetic” preferences, but that such preferences themselves are a product of evolution. Female may prefer certain traits or behaviors of males because (as I say in the show), those preferences are either a byproduct of evolution on their sensory system, or a direct result of selection. (Females may be attuned to some sounds more than others, for instance, because those sounds give them useful information about their environment.) And if that’s the case, then there may be natural selection operating on female preference by itself.
And if female preferences are subject to this kind of selection, Prum’s “beauty happens” model runs into trouble, for it assumes there are no selective constraint on female preference. (This is taken up in the Patricelli et al. review). If such selection occurs, the runaway often doesn’t work.
Further complicating attempts to distinguish the models is the fact that they can work together. The paper below, for instance, shows that in many cases—at least according to theory—runaway sexual selection can create a situation in which females are also choosing males with good genes, so experiments to distinguish the runaway vs. the good-genes model for the origin of sexual selection would be hard or impossible. (Click on screenshot to go to the paper.)
When I talked to Krulwich et al. in our 90-minute conversation (they managed to insert in the podcast the noises of me sucking on a coughdrop before the interview began!), I had two aims:
1.) To point out that Prum’s “beauty happens” model was not NOT a “null model” of sexual selection that should be assumed to be true in the absence of other information. Further, I wanted to point out that there were problems with this model itself, as it makes assumptions that may not be true (i.e., that there’s no direct selection on female preference itself). While I think the runaway model is certainly plausible, and must have played some role in the evolution of male traits and female preferences, there are other plausible models as well.
2.) To point out that hard data on which model explains a given case of sexual selection are sorely lacking. It’s hard to distinguish the various models, especially because selection happened in the past and because the models can operate together. To assert, as Prum does, that we know one model explains nearly all sexual dimorphism for ornaments and calls, is to make an unwarranted claim. It’s not that we know Prum is wrong; it’s that we don’t know much about how any of these systems evolved.
How did I do? Well, my bit begins at about 35:30; you tell me. I was surprised that the show let some of my more critical remarks about the book appear. But I think it’s good that the public knows how scientists can disagree on matters where there is no dispositive data.
In the end, Krulwich goes into a soliloquy in which he seems disappointed that we don’t know the answer, and almost depressed because future research may show that different models may explain different cases of sexual dimorphism. This would mean that we don’t have a “rule” for how sexual selection works, but a series of anecdotes that give us statements about the relative frequencies of different processes.
So be it: this is evolution, not physics, and evolution works in multifarious ways. I had a few pithy statements about this issue in my phone interview, but, sadly, these didn’t make it onto the show.
As a whole, I’m not sure how well the show hangs together. I can’t listen to it as if I were a nonscientist hearing about this for the first time, so give your take below. I think the Radiolab folks will be reading this, so be civil but also be honest.
With the publication of his book The Evolution of Beauty (subtitle: How Darwin’s Forgotten Theory of Mate Choice Shapes the Animal World—and Us), Yale ornithologist Richard Prum gained an extraordinary amount of publicity in the popular press. His theme was that “beauty”—that is, the evolution of extreme and stunning displays and ornamentation in male birds—results from a form of “runaway sexual selection” in which females’ random preference for extreme male traits produces amazing sexual dimorphism that has nothing to do with natural selection. (The peacock is perhaps the most famous example.) Prum’s book got two separate reviews in the New York Times, at least one other notice, and two big reportorial pieces, including recent the one below. The book was also nominated for a Pulitzer Prize for nonfiction, though it didn’t win.
Prum’s book is worth reading for two reasons. First, it presents a strong defense of the “runaway” model of sexual selection Prum calls it the “beauty happens” model, in which random female preferences lead to the exaggeration of male traits up to the point at which those traits actually hurt the male’s reproductive success (a peacock with a bigger tail would presumably not only be unable to fly, but would be a target for predators and find it hard to get around). Second some of Prum’s writing is very good, and his examples of exaggerated male behaviors and plumage engrossing and yet unknown to many laypeople.
But the book, as I’ve written before (see posts here), is tendentious. It ignores other models of sexual selection (except to denigrate them), it ignores the weaknesses of his own favored runaway model, and it misrepresents the views of evolutionary biologists (many of whom agree that the runaway may be important, but won’t buy into Prum’s view that it’s ubiquitous). Prum claims that the runaway model is universally rejected by biologists in favor of “good genes” models (male traits indicate their genetic endowment). But that claim isn’t true: we just don’t have much data to distinguish all the competing models we have for how sexual selection works.
Further, Prum ties his model to progressive politics, saying that female choice in animals should hearten us because it shows that female “sexual autonomy” is natural. But such autonomy isn’t always present: many animals, for instance, have forced copulation. Bedbugs, for example, exhibit “traumatic insemination”, in which males bypass copulation by simply injecting sperm through the female body wall, with that sperm finding its way to the female eggs. Females don’t get to choose their mates, and copulation can actually kill them.
And there are many cases of forced and unwanted copulation by males, as well as male-male competition (viz., elephant seals) in which females are simply constrained to mate with whichever male wins a contest. Prum’s evocation of politics therefore demonstrates the “naturalistic fallacy”: that what happens in nature is what we should emulate. However, a lot of what happens in nature is stuff we shouldn’t emulate.
