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.
I was just reminded that in 2020 Hari Sridhar interviewed me about what is perhaps my most cited paper (1561 times to date, though my book Speciation with Allen Orr was cited almost six times as often), and certainly one of the few good ideas I’ve had in my life (the paper was also co-written with Orr). You can see the paper by clicking below, and there was a followup paper in 1997 with the word “revisited” tacked on the title below; that was written since new genetic-distance data had appeared.
Here’s the good idea as it came out in the interview:
HS: You were interested in Drosophila and the genetics of Drosophila right from the time of your PhD. What was the motivation for this particular piece of work?
Jerry Coyne: Well, the motivation is implicit in the paper. I was interested in the genetic basis of reproductive isolation in Drosophila. I realized that there were a lot of data out there on the genetic distances between different closely-related species of flies as measured by electrophoresis, and from reading a lot of the old literature – Patterson & Stone (1949, Univ. Texas Publ. 4920: 7-17), and The Genetics and Biology of Drosophila book series ‑that there is an immense amount of data on the crossability of flies, their sexual isolation, the sterility and viability of hybrids. And it came to me one day in Maryland – I can still remember this – that you could combine that different data using electrophoresis as the estimate of divergence time, and then the other parameters as estimates of the degree of reproductive isolation. By doing that, you could get some kind of estimate of the time course over which reproductive isolation evolves. After that, it was just a matter of compiling that data. It took a long time because it’s all in different places – papers, books and stuff. Nobody had thought to put them together before. It was just a matter of compiling the electrophoretic data with the crossability data and then seeing what came out of that. That was the motivation.
one more Q&A:
HS: At the time when you did this work, did you anticipate, at all, the kind of impact it would have on the field? Do you have a sense of what it mostly gets cited for?
JC: Yeah, it gets cited for the reason that we wrote it, actually. Well, two things. First, It gives an idea of the time course of speciation. But also, the result showing that sympatric species get reproductively isolated much more quickly, in terms of pre-zygotic isolation, than allopatric species, was unanticipated. It supports the idea that there’s either reinforcement or reproductive character displacement. I just said, well, let’s look at these data. Then we went back to all the original papers and looked at the ranges to see whether the species lived in sympatry or not. That was a lot of work too because, a lot of the time, range data is not presented as ranges.You have to look at where the flies were captured and, sort of, get an idea of whether the ranges overlapped or not. Those two aspects of the paper were important. Remember, the paper is incomplete because it leaves out a number of forms of reproductive isolation that could be very important in nature, like post-mating pre-zygotic isolation, sperm competition, ecological isolation and temporal isolation. Those aren’t included, because there’s no data. But the support for reinforcement that we showed, the high degree of pre-mating isolation between sympatric species as opposed to allopatric pairs, stimulated, stimulated, I think, work on reinforcement. Even in my own laboratory, my student, Daniel Matute, worked on reinforcement, I think, partly because of the data from this original paper. So it had a number of influences on the field. I don’t know how important it is. It’s a novel approach. It’s one that you can’t really us with most species because of the lack of crossability data. There have been a few other studies. Leonie Moyle did a similar study in tomatoes, I think, and Tamra Mendelson did a study on darters collecting information on genetic distance. The problem with darters and all other groups is that you just don’t have the ability to do laboratory crosses that you have in Drosophila. So Tammie was limited to about 12-13 species.
I’m sorry to say that I haven’t kept up diligently with other folks’ followup work, as there are more papers building on this one (e.g. here, here, and here). In general, I think, they’ve supported our main conclusions, especially the cool one that sexual isolation (mate discrimination) appears to evolve more quickly between groups that experience some period of “sympatry” (living in the same area) after speciation has begun. That in turn supports the idea of “reinforcement”: that if there is a reproductive penalty to hybridizing (e.g. producing hybrids that are sterile or weak), natural selection will build up mate discrimination so that the production of hybrids is less likely. (The idea is that you leave more of your genes to future generations when you produce healthy, conspecific hybrids, so any gene that favors mating with your own species will be favored.) And indeed, we found a strong pattern of heightened sexual isolation among species that are sympatric rather than allopatric (“geographically isolated”).
I liked the original idea of using genetic-distance data to figure out the time course of speciation (or rather, aspects of speciation: mate discrimination and hybrid sterility/inviability) because speciation is often very slow and reconstructing the process (and seeing if there are any generalizations to be made) can be done only by using proxies of divergence time, which in our case was the “genetic distance” calculated using gel electrophoresis. As I note in the interview, gel electrophoresis is pretty much dead, and DNA sequencing of fly species is the way to go.
The first article below is from a creationist website, Creation Evolution Headlines, and its author is a young-earth creationist. Oddly, though, its own headline and its discussion isn’t too far from what some “progressive” evolutionists maintain: evolutionary biology is racist, which explains the paucity of minorities in the field. The first paper, then, is not that different in its theses from the second and third papers below, although both were published in academic journa, Social Psychology in Education and in Evolution: Education and Outreach; and both papers include at least one evolutionary biologist as an author. Click headlines to read any of them.
In both papers religion is mentioned: African Americans are more religious than whites, and that makes them resistant to studying evolution. This may well be true, but I don’t know what to do about it. Here’s one anecdote I’ve told before. I was invited to lecture on evolution to a black “magnet school” (a high school) on Chicago’s South Side. At the end of my talk, a girl stood up and asked me if I was saying that Noah’s Flood and (as I recall) the Garden of Eden didn’t really exist. I had to tell the truth and say, “Yes, that’s what I think.” It caused a ruckus, and I could clearly see that the students became resistant to my message. (After the talk, the principal took me aside and said I really should have mentioned all the innovations that Africans had made, like inventing the airplane.)
But here’s from the paper:
In contrast to scientists, African Americans are significantly more religious than most every other American ethnic group. They also overwhelmingly self-identify as Protestant Christians. Thus, African Americans may be more likely than Whites to experience a major dissatisfaction with their pro-evolution courses and faculty. This perception could well affect their feelings about evolution classes and professors. In effect, African-American undergraduates appear to be more aware than Whites of the foundation of evolutionary theory which is
methodological (and de facto metaphysical) naturalism. Their religious inclinations will therefore be in conflict with the culture within the [evolutionary] community and it will be difficult for them to feel a sense of belonging in that community. The same with their moral objections to evolution, moral objections that are well founded in the African-American experience. The demands of methodological naturalism thus become an impediment to the greater participation of people of color in ecology and evolutionary biology.
Evidence exists that religiosity functions as a challenge to inclusion within evolutionary biology. Religiosity is negatively associated with exposure to evolutionary theory, knowledge about evolution, and acceptance of evolution. In a sample of African-American college students, Bailey found that the more religious the students were, the less knowledge they had about evolution. Moreover, religiosity is also associated with having moral objections to the theory of evolution. Thus, a cultural mismatch exists between the religious beliefs of students, and those of evolutionary faculty who are unable to properly deal with religious differences and moral objections to evolution. This may create a challenge that leads to a lower sense of belonging in fields of study that are entrenched in evolutionary thinking.
But if it’s “methodological naturalism” that religious people object to, they should object not just to evolutionary biology, but to ALL science. For “methodological naturalism” is simply the proposition that the laws of the universe are all that occurs in the sciences: there is no divine intervention. (This, by the way, is not an a priori decision of scientists to exclude God, it’s a method used because invoking God to explain natural phenomena never gets us anywhere. You all know the story of Laplace and Napoleon: “I had no need of that hypothesis”. Nor do we need The God Hypothesis now; it’s only an impediment to understanding.)
It’s not just evolutionary theory that’s founded on methodological naturalism, but all of science. If metaphysical naturalism makes you uncomfortable, then you have no business doing science at all.
More problematic is religiosity, since for some believers evolution poses no problem for their faith, but for others it’s an insuperable problem. Yet most Americans reject the naturalistic view of evolution: in fact, a 2019 Gallup poll (data below), a poll taken every few years, shows, that 40% Americans are young-earth creationists, another 33% are theistic evolutions (who believe that God helped evolution along, especially creating humans), while a mere 22%—a bit more than 1 in 5 of us, accept the naturalistic view of evolution as we teach it in college.
73% of Americans, then, think that God had some hand in evolution. That’s nearly 4 out of 5, and those objections are obviously religious ones. The biggest impediment to accepting evolution, as I wrote about in my Presidential paper in the journal Evolution, is religion. (As you can imagine, I had trouble getting this palpably true thesis published.) I know of no anti-evolution organization that is, at bottom, not based on religion, and there’s a negative correlation among U.S. states and among countries in the world between religiosity and acceptance of evolution.
With respect to minorities in particular, the “solution” that Bergman offers to the inequities in evolutionary biology is for us to learn to talk about religion and evolution:
O’Brien et al. [JAC: the paper below] concluded that
cultural differences in religiosity as well as the moral objections to evolution cannot be ignored in efforts to increase URM’s sense of belonging in EEB educational contexts (or other science fields that are rooted in evolution). A large proportion of the U.S. population is religious and disbelieves in evolution. African Americans and Latinos/as are more religious than the U.S. population as a whole and scientists in particular (Pew Research 2009a, b). One method to improve religious students’ feelings of belonging in EEB contexts might be teach EEB faculty to navigate conversations around religion.
Based on the studies below, and experiences of my colleagues, yes, black students or URMs (underrepresented minorities) are more wary of taking evolution classes because of their greater faith. What do do about that? Well, I have talked to students who had religious objections to evolution, but only in my office, not in class. And really, one has to be a therapist to deal with this issue. I can tell the students that many people find evolution compatible with their faith but, as you see from the figure above, most don’t. And if they ask me my own opinion, I will tell them that I don’t think religion is compatible with evolution, but, fortunately, I rarely got asked that by students.
Finally, the issue of eugenics comes up, as it does even in scientific societies. The mantra goes that evolutionary biology was founded on eugenics (no, it wasn’t), and that the discipline is still deeply imbued with eugenics (no, it isn’t). True, there was a period about ninety years ago when some evolutionists proposed eugenic schemes, but these schemes were not adopted wholesale by governments (and not at all in the UK), and those countries who did adopt them weren’t hugely influenced by evolutionary biology (if you want to blame any field for eugenics, blame genetics, but that’s hyperbole as well).
The quote below, reproduced in the paper above3 comes from the paper of Joseph Graves, Jr. (below):
During the same period in which African Americans were fighting for a legal end to Jim Crow, evolutionary biology became a coherent disciple. This occurred between 1936 and 1947 (Mayr 1982), with the founding of the Society for the Study of Evolution (SSE) occurring in 1946 (Smocovitis 1994). This was right after the end of WWII in which racial theories had been utilized to justify the slaughter of millions of people in both the European and Pacific theaters of the war. What is not as well realized is that these theories had their origin in the West and prominent evolutionary biologists and geneticists contributed to their rise (Graves 2005a).
First of all, evolutionary biology is not the sole source of bigotry (although in the past it has buttressed it), and the claim that evolution had something to do with the mass slaughters of WWII is either gross hyperbole or wrong. In every war, each side dehumanizes the enemy, and that began well before 1859. The slaughter of Americans by the Japanese and vice versa had nothing to do with evolutionary biology. Nor did the mass slaughters of Russians by Germans and vice versa, as well as Hitler’s Holocaust. And if you think evolutionary biology led to the Holocaust, read my colleague Robert Richards’ paper, “Was Hitler a Darwinian?“, free online. The answer is a firm “No!”
To blame past eugenics, or to bring up the Tuskegee experiment (a horrible and unethical study, though not an outgrowth of evolutionary biology) for racial inequities in evolution doesn’t comport with with any data I know of, nor with my own experimence. Has a single student ever said that if evolution had been involved with eugenics in the past, they’d be busy studying evolution now, sometimes with the goal of becoming an evolutionary biologist?
Click below to read the O’Brien et al. paper, and you can find the pdf here;
One of the factors these authors invoke as inhibiting minority participation in evolution is religiosity, and I’ll quote from this paper again:
Thus, challenges to inclusion that are likely the results of access to resources (e.g., knowledge, feeling comfortable outdoors) and challenges that are likely the result of real or perceived cultural mismatches between students and EEB faculty (e.g., religion) were both related to feelings of belonging. Moreover, the relationship between challenges to inclusion and sense of belonging remained after statistically controlling for ethnicity.
In addition, cultural differences in religiosity as well as the moral objections to evolution cannot be ignored in efforts to increase URM’s sense of belonging in EEB educational contexts (or other science fields that are rooted in evolution). A large proportion of the U.S. population is religious and disbelieves in evolution. African-Americans and Latinos/as are more religious than the U.S. population as a whole and scientists in particular (Pew Research 2009a, b). One method to improve religious students’ feelings of belonging in EEB contexts might be teach EEB faculty to navigate conversations around religion (e.g., Graves 2019).
Feelings of belonging are a hard one, for one has to figure out how to rectify that. Mentors would help, though, as Graves points out below, there are very few black evolutionary biologists. If you need a mentor of your own race to succeed, there are two ways to fix that. First, departments could practice affirmative action in hiring faculty (we’re doing that as hard as we can given the restrictions on the practice, though it’s now become illegal). The reason it hasn’t worked that well is that there aren’t many minority evolutionary biologists looking for jobs. (One reason, I think, it that it’s not a very lucrative field, but that’s just my take). The underqualification in STEM that leads to this inequity has only one fix that’s permanent: provide people with equal opportunity from birth. (There are other fixes that aren’t as good, like expanding outreach, and I’m in favor of them, but in the end the problem we need to solve is one that starts at birth, and there is precious little money or will to fix that.) The ultimate goal to me is equal opportunity, not equal outcomes, but the former is a lot harder to ensure. And of course given cultural differences and preferences, equal opportunity need not lead to equal outcomes.
Finally, Joseph Graves, an African American evolutionist, weighs in with this paper (click to read, pdf here).
His thesis is that current racism (i.e., ongoing “structural racism”) is what keeps minorities out of evolution.
The central premise of this commentary is that racism in America as it is manifested in higher education (specifically evolutionary biology) creates a culturally non-inclusive environment that systematically disadvantages persons of non-European descent. The form of this disadvantage differs by the sociocultural positioning of individuals. Thus to change the patterns of underrepresentation within the discipline requires that the dominant social group (persons of European descent socially-defined as “white”) to address and act on how their position of privilege is subordinating “others.”
I’d agree with him insofar as the qualifications of minority scientists were eroded by the history of slavery and racism, but I can’t agree that racism is pervasive in evolutionary biology right now. There are simply too many efforts to find and recruit minority and faculty students to support the view that the field is riddled with systemic racism.
And then there’s religion, with Graves indicting my own views:
Darwin’s agnosticism on the existence of God is a well-known feature of his life (Desmond and Moore 1991). Jerry Coyne’s position on the incompatibility of evolution and religion is one that I shared earlier in my career (Coyne 2012). However I have since recanted. Such views certainly stand as an impediment to the successful recruitment of greater numbers of African American students to careers in evolutionary biology.
I question whether my position or views like mine have kept students out of evolutionary biology. Can you find one student who says, “I would have become an evolutionary biologist, but Jerry Coyne convinced me that science and religion are incompatible, so I didn’t major in science or take an evolution course”? I doubt there are more than a handful of students in America who have even readFaith Versus Fact: Why Science and Religion Are Incompatible.” The recruitment of minority students into evolution may be because of religious belief that’s hard to overcome, but I doubt it’s because of the argument I made. That argument was not that religious people couldn’t accept evolution, or that scientists couldn’t be religious. Rather, it was that if you practice both science and religion, you are engaged in contradictory exercises: both fields are based on factual claims (religion, of course, is based on more than that), but only science has a way of determining whether those factual claims are true. This is a more sophisticated argument than simply saying, “Evolution makes a hash out of Christianity.”
I’m not denying, though, that religion is an impediment for black students to enter evolutionary biology; I have had colleagues teaching at various schools who told me they were explicitly told this by minority students. Graves, however, thinks it can be overcome with complex discussion:
However, this [religious belief] need not stand as impediment to the recruitment and retention of African Americans (or other highly religious) individuals into science. I have found that most of my highly religious Christian students have never really discussed the foundation of their theological views. As a confirmed Episcopalian, these are conversations I have learned how to conduct in ways that do not automatically shut down critical reasoning. Indeed, there is variation within Christian denominations with regards to their willingness to accept evolution as compatible with their faith. In general, doctrinally conservative Christians reject evolution (Berkman and Plutzer 2010). For example, the Southern Baptist Convention (formed as the Pro-segregation Baptist Church in the 1920s) and the National Baptist Convention (predominately African American membership) both reject evolution as compatible with their faith; on the other hand, the Catholic Church accepts evolution as compatible with their faith (Martin 2010). Notably there is variation within the individuals who subscribe to major denominations concerning their acceptance of evolution. For example, for Doctrinally Conservative Protestants, surveyed from 1994 to 2004, those who felt that: humans developed from earlier species of animals 76% felt that this statement was definitely false or probably false, while 24% felt it was probably true or true. Similar values were recorded for Black Protestants, 66% and 35% respectively, for mainline Protestant denominations, the values were 45% and 55%; while for Roman Catholics, the values were 42% and 58% (Berkman and Plutzer 2010). Thus while a given church’s official position is to accept or reject evolutionary science, individuals within denominations tend to make up their own minds concerning evolution. I have found that exposing my highly religious students to the fact that that there is variation within Christian thought concerning evolution helps them be able to engage it critically while not feeling that they are abandoning their faith.
Yes, that’s one way to do it, and it’s a lot easier if, like Graves, you’re religious. Another, which a colleague mentioned to me yesterday, is to say, “You don’t have to change your religious beliefs to take an evolution course. All you need to do is study the contents of the course and answer the questions.” (This works for required evolution courses.) Although this may seem callous, to me it involves less dissimulation, for, to be truthful, most Christians do believe something that’s incompatible with the theory of evolution, even if that belief is just that God helped the evolution of only one species along H. sapiens.
All of these authors (save Bergman) are well meaning, and I’m with their goal: everyone deserves a chance to study evolution. But the solutions involving religion, eugenics, affirmative action, and the like seem like Band-Aids on the wound.
There is only one workable solution, and that’s ensuring equal opportunity for all Americans. I won’t go into the problems with that solution, which may be insuperable, but should we be discussing that solution before we get to eugenics and religion?
Over the 14 years (can it be that long?) that I’ve been writing this website, I’ve put up several lists of misconceptions about or misrepresentations of evolution, but they’ve all been compiled by other people (for example, see here, here, and here). Some of them aren’t really misconceptions, such as the second link, which lists “misrepresentations” that are really pieces of advice about how to teach evolution. Those are generally good, though I can’t say I agree fully with this one: ““Avoid giving the impression that evolution is atheistic, or that evolutionists must be atheists.”
The way I teach evolution, starting with two sessions on why we accept evolution (these lectures were turned into Why Evolution is True), involves a certain amount of creationism-bashing. That’s because I use the rejection of creationism in favor of evolution in the late 18th century as an example of the way science proceeds: theories are discarded when they become increasingly incompatible with the evidence, while the alternative theory (evolution in this case) is able to explain facts that stymie creationism. The fossil record, anomalies of development, vestigial organs, and (my favorite) biogeography are all areas in which evolution explains phenomena that can’t be explained by Biblical creationism.
Now it wasn’t I who made this argument, but Darwin. If you read On the Origin of Species, which Darwin himself characterized as “one long argument,” you’ll see that he’s constantly opposing creationism with evolution without going too hard after Christian creationism (Britain wasn’t full of fundamentalists like America is now). Describing the imbalance of organisms on oceanic islands, for instance, was a very clever way that Darwin showed how evolution could explain phenomena that baffled creationists. In fact, I’ve never seen a good creationist explanation of biogeography, especially of the “unbalanced” nature of life on oceanic islands: the lack of endemic mammals, amphibians, and freshwater fish while there are plenty of endemic insects, plants, and birds.
But teaching this way offended a few of my religious students, who called me out for “creation-bashing” in my evaluations. I reject that criticism, for, after all, creationism was THE going explanation for life and its patterns before Darwin, and within a decade his compelling arguments had vanquished that explanation. Teaching this way, I think, is a good object lesson in how science is done (yes, creationism was a scientific hypothesis before Darwin), as well as educating the students on why nearly all scientists accept the fact of evolution. And I took this approach in Why Evolution is True. The usefulness of opposing two theories and adjudicating them with evidence is supported by the success of that book—far greater than I expected.
I don’t say anything about atheism in my classes, for that’s not part of my job, but most students do get the idea that the Bible should not be taken literally as a theory of biology. And if they ask me my views about gods straight out, I will be honest with them. Further, if they ask me, according to the guidance in bold above, whether religion and evolution (or science in general) are compatible, I will explain to them (privately, because the explanation is long) that while one can be religious and accept evolution, they are incompatible in a fundamental way: one accepts religious “truths” based only on authority, dogma, or scripture, while science accepts empirical truths based on evidence and the consensus of scientists. (Yes, religions do make truth claims.) That is why I wrote Faith Versus Fact. But I’ve never had a student complain that I’ve said that either evolution or science are atheistic, for I have never claimed that in lecture. It is of course true in an important way, for a practicing scientist rejects the idea that what he/she is investigating could have divine explanations. You leave your faith at the door of the lab. (I won’t reiterate my incompatibility claims here; read FvF if you want to see my argument.)
In that sense, then, science is atheistic, for it rejects belief in gods. Let me emphasize that, as I say in FvF, that this rejection is not by a priori agreement: scientists didn’t get together in some smoke-filled room and agree to reject gods, despite some creationists who claim that. Indeed, there were times in science, like early astronomy or when Biblical creationism reigned, that divine explanations were part of science. But since they haven’t proven useful in explaining anything, we now reject them as being useless. The best expression of this idea is the conversation that supposedly took place between the Emperor Napoleon and the French polymath Pierre-Simon Laplace in 1802, after Napoleon had been given Laplace’s five-volume work on celestial mechanics. There are many versions of this conversation, which may never have taken place, but here’s one from British mathematicial Walter Ball, published in 1888:
“Laplace went in state to Napoleon to accept a copy of his work, and the following account of the interview is well authenticated, and so characteristic of all the parties concerned that I quote it in full. Someone had told Napoleon that the book contained no mention of the name of God; Napoleon, who was fond of putting embarrassing questions, received it with the remark, ‘M. Laplace, they tell me you have written this large book on the system of the universe, and have never even mentioned its Creator.’ Laplace, who, though the most supple of politicians, was as stiff as a martyr on every point of his philosophy, drew himself up and answered bluntly, ‘Je n’avais pas besoin de cette hypothèse-là.’ [‘I had no need of that hypothesis.’]
Even if the conversation never happened, the anecdote explains why science is atheistic in practice: we have no need of that hypothesis.
But I digress. In August I’m lecturing to people on a cruise to the Galápagos Islands, which of course were visited by Darwin on the Beagle. I’m giving two lectures on that trip, “Darwin on the Galápagos” and “Why evolution is true”, as well as a Q&A session with two five-minute mini-lectures. But first let me point out two widespread misconceptions about Darwin and the Galápagos islands, which I won’t go into here but will do on the voyage:
Darwin did not have an “aha moment” in the Galápagos islands when suddenly evolution and natural selection became clear to him.
The famous “Darwin’s finches”, while they did play some role in Darwin’s thinking that led to The Origin, did not play a major role. He doesn’t even mention the finches in that book, and barely mentions the Galápagos (only 16 times). Other data and ideas were more important to the revolution in thought wrought by Darwin. If you want to read about his adventures on the islands, read Chapter XVII of the earlier The Voyage of the Beagle, “Galapagos Archipelago.” It’s free online at the link.
But I digress again. I have 5-10 minutes to explain to the guests what the biggest misconceptions about evolution are, so of course I have to leave some out. But the list is designed to inspire discussion, so here it is:
Evolution is “only a theory”
In evolution, everything happens by accident
Natural selection transforms individuals over time (in reality, individuals don’t change, but populations and species)
Evolution operates “for the good of the species”
Evolution is inherently progressive
Evolution equips organisms to face challenges that arise in the future
Humans are no longer evolving
I could of course give more, but these are the seven I’ve chosen to explain, and I hope I can do it in no more than ten minutes. (I’m leaving out details and hope that they’ll come out in audience discussion.)
I may give summaries of my other minitalks here later (on the ship I’ll ask people which one(s) they want to hear), which include “What evidence would disprove evolution?”, “What IS the theory of evolution?”, and “Why do so many Americans reject evolution?”.
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Here’s a first-edition of On the Origin of Species in a presentation copy. (I’m not sure what that is for the handwriting is surely not Darwin’s.) Only 1250 copies were printed, and this one goes for $950,000:
This is an example of science reporting that’s misleading—not because it gets the facts wrong, but because it oversells a rather mundane finding as a potentially important insight into the life of the extinct dinosaurs. And no, there’s nothing in the original paper—about a single “virgin birth” in a crocodile (really a “stillbirth”)—to suggest the Big Sell: that dinosaurs could have reproduced via “virgin births”, too. Dinosaur Jesus probably didn’t exist.
So here we have one new paper from the Royal Society’s Biology Letters; click on first screenshot below to read (the pdf is here) reporting the occurrence of parthenogenesis in one crocodile in one zoo. The NYT Trilobite reports about it in the second screenshot below (I found it archived here).
Parthenogenesis is a form of asexual reproduction that occurs without the fusion of a sperm and an egg. It occurs across various animal taxa, and can arise in different ways. Here’s what Wikipedia says about its distribution (note that it doesn’t occur naturally in mammals).
Parthenogenesis occurs naturally in some plants, algae, invertebrate animal species (including nematodes, some tardigrades, water fleas, some scorpions, aphids, some mites, some bees, some Phasmatodea and parasitic wasps) and a few vertebrates (such as some fish, amphibians, reptiles and birds).
Parthenogenesis can occur in a variety of ways, often after hybridization between species that produces an individual whose chromosomes can’t pair properly during meiosis (cell division producing sexual gametes). That mispairing increases the likelihood that an unfertilized egg in a hybrid can have a full chromosome complement and develop into an offspring. But in most other cases, like this one, asexual reproduction occurs as a modification of non-hybrid meiosis. That’s what apparently happened in this case.
The authors report that an 18-year-old American crocodile (Crocodylus acutus) in a reptile park in Costa Rica laid a clutch of 14 eggs. Candling of the eggs (holding them up to the light) revealed that seven apparently contained embryos (or dense spots), but none developed to hatching. One fetus, however, almost made it, and when the egg was dissected it contained a single female. Here’s the photo from the paper: mom on top and the fetus at the bottom. There was clearly something wrong with the baby as it failed to hatch, and I suspect it was simply screwed up.
(From paper): Figure 1. (a) Adult American crocodile, Crocodylus acutus. Photo courtesy of Q. Dwyer. (b) Stillborn fetus of American crocodile, Crocodylus acutus, Parthenogen. Photo courtesy of Q. Dwyer.
Genetic analysis of the fetal DNA compared to mom’s showed that they were pretty much genetically identical, with the fetus being, in effect, a clone of the mother.
How did this happen? If you don’t need the details, skip this next part between the lines.
DNA results from the paper suggest that the fetus came from fusion of two of the products of meiosis. Here’s a diagram of how a female produces an egg (or a male produces a sperm) during meiosis (figure from Wikipedia). It entails doubling of each of the chromosomes in a sperm or egg precursor cell followed by two bouts of cell division. The circle on the extreme left is of the precursor gamete cell in a species having four chromosomes, with two copies of each of two different chromosomes (remember, we have two pair of every chromosome). Then each pair doubles, which happens during normal cell division (mitosis) as well as in meiosis (second circle).
But then meiosis begins in gonadal cells: instead of each doubled chromosome splitting and going to a new cell, producing two genetically identical cells (this is normal cell division), the chromosome twins of each pair, now doubled (and having reshuffled bits from meiotic “recombination”), go into separate cells (third circle from left). This is the first phase of meiosis, or “meiosis I”. Now we have two daughter cells, each containing two chromosomes that are doubled but connected by the centromere. The chromosome number is really two, not four, because these doubled chromosomes (called “chromatids”) are going to go to different cells.
During “meiosis II”, the doubled chromosomes of each pair split, with each going to a new cell, so instead of two pair of joined chromosomes, we simply get two single chromosomes. The chromosome halves can sort out independently of each other, which is called “segregation”, and is one way to recombine existing genes. In the end, a cell with four chromosomes has, though doubling and then two cell divisions, produced a “haploid” cell with only two chromosomes. These final cells have only one instead of two copies of each chromosome pair. They are the gametes: eggs and sperm, and are shown on the extreme right. This happens in eggs and sperm, and when they fuse, the normal chromosome number is restored. You can see that when this happens in both sexes, you get novel combinations of parental genes—one of the likely reasons why sex evolved.
Now, how did this produce the parthenogenic crocodile fetus? In females, usually only one of the four products of meiosis goes on to form the haploid egg, with the other three cells being segregated into “polar bodies” that eventually die. But sometimes a polar body will fuse with the egg cell, restoring the normal chromosome complement and producing a diploid individual having two copies of each chromosome. It’s a bit more complicated than this , but the result is that a female can produce a normal diploid offspring without being fertilized. This is simply because two of the halved cells that would normally become egg cells fuse with each other.
Using DNA sequencing, the authors confirmed that this is what happened (the formal process is called “automictic parthenogensis with terminal fusion”). But the diploid fetus, which would normally go on to form a crocodile that would hatch, was somehow inviable.
Note that this is the first report of parthenogenesis in a crocodile. (Since the mother was 18 and had been alone since she was two, it was extremely unlikely that the fetus came from her storing sperm after being inseminated sixteen years before, as some animals can store sperm for a substantial period.)
So far so good. And the NYT article below gets the details and facts right. Where it goes off the rails is instantiated in the sub-headline. (The big headline is wrong, too: this is NOT a “virgin birth” but a virgin stillbirth. No new croc entered the world.
Because crocodiles are related to the extinct dinosaurs, author Greenwood (and the authors of the original paper), suggest that this is a case of “facultative parthenogesis that could also have occurred in dinosaurs! Dinosaurs could have reproduced asexually! T. rex could have produced baby T. rex copies without having to mate! Note the subheadline above, mentioning “Jurassic Park”.)
The article also says this:
So, did dinosaurs do it, as the discovery of parthenogenesis in crocodiles suggests? Parthenogenesis is best confirmed with DNA analysis, a process that has allowed scientists to tell it apart from delayed conception, where a female stores sperm for as long as six years before using it to fertilize eggs. Without the ability to retrieve dinosaurs’ and pterosaurs’ DNA, which does not persist in fossils, certainty is not available.
“We’ll never be able to prove they could do it,” Dr. Booth said. “But it suggests they had the ability.”
My response is “no, it doesn’t.”
But at least both the authors and the journalist say we can’t prove that there were Jesus-saurs, but I’d go further and argue that this is speculation far beyond what’s warranted from the data—speculation prompted by the desire to jazz up what is a decent but not terribly exciting result. In fact, I’d say that because the single dead offspring represents a bug and not a feature of croc reproduction, it says absolutely nothing about the likelihood that dinosaurs reproduced asexually, much less that they did so “facultatively”—as a regular evolved feature of their lifestyle.
First of all, this isn’t really “facultative parthenogesis,” which refers to species that can produce normal offspring sometimes via sexual reproduction and sometimes asexually. (That might be an evolved property, allowing an individual to pass on its genes when populations are sparse and there is nobody around to mate with.)
This isn’t what’s going on with crocs. What we see here is probably a rare developmental screwup (it hasn’t been reported before, despite there being many captive crocs), an anomaly that is an evolutionary dead end. Rare parthenogensis has been seen in other species too, including birds (see below), but in those species results in largely inviable or infertile offspring. True “facultative parthenogenesis” isn’t common, but does occur in some creatures like lizards. And it’s not a bug, but an evolved feature.
