Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
This short video, about evolution in real time, is the best yet in the sequence of the “Twelve Days of Evolution” videos, produced by PBS and “It’s Okay to be Smart. ” I’ll be presenting, reviewing, and annotating these over the holidays:
The creationist canard dispelled here is the idea that if we can’t see evolution in real time, it doesn’t happen. (Never mind that the fossil record gives us tons of evidence for the process.) The example it gives is a nice one: the work of Marlene Zuk and her colleagues (she occasionally comments here) on the loss of sound-producing structures in crickets. You can read about it in detail at this site, but the upshot is that the invasion of a cricket-parasitizing fly in two Hawaiian Islands imposed strong selection on the resident crickets to lose their song, for the fly uses that song to detect its prey. Not only was evolution extremely fast in this case, but it involved only a single mutation on the X chromosome, one that ablated the stridulation combs of males. Soundless males survived, for the survival advantage more than outweighed their loss of ability to attract females through singing.
The example is not just evidence for evolution, but evolution via natural selection. Remember that there are other causes for evolution besides natural selection, most notably genetic drift.
But of course we’ve had examples of natural selection in real time for ages. John Endler’s book Natural Selection in the Wildgives several hundred, all from nature, and we’ve known about microbes evolving resistance to antibiotics for decades. Ditto for plants evolving resistance to herbicides, insects to insecticides, and plants to heavy metals brought to the surface by mining.
And most of you have heard of Peter and Rosemary Grant’s work on selection in the medium ground finch (Geospiza fortis), one of the best-documented examples of natural selection in vertebrates. A drought killed off small plants on the Galápagos island of Daphne Major, enabling only those individuals with larger beaks, who could crack the remaining big seeds, to survive. The population’s beak size increased by 10% in one generation, and the genetic and ecological basis of the trait change is well understood.
Section 5 of Douglas Theobald’s magnificent evidence-for-evolution website, 29+ Evidences for Macroevolution, gives other examples, though I can’t seem to access it now.
I frequently teach evolutionary biology in the spring semester, but for various reasons I will not be teaching it this coming spring. A few days ago, a student who wanted to take the course, but now couldn’t, asked what he could read in lieu of taking it. We discussed some suggestions, and then I sent him a copy of a chapter on “The evidence for evolution” that I’d written for The Princeton Guide to Evolution, edited by my friend and colleague Jon Losos. The point was not for him to read the chapter (although there’s nothing wrong with doing that!), but rather to send him the list of “Further Reading” that closed the chapter. The Guide is intended for students, and for scientists reading outside their specialties, so the recommended readings are not at a highly technical level, but can be edifying for any curious and interested reader. We were limited to ten, and here’s what I chose.
Young, D. 2007. The Discovery of Evolution. 2nd ed. Cambridge: Cambridge University Press. Though last alphabetically, I list this one first, because it is a truly excellent book that is not well enough known (though I’m trying!) Ostensibly a history of evolutionary biology, it serves as a text for evolutionary biology itself, because it introduces and explicates not just the ideas and historical figures, but the evidence on which the major discoveries of evolutionary biology are based. It is intended for a general audience, and richly illustrated.
Carroll, R. 2009. The Rise of Amphibians: 365 Million Years of Evolution. Baltimore: John Hopkins University Press. This book, by the dean of North American paleontology, is a bit more technical, and includes accounts of the origins of vertebrates and reptiles, as well as of the origin of amphibians.
Dawkins, R. 2009. The Greatest Show on Earth. New York: Free Press. Another account of the evidence for evolution for a general audience, by another person we all know.
Futuyma, D. J. 2013. Evolution. 3rd ed. Sunderland, MA: Sinauer. This is the leading undergraduate textbook of evolutionary biology, and is a good read for biology majors. It would require a bit more effort from a general reader, but it’s chock full of good stuff and worth the effort. Doug’s 1997 Evolutionary Biology (Sinauer) is more of a graduate level text, and, though a bit dated in spots, is more comprehensive and still quite worthwhile.
Grant, P. R., and Grant, B. R. 2008. How and Why Species Multiply: The Radiation of Darwin’s Finches. Princeton, NJ: Princeton University Press. The Grants have published a number of more technical books on their groundbreaking work in the Galapagos on Darwin’s finches, but this volume provides a more accessible overview of the detailed evolutionary studies they and their associates have conducted over four decades, including several episodes of closely observed evolutionary changes. They have recently published a more technical but still readable account, including several more years of field work, in 40 Years of Evolution (2014, Princeton University Press).