Prum also ties other models of sexual selection, including those in which a male’s traits indicate his vigor, health, or presence of “good genes”, to eugenics, and Nazi genocide, tarring the theories he doesn’t like with the social-justice cry of “Nazi”. This is unconscionable. I can’t help but think, though, that Prum’s tying sexual selection to feminism was partly responsible for the book’s popularity and its Pulitzer nomination.
As I’ve written before, however, while Prum’s book received public approbation and good reviews—mostly from reviewers with no science background)—the reaction of the scientific community itself has been tepid and mostly critical for reasons I gave above. The three reviews I’ve read in scientific journals, including one by Gerald Borgia and Gregory Ball and another by Doug Futuyma, both highlight serious problem’s with Prum’s presentation, including the ignoring of alternative theories, the misrepresentation of the “beauty happens theory”, and the unwarranted connection between women’s rights and mate choice in birds. A more recent and much longer review, by Patricelli, Hebets, and Mendelson, published in Evolution (click on screenshot below for free access), was severely critical, and rightly so, though the authors did their best to be evenhanded and polite:
I’ve discussed this review before (full disclosure: I gave the authors some suggestions on a draft of their piece), and so won’t go over its contentions here. But if you want to read a review of Prum’s book—and one that is objective but critical—Patricelli et al. is the one to read. It is a good palliative for the publicity Prum gets repeatedly about his book.
That aside, several readers sent me the link to Ferris Jabr’s NYT piece above, suggesting that I write about it. I intended to, but was in Hawaii where I was having too much fun to work. Now that I’m back, I’ll summarize it as briefly as I can. (The piece is very long, and appeared in the NYT Sunday Magazine, an indication of how important the editors deemed the topic.)
The good bit is that Jabr at least indicates, as many writers haven’t, that the scientific community is lukewarm about The Evolution of Beauty and that Prum is somewhat dogmatic and dismissive of his critics. For example:
Despite his recent Pulitzer nomination, Prum still stings from the perceived scorn of his academic peers. But after speaking with numerous researchers in the field of sexual selection, I learned that all of Prum’s peers are well aware of his work and that many already accept some of the core tenets of his argument: namely that natural and sexual selection are distinct processes and that, in at least some cases, beauty reveals nothing about an individual’s health or vigor. At the same time, nearly every researcher I spoke to said that Prum inflates the importance of arbitrary preferences and Fisherian selection to the point of eclipsing all other possibilities. In conversation, Prum’s brilliance is obvious, but he has a tendency to be dogmatic, sometimes interrupting to dismiss an argument that does not agree with his own. Although he admits that certain forms of beauty may be linked to survival advantages, he does not seem particularly interested in engaging with the considerable research on this topic. When I asked him which studies he thought offered the strongest support of “good genes” and other benefits, he paused for a while before finally responding that it was not his job to review the literature.
Of course it was Prum’s job to review the literature, and especially to weigh his favored theory against alternatives, including “good genes” models and “sensory bias” models, in which female preference are not random but the byproduct of natural selection based on the species’ environment. How could it not be an author’s duty, when defending a theory, to review the literature for and against that theory?
Jabr also says this:
Like Darwin, Prum is so enchanted by the outcomes of aesthetic preferences that he mostly ignores their origins. Toward the end of our bird walk at Hammonasset Beach State Park, we got to talking about club-winged manakins. I asked him about their evolutionary history. Prum thinks that long ago, an earlier version of the bird’s courtship dance incidentally produced a feathery susurration. Over time, this sound became highly attractive to females, which pressured males to evolve adaptations that made their rustling feathers louder and more noticeable, culminating in a quick-winged strumming. But why, I asked Prum, would females be attracted to those particular sounds in the first place?
To Prum, it was a question without an answer — and thus a question not worth contemplating. “Not everything,” he said, “has this explicit causal explanation.”
Here Prum simply dismisses something that scientific reviewers mentioned repeatedly—where do female preferences come from? Prum assumes they are random, but there is a thriving field of sexual selection studying female preferences, showing how they might result from natural selection instead of just being “random” (i.e., aspects of neuronal wiring that have nothing to do with natural selection for the preference). Jabr also says, properly, that not all biologists have dismissed the runaway model, as Prum contends they have, but see it as one of a competing panoply of models that are hard to resolve. (Getting this kind of data from nature or even the lab is very difficult, and we weren’t there to see how sexual selection operated in the past.)
But in the rest of the article, Jabr seems to buy a lot of Prum’s contentions without properly evaluating the criticisms of other scientists. For example:
1.) The runaway model is not “Prum’s theory.” This model was first suggested by Ronald Fisher and elaborated and developed by scientists like Russ Lande and Mark Kirkpatrick. Yet Jabr repeatedly refers to the “beauty happens” model as “Prum’s theory”, as when he says that “Prum’s indifference to the ultimate source of aesthetic taste leaves a conspicuous gap in his grand theory.” (That statement is correct except that it’s not Prum’s grand theory.) This misleading attribution of the theory happens repeatedly. Let us be clear: Prum’s book is about presenting, defending, and applying a theory developed by other scientists.
