Jerry Coyne: "The theory of evolution has been confirmed as true over and over"

by Felipe Nogueira

Interview with Jerry Coyne

Jerry Coyne is an evolutionary biologist, Professor in the Department of Ecology and Evolution at the University of Chicago. He is also a member of the Committee on Genetics and the Committee of Evolutionary Biology. 

Coyne is a big popularizer of evolution and science. His lastest book is Why Evolution is True, where he shows with clarity the several evidence supporting the theory of evolution and debunks many creationists arguments. 

I did an interview with him that is available on Youtube. This is the first part of the interview. I think having this post, the part of the interview we talked about several things about evolution (misconceptions, evidence, mechanisms), published today it's a good way of celebrating Darwin Day. I thank Jerry Coyne for his attention and kindness.  

Links: second part | video on Youtbe | versão em português

Can you explain why evolution is not just a theory?

It’s a theory and a fact. As I explain in my book, theory in science has a different meaning from what most people think of. I think that was used in debate between Ken Ham and Bill Nye. Someone in the audience said evolution is just a theory, implying it is just a guess or speculation. In science, a theory is a proposition or an explanation that purports to draw together a number of facts to explain a phenomenon. So, we have the theory of gravity, the germ theory of disease, for example. Or the atomic theory: matter is made by constituents called atoms. Atoms are facts. In the same way, evolution is called a theory, because Darwin proposed explanatory mechanism for all these diverse facts. So, evolution like the atomic theory or the germ theory of disease is both a theory and a fact at the same time, but a theory in scientific sense, which is a well-established explanation for a diverse group of phenomena. And again this is probably the most perverse misconception about evolution, at least in America.

I think you already answered my second question. You mentioned very clearly on your book that the theory of evolution is not just the statement the evolution had happened; it includes explanations why and how evolution happens. 

It’s the statement of what has happened and why has happened. [The paleontologist] Stephen Gould made that pretty clear, although he thought that a theory was the explanation why and the fact was the thing itself. It’s a matter of taste how you called a theory, but it’s not a matter of taste that theory of evolution is something that has been confirmed as true over and over again, and that what is important to emphasize when you came up with this misconception.

But the words “theory of evolution” are equivalent to “modern evolutionary synthesis”? 

The theory of evolution that I talked about in my book is the one most people hold, pretty much the one Darwin proposed, which involves elements of evolution, gradual transformation of population (genetically, although Darwin didn’t know genetics), splitting of lineages, so you get one species forming more, so you have a branch tree of life, and that gives the result that any pair of species has a common ancestor and that the organisms look like they are designed, which is the result of natural selection. So that is a Darwinian theory of evolution. Neo-Darwinian theory is based on genes and there is other process like genetic drift and horizontal gene transfer. They are important, and they have been confirmed as true, but for the average person who disbeliefs evolution, what they are disbelieving is those five propositions I just outlined. 

What do you think is the most common misconception about evolution? 

One is that is very common in children involves instantaneous transformation of population, like every individual turns into something else rather than a gradual genetic change in the composition of the population. Another one is that there is not much evidence for it, that we don’t have the evidence for one type of animal turning into another over time. But the fact is there are lot of evidence, people just don’t know about.  

One of the misconceptions is that evolution is just a random process. 

That’s a good one: “how all this can happened by chance?” Is easily dispelled if you understand what natural selection is, but it is very common. And in America it's connected with all kinds of religious things, like if you believe in evolution, you have to give up of your morality. That’s probably the main reason why religious people oppose evolution in America, and maybe Brazil as well, because it is religious country. They say "what basis do you have to be moral, if you are just an evolved animal, like a chimpanzee?" And that’s a misconception as well that comes from a misunderstanding of where morality really comes from. 

And there is the misconception of the definition of the word random in the context of random mutations.  

The average person is not sophisticated enough to know that mutation is a random process and less of them know what we really mean by random process, which is the occurrence of mutation is indifferent of its effects on the reproductive outcome of its carriers. That is probably most common among more sophisticated creationists. I don’t think it’s a misconception, I think it’s deliberate, it's something they say to make people question evolution, which is their mission  

There is also the misconception of “the missing link”; it’s not just one missing link, it’s a lot of them.  