Below I show the family tree of some vertebrates, including the dinosaurs, birds, lizards (one of the “squamates” along with snakes), and the crocs. (This slide was created by my friend Phil Ward, who teaches evolution at UC Davis.) You see that the crocs are related to dinosaurs, but not as closely related as are living birds, which are a group (“clade”) phylogenetically embedded within the now-extinct dinosaurs.
The upshot is that a rare occurrence of asexual reproduction, especially when it leads to a dead or sterile offspring, says nothing about the likelihood of facultative parthenogenesis in a relative. After all, birds are more closely related to dinosaurs than are crocs, and a couple of birds have reproduced asexually (turkeys can produce fertile offspring this way, though rarely, and California condors have also done it). But nobody goes shouting from the rooftops “dinosaurs could have reproduced asexually” because of a few rare cases in birds. Quite a few lizards reproduce normally by parthenogenesis, but you don’t hear people extrapolating from lizards to dinosaurs, either. Even some fish reproduce parthenogenetically, so why not write that “because fish are related to dinosaurs, dinos could also have reproduced parthenogenically.”? It’s all pilpul.
The facts in the NYT report are accurate, including the caveat that we can’t test the asexual-dino hypothesis, but the author couldn’t resist bringing in the dinosaur angle—without any good reason to do so. What will happen is that people will ignore the fact that the single parthenogenic crocodile fetus was stillborn (or “stillhatched”), was probably just a rare developmental anomaly, and go away instead with the lesson that “DINOSAURS COULD HAVE REPRODUCED BY CLONING THEMSELVES!!!”.
Aposematic coloration, often called “warning coloration”, is the presence of bright or conspicuous colors or patterns in animals that are toxic, noxious, dangerous, or poisonous to predators. Here’s an example from Wikipedia, the granular poison frog (Oophaga granulifera). Like many dendrobatid frogs, this has a number of poison alkaloids in its skin, and they have been used in Central and South America to tip arrows or darts, which can kill mammals. Any predator that tried to eat one of these would probably be dead, or at least very ill.
My own frog, Atelopus coynei, looks conspicuous too [but see Lou Jost’s comment below], and may be toxic, but I don’t think people know anything about that:
Atelopus coynei. Photo: Jordy Salazar/EcoMinga
But of course far more animals than amphibians are aposematic. The skunk advertises its toxicity with a pair of conspicuous stripes. Many insects, like ladybugs and some leipidopterans, are also aposematic and toxic, including at least one bird species: see here for a Google image search of aposematic animals.
The colors and patterns, as the name implies, gives their bearers an evolutionary advantage over their presumably camouflaged ancestors, for predators will deliberately avoid the pattern, usually because they’ve learned to recognize and stay away from it because of previous unpleasant experiences. (The avoidance can also be evolved rather than learned, as you’ll see if you think about it. Even if eating one of these kills you, individual predators having less of a propensity to attack the pattern would be favored.) Usually, however, learning is involved.
But to get that advantage, the aposematic species has to be sufficiently numerous to afford predators a chance to learn and then avoid the next aposematic animal. And this creates an evolutionary problem.
We are pretty sure that aposematic species evolved from camouflaged ones. To get the warning coloration started, there have to be mutations in the camouflaged population that produce individuals with bright colors and patterns, at least in incipient form.
And that’s the rub: the first mutant individual stands a higher chance of being attacked and killed than do cryptic individuals. Even if it’s toxic, it may still get killed or injured by being attacked for being a novel, conspicuous creature. So how does the adaptation ever spread through the population from a rare initial state?
Previously, as described in the excellent Nature News & Views summary by Tim Caro below (click to read), we had a few answers:
1.) The trait could evolved by kin selection in gregarious animals. While the first mutant individual might be attacked, it might be part of a group of relatives that share that aposematic mutation. Assuming the predator learns to avoid the pattern after killing or hurting the first individual, it would avoid its similarly-colored kin, and that is a form of kin selection on the color/pattern genes that could make them spread.
2.) The trait could have evolved from a state that was conspicuous but not as conspicuous as the animals above. But this runs into the same problem as #1!
3.) The attacked aposematic mutant could avoid being killed by the predator because it smells or tastes bad, or is injured only slightly. If the predator learns from one experience (and some do), then that individual would henceforth be protected from predation, perhaps giving the mutant color/pattern gene an advantage. This seems somewhat likely, and could be tested by exposing naive predators to aposematic prey.
4.) Predators might avoid novel colors or patterns in general since the hunters have a search image for edible species. As Caro says, there’s some evidence for this, too.
But now, in his summary of the original paper, Caro describes a fifth hypothesis that is described in the Science paper below that. The authors test this interesting hypothesis using phylogenetic data, and it seems to be supported.
Click the original Science paper below to read about the novel hypothesis for the evolution of aposematism. The authors test it in amphibians