2.)Jabr buys into Prum’s contention that sexual selection is fundamentally different from natural selection. Most biologists, I think, would disagree, seeing sexual selection as a subset of natural selection. That is, sexual selection is a form of selection based on female mate choice rather than other factors. But both sexual and natural selection involve enhancing those traits that affect reproductive success. (Jabr seems to mistake natural selection as a form of selection that enhances survival rather than reproductive success, but in fact the currency of all selection is the number of offspring that survive to spread your genes.). This may seem a semantic question, but both Jabr and Prum use this distinction to suggest that the runaway theory is a big and revolutionary improvement over previous notions of natural selection. This further inflates the runaway theory into something that it’s not.
In fact, natural and sexual selection blend into each other, and in some cases you can’t distinguish them. If a male produces sperm that swim faster than the sperm of other males in his species, and thus he gets more offspring, is this natural or sexual selection? It’s not based on mate choice, but does involve reproductive success. This is a form of male/male competition, analogous to those bull elk who butt horns during mating season, with the winner getting a harem of females. No female choice is involved in either case, but both could be seen as sexual selection. But they also represent natural selection—selection based on some individuals having traits (horns, fighting ability) that enables them to leave more genes. My own judgment is that sexual selection is simply a subset of natural selection that involves mate choice, and not something fundamentally different.
3.) Jabr leaves out some aspects of Prum’s views that scientific critics have homed in on. Jabr doesn’t mention, for example, that Prum views the runaway model as the “null model” of sexual selection. That is, Prum deems it the model that we should accept unless we have good evidence for other models. But the runaway model isn’t null in that way: it does carry its own assumptions that themselves have to be justified and tested, such as female preference being “random” and not itself initially the result of natural selection or subject to stabilizing selection. The runaway assumes that male traits and female preferences are genetically correlated, and so on. No single model of sexual selection can be regarded as a “null model” to be regarded as a default option in the absence of any evidence.
4.)Jabr doesn’t fairly summarize the extent of scientific criticism of Prum’s book. While he does cite Borgia and Ball’s criticism, he neglects those of Futuyma and especially the thorough paper of Patricelli et al., and thus leaves out some important problems with Prum’s views (see below). Further, Jabr seems to have consulted critics at only the University of Texas at Austin, including my colleagues and friends Gil Rosenthal, Molly Cummings, and Mike Ryan. These people generally work on the sensory bias model of sexual selection, and thus emphasize theories different from Prum’s, but it would have been good to consult others who work on Prum’s model itself. These would include both Mark Kirkpatrick (also UT Austin!) and Russ Lande. I have talked to several “runaway” modelers, and their take is different from Prum’s: while they think the theory can operate, they are wary of its ubiquity in the absence of empirical evidence. This view, by the very proponents of Prum’s favorite model, shows a scientific caution far more admirable than Prum’s dogmatism.
5.) Jabr doesn’t mention at all an important aspect of Prum’s book: Prum’s view that because in some species females have “sexual autonomy” in choosing males, that hearten feminists who, rightfully, are against sexual coercion by human males. This omission by Jabr is a mistake, for this part of Prum’s message is one of its selling points, and surely explains some of the book’s popularity. But we shouldn’t buttress our morals by looking for parallels in nature, for, as I’ve said repeatedly, doing that makes our morality subject to revision via new information about nature. While some moral judgement can depend on empirical information (abortion may be one example), arguments about human rights and autonomy should be independent of how other species behave.
Jabr further ignores Prum’s invidious use of eugenics and comparisons to Nazis and genocide to tar models of sexual selection based on “good genes”. Ball and Borgia explicitly mention this, as do Patricelli et al. in the section of their review called “Birds and bedbugs make bad politics” (all three authors of that review are women).
My view then, is that Jabr’s summary of Prum’s work and the “beauty happens” theory is better than that of any of the summaries in popular venues, but still suffers from a general laziness manifested in contacting only scientists at UT Austin and in failing to summarize much of the criticism leveled by scientists at The Evolution of Beauty. Jabr didn’t do his scientific homework. The definitive popular critique of Prums’s views, as opposed to those that have already appeared in scientific journals, has yet to be written.
Buffleheads (Bucephala albeola) are cute diving sea ducks that have a pronounced sexual dimorphism, especially in the breeding season. Here are the males vs. females from the Cornell bird site. This will help you pick out the sexes in the video below.
The video shows a group of bufflehead males trying to impress a few females. Note that the male display includes a lot of elements that demonstrate vigor, like head-bobbing, wing-flapping, and racing (in one case a female appears to incite a male to race). It’s hard to avoid thinking that females are looking for the most vigorous males, because those males have fewer parasites to transfer during mating (males have no parental care in this species), because the males have “good genes” that can be passed onto offspring, or a combination of these “direct” and “indirect” benefits.
But if female choice is basically random, as Richard Prum suggests, and has nothing to do with the genetic composition of the male, why are the most vigorous males always the ones who win? I suppose you cold say that they’re simply more conspicuous, but I don’t think so. These males are showing off a lot of different aspects of vigor, and the females are watching them closely before making their choice.