That is a misconception of what a missing link really is. The missing link between human and chimps would be the common ancestor between human and chimps. That is a single species that split into the two populations: one which gave rise to hominids and the other gave rise to bonobos and the chimps. We generally not going to find a single species in the fossil record, but you don’t need the missing link to prove human and chimps have a common ancestor. You need, as I tell in my book, is if you go back earlier and earlier in the human lineage you would expect to find more and more transitional forms that show ape-like ancestor and, in fact, that’s what you find.  Ken Ham said the same statement in the debate last night: “we have evolution within kinds: dogs evolve into other dogs, but we never see a dog evolving into a cat”. But if you look in the fossil record, you see these transitions: Tiktaalik, which Bill Nye mentioned, is a transitional form between fish and amphibians; we have between amphibians and reptiles; the reptiles and mammals, the so called “mammal-like reptiles”. I mean, there is a very good fossil record there. We have between reptiles and birds, what a great collection of transitional forms we have on the feathered dinosaurs; between whales and theirs terrestrial ancestors, and of course all the transitions in the human lineage. We have not only the links between major types of animals that were predicted by the theory of evolution and there also the links between the so-called different kinds the biblical creation says could not exist. Those kinds of fossils absolutely dispelled any kind of creationism.

What about those creationists/intelligent design proponents’ ideas that the wing or the eye is too complex to appear by gradual changes over time?

Darwin was the first one to deal with the eye in The Origin, showing we have all degrees of eye development in living species and there is no problem envisioning how you go from one to another. Secondly, we have this paper by Nilsson and Pelger in Proceedings of The Royal Society*. They made a simple model of the evolution of a complex camera eye from a light sensitivity eye spot, like you have in plenary worms. They made very conservative assumptions about what mutations rates might be, about what the selection pressures are, and in few thousands generations they saw this eye spot evolve into a complex eye. So, we have two kinds of evidence that dispel the idea the eye is too complex to evolve. We have a sequence of eyes in living creatures which you can plausibly connect, showing how they can straight up. Second, we can make the process happen through computer simulation using conservative assumptions. And that goes to every other complex feature; the blood clotting is another one that intelligent design people use. They say “how can you get this complex cascade of enzymes reactions that results in a blood clot? It can’t possible evolve, because, if take out any intermediate step, the blood won’t clot. So, all got to be there and God did it”. But research show you can knock-out certain intermediate steps and still get clot. We don’t know how it happened, because we weren’t there, but you don’t need to actually observe it to reject creationists arguments that it is too complex to evolve. All you have to show is that you make a plausible scenario, where each step has adaptive advantage to show that evolution was plausible. And we have done that for almost all these traits that is supposedly non-evolvable and too complex.

Richard Dawkins’ The Selfish Gene focus on the gene centered view of evolution. But I think the evolutionary biologist Ernst Mayr was a critique of that view. What is the current accepted view of the target of selection? 

When you use the words “target of selection”, you are sort of anthropomorphizing the process, because selection is not some force that is out there. What we mean is what is unit of differential reproduction causes evolution. I think Dawkins is generally right. In almost every single case that we know of, we can reconstruct what happened and see the basis of evolutionary adaptation, and it’s basic the gene itself. Insecticide resistance in insects is a resistance against organophosphate insecticide and in many cases is the same gene, because we can localize where the lesion is on the gene that actually is causing resistance. In many cases, it is the exactly same mutation in different insects. That and in other many cases that we manage to localize where selection started, it’s on the gene level. That said, that are conceivably other targets of selection. Group selection, many have said as a plausible alternative, that is, it’s the group that has the differential reproduction. That’s been used to explain things from the evolution of altruism to sex. First of all, groups don’t proliferate and go extinct and fast as the individual. Second, I can’t think of an adaptation that is good for the group, but bad for the individuals, which you would expect to see if group selection occur overriding individual selection. I think Dawkins is pretty much right: the thing that has to change to cause evolution is the gene, but it does that by affecting the reproduction of the individual that carries that gene. In that way,  you can see the target of selection as the individual. You can think of the gene as the replicator, and the individual whose reproduction is affected by interacting with the environment as the vehicle for the gene .

Mayr was even critic of the definition that evolution is the change in the gene frequency. 

Most people think of evolution as observable changes in the organism over time, like dinosaurs evolving into birds. But, of course, that means there was a change in the frequencies of the genes. I prefer to look to evolution as the changes in the gene frequency, because you can have changes in phenotypes over time that aren’t what we called evolution. For example, the Japanese population has increased at least 6 inches in height, since the World War II, because the improvements in nutrition. I don’t think we called that evolution. Some people would, because they think evolution is change. But for biological evolution, which is what are talking about, ultimately you have to take that back to the gene frequency, because the Japanese population increase in height is not an example of biological evolution. I think Mayr was hanging up in a semantic there, because, after all, Mayr explicitly admitted to me “I don’t know anything about population genetics”. So, he preferred definition that comports more of his area, which is looking at phenotypic change.

You had mentioned the importance of other mechanisms other than natural selection in evolution, such as the genetic drift and sexual selection. What is their importance?  

Sexual selection is natural selection; it is a specific form of natural selection that involves mating. I don’t break that of from natural selection, but some people have tried to that. E.O Wilson tried to called it a separate evolutionary process. But it’s not, it’s the same thing. Genetic drift is a random change in the frequency of the genes due to stochastic reproductive differences, such as the differences in the sex ration, and differences in the number of offspring, that don’t have anything to do with fitness. Genetic drift is probably important in molecular evolution, because there are lots of characteristics in molecular evolution that its change don’t affect fitness, such as the parts of the DNA that don’t do anything, the so-called “junk DNA”. So, genetic changes in those regions are probably going to evolve only by genetic drift, because they can’t affect the reproductive outcome of the carriers. In the context of evolution of phenotypes, it is hard to prove that a trait evolved by genetic drift rather than selection, given that a tiny selection advantage can cause change over millions of years and you can measure that. The higher frequency of some deleterious genes in human populations like the Dunker and the Amish, the higher frequency of disease genes in Ashkenasi Jews can probably be attributed to genetic drift as well. But it is hard to give an example of that process operating in the observable traits of organisms. It probably operates, we just don’t have many good examples of it. There is also meiotic drive: when we have two different copies of the gene, when it’s time to make eggs and sperms, one copy kills the other one and that is represented in the next generation. But you can think of that as a kind of selection as well, although is not adaptive selection; it’s differential reproduction of the gene, it doesn’t make its carrier any better fit, in fact, it causes population to go extinct.  So, the two big forces of evolution are the deterministic force of natural selection and random force of genetic drift.

  

People think the only evidence we have for evolution is the fossil record, but even without the fossil record, evolution is true. So, what are the other ways to corroborate evolution? 

I think Dawkins made that point. We have enough evidence from other areas that we could document evolution without the fossil record. The evidence we have showing the organisms are related; the embryological data, that only makes sense in the light of evolution; the biogeographic data, which I described in my book, is very powerful evidence for evolution; vestigial organs; the existence of vestigial genes, the human genome has genes for making egg yolks and yet we don’t do it, those genes were inactivated. How do you explain that, unless we evolve from organisms that originally did make egg yolks, which we did? Ten years after Darwin, almost every biologist and rational lay person accepted evolution and yet there was no fossil record that actually showed evolution. But for many people the fossil record is the most convincing. When you can really show them a feathered dinosaur, that kind of evidence is very powerful. 

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* This paper is “A Pessimistic Estimate of the Time Required for an Eye to Evolve” authored by Dan-E. Nilsson and Susanne Pelger published in Proceedings of The Royal Society of London, Series B, 256, 53-58, 22 April 1994. The paper abstract is available on the link: http://rspb.royalsocietypublishing.org/content/256/1345/53.abstract.