Mayr, E. 2001. What Evolution Is. New York: Basic Books. A summary of the evidence for evolution and its causes by the man Jerry has rightly called the “Darwin of the 20th century.”
Prothero, D. R. 2007. Evolution: What the Fossils Say and Why It Matters. New York: Columbia University Press. Intended for a general audience, this richly illustrated account of the fossil record emphasizes transitions between major groups, and is a great resource for understanding the broad outlines of evolutionary history and how we know how it happened.
Shubin, N. 2008. Your Inner Fish. New York: Pantheon Books. Another book by someone we all know, this is a popular account of the discovery of the fish-amphibian transitional form Tiktaalik, and of the traces of common ancestry in the anatomy and genes of vertebrates and other animals.
My tenth book was Darwin’s Origin of Species, but since almost every chapter could have cited it, and chapters before mine already had done so, it was left out. But I can add it back in here for WEIT readers.
Darwin, C. 1859. On the Origin of Species. London: John Murray. The modern reprinting which I read and usually cite from is the Harvard University Press reprint of 1964, with an introduction by Ernst Mayr. Although I have heard that some find Darwin’s “Victorian” style offputting (what do they want?– he was a Victorian), I find it quite readable, and still remarkably cogent and astute.
I can also add in here for WEIT readers the Princeton Guide, for which I prepared the original list. It has dozens of chapters by a top selection of evolutionary biologists (present company excluded!).
I would also add in a second evolution textbook, coauthored by the accomplished science writer Carl Zimmer, and by the scion of a distinguished biological family, Doug Emlen.
Zimmer, C., and D.J. Emlen. 2016. Evolution: Making Sense of Life. 2nd ed. Greenwood Village, Colorado: Roberts. Well written and well illustrated; at a slightly lower level than Futuyma (Z&E is sort of for sophomores, Futuyma for seniors; juniors could go either way). A great book for someone teaching an evolution course– very clear and well structured, with a variety of useful teaching aids.
Several years ago, Jerry prepared a list of the five books about evolution for general readers that he would pick. I did not consult Jerry’s list when I prepared mine for the Princeton Guide, so the comparison is of interest. The only one on both lists is Prothero. Jerry also chose the Origin (which would have been on my list if it had not already been recommended in the Guide); Dawkins’ Blind Watchmaker, which I too highly recommend; Janet Browne’s two volume biography of Darwin, which I again highly prize and recommend as well (although if you’ve only one history book to read, read Young’s Discovery of Evolution); and two books by Steven Jay Gould: an essay collection, and The Mismeasure of Man (they let Jerry pick 6 books). In comparing our lists, do recall the differences in the audiences for our lists– Jerry’s intended audience being nonscientist readers, mine being a bit of a hybrid, but leaning toward science students.
In teaching our undergraduate evolution classes, Jerry and I have both, at least at times, used Futuyma’s textbook and the Origin as our required readings. Although he and I have consulted occasionally on our teaching of evolution, I believe we arrived at our choices of books independently.
NOTE: The Princeton books (Losos, the Grants) are on a 30% off sale till November 15th– buy now!
[The internet is down at the Kirksville Holiday Inn. The only other time this has happened to me was when I was in Russia. What this means is that posting may be light today. Fortunately Greg prepared a post on a recent talk he gave about evolution, which is below. JAC]
by Greg Mayer
Jerry has posted a couple of times in the last week or so on the “creationist shenanigans” at Georgia Southern University, where a professor is apparently openly proselytizing for his religion in classes on the history of science. One of the items the professor has produced is an online document titled “No evidence for evolution“. It’s actually a rather sad document– and not just because it’s a typically dishonest creationist exercise in quote-mining, which would have us believe that Jerry Coyne, George Gaylord Simpson, Jeff Levinton, Niles Eldredge, and Steve Gould, among others, can all be rallied to the cause of creationism. Nor is it because he mixes in quotes from the likes of Michael Denton and Francis Hitching, as though they had any authority at all. Nor is it even because of his schizophrenic view of Gould and Eldredge, who on the one hand he wields in support of creationism, but on the other he attacks (through quotes) because (gasp!) they are evolutionary paleontologists. No, it’s sad because it’s all so old. Other creationists did this decades ago– and, frankly, better. The quotes are almost all old ones– from the 1980’s and earlier (the latest quote I noted was 1997– the page is dated 2002). The reason it’s so sad is that not only does this guy know nothing about biology or paleontology, he’s not even a very good creationist– he apparently hasn’t kept up with developments in his own “discipline”!
Just a day or two after Jerry posted, my colleague Chris Noto informed me that a talk I had given at Darwin Day celebrations earlier this year was now available online. Entitled “The Evidence for Evolution”, it seemed like a happy coincidence, and so I share it with you here. (Note that the Parasaurolophus and sauropod behind me seem quite interested, the latter even bending his neck above and around me so he can read my notes on the podium! There was a human audience too, although, as usual, until a late attendee arrived, no one wanted to sit in the front seats.)
The talk was given at the Dinosaur Discovery Museum in Kenosha, Wisconsin, as part of their Darwin Day events last February. It was based on the chapter I wrote for The Princeton Guide to Evolution, edited by my friend and colleague Jon Losos, which was officially published right about the time I gave the talk. The talk is about descent with modification per se, and not on the mechanisms of evolution (except insofar as the observation of current evolutionary changes allows us to see such mechanisms directly), and the main topics were the fossil record; transitional forms; comparative morphology, embryology and genetics; biogeography; and evolution in action. I would particularly draw attention to the example of observed speciation in Spartina in England (about 30:44). It’s an example of allopolyloid speciation (a new species arises by hybdidization with increase in the number of chromosome sets), which is common in plants (though not animals), and is expected to occur very rapidly, but it’s nice to have a case where humans observed the speciation event start to finish (1829-1892).
(The camera battery went dead for a bit, so there’s about 5 minutes of the biogeography section missing; the dead space was edited out with a “wave”– you’ll notice it.)
Mayer, G.C. 2014. The evidence for evolution. pp. 28-39 in J.B. Losos, ed., The Princeton Guide to Evolution, Princeton University Press, Princeton, New Jersey.
This video came out only five days ago and already has garnered 127,000+ views, so the production outfit, Stated Clearly, must be doing something right. And indeed, it’s very good. If you can’t get somebody to read WEIT, at least have them watch this video, and ask them, if they’re creationists, how their own theory could explain the evidence shown. First watch the video, which I like, and then I’ll tender a few comments:
By concentrating on cetaceans (whales, dolphins, and their relatives), the film is able to go into depth about one evolutionary transition, and it does it well, especially because several whale experts (Thewissen and Gingerich in particular) generously gave their advice. I liked the pictures of the vestigial whale “pelvis” with the ball-and-socket still there, and the intermediate form showing a skull with the nostrils moved halfway up toward the crown of the head.
A few quibbles: first, the video characterizes the theory of evolution as having two main tenets: 1. The common ancestry of all life, and 2. The fact that evolution was a product of purely natural processes. These are correct, but they should have said more. For instance, all science rests on the assumption (amply verified) of naturalism, so that is not unique to evolution, though important for the many (31% of Americans) who think evolution is God-guided.
More important, they should have added that there is EVOLUTION WITHIN LINEAGES: that is, lineages not only ramify, but each lineage can itself evolve. That’s implied but not stated explicitly. They missed evolution itself! In fact, if the group of whales they show do have an ancestor-descendant relationship, then they’re actually showing this within-lineage change.
At any rate, my own characterization of evolution would, as I say in WEIT, involve these tenets: 1. Evolutionary changes occur within lineages and these changes are populational rather than transformational: that is, evolution occurs by gradual generation-by-generation turnover of the genetic constitution of a population, not by changes of the individuals themselves; 2. Lineages splitting, or speciate. This produces the branching “tree of life.”. 3. This splitting of lineages, taken together with the evidence that all modern species stem from a single common ancestor that lived billions of years ago, means that every pair of species has a common ancestor somewhere in the tree of life. (The film says this, but should have added that the splitting itself is what gives rise to common ancestry.) 4. Gradualism: evolution usually takes a long time. It can be quick, happening in only a few generations, but major changes, such as the transformation of ancestral reptiles into birds, take hundreds of thousands to millions of years. Complex features like eyes and new groups like birds do not evolve overnight. 5. Much of the evolutionary process, and virtually all of the change that adapts animals and plants to their environments, occurs by natural selection, although there are other processes, like genetic drift, that can cause evolution. And yes, all evolutionary change occurs by natural, unguided processes: genes differentially proliferating due to either random chance (drift) or differential, repeatable ability to leave more copies than other forms of genes (natural selection).
In other words, my own characterization of evolution would have more than two features, and naturalism is assumed in all of them.
In terms of the evidence, I wouldn’t concentrate so much on homology of either genes or features as evidence for evolution. It is consistent with evolution, but it’s also consistent with God having given animals a similar Bauplan, with similar species having similar Baupläne. While the fact that bats have fingers in their wings is consistent with evolution, you could, at a stretch, say that’s consistent with God’s economical way of designing mammals. This is why I don’t use homology in my book as strong evidence for evolution. Creationists have an alternative explanation that sounds credible, at least to an uninformed layperson.
What does constitute strong evidence for evolution is the similarity, among organisms deemed related from functional gene similarity, morphology, and fossils, of nonfunctional DNA. If homology merely reflected God’s design, it would be hard to understand why God also made the nonfunctional bits of DNA more similar among species appearing more similar in both morphology and the functional bits of DNA. Related to that is the observation that presumed insertions of viruses that are now inactive occur at similar positions in “related” species, like chimps and humans. Again, those are the remnants of ancient infections in common ancestors, and it would be odd indeed if God had a hand in putting useless, inactivated viral DNA in exactly the same genomic position in close relatives. Since we now have good evidence that nonfunctional DNA changes in proportion to the time elapsed (via genetic drift), the similarity of such DNA among species gives an index of their evolutionary relatedness. And that relatedness happens to match the relatedness discerned on other grounds: vestigial organs, fossils, functional DNA, morphological homology, and so on. This coincidence of different indices of relatedness constitutes strong evidence for evolution.
The filmmakers’ use of embryology, vestigial organs, and the fossil record (a good record for cetaceans) was very convincing; these things do constitute strong evidence for evolution in that there is no quasi-credible creationist alternative—as there is for homology. I would have added two things, though these probably aren’t easy to find for whales. First, biogeoraphy—the distribution of plants and animals on Earth—is also strong evidence for evolution. The proliferation of life on oceanic islands (with some forms absent or nearly so, like mammals, amphibians, and reptiles) is one example. Biogeographic evidence for evolution is probably hard to find for cetaceans. I appreciate that you can’t cover all creatures in a short video, and it was clever to use only cetaceans, which have such a great fossil record, but by so doing the filmmakers missed out on biogeography, some of the most powerful evidence for evolution.
Second, “bad design” that makes sense under evolution but not under creationism is another good line of evidence for evolution. I can’t think offhand of “bad design” characters in whales, although I suppose the vestigial pelvis and legs could qualify as that, though to me they fall under the “vestigial trait” evidence. The authors might have added, in this category, the presence of vestigial olfactory receptor genes—”dead genes”—in cetaceans: the genes that enabled their ancestors to detect airborne odors. As I recall, dolphins have hundreds of such receptors, but every one has been rendered inactive by mutations, for cetaceans don’t use the same way of smelling as do their landlubber relatives. Ergo, the “air-sniffing” genes have become inactive. But they still lie fallow in the cetacean genome: useless remnants that testify to the group’s terrestrial origin. The DNA of many species is surely a graveyard of dead genes that testify to the truth of evolution. There is no alternative creationist explanation.
I have a bunch of photos from reader Stephen Barnard of Idaho, but he has sent a largesse of red-tailed hawks (Buteo jamaicensis). So here’s a special post with those photos, one of which provides a lesson about evolution.
I can’t resist pointing out that humans carry the vestigial remnant of a nictitating membrane from our ancestors in the form of the plica semilunaris in the corner of the eye (full nictitating membranes are absent in nearly all mammals except monotremes and marsupials). Go look at your plica semilunaris in the mirror now! Spread your eye as in the diagram and look in the corner by the nose. That’s the remnant of the nictitating membrane that your reptilian ancestors had. (Some of you who are less evolved* will have a more pronounced remnant.)
Here’s a photo of what to look for:
The hawk with the membrane retracted:
*only kidding, but I like to joke about that with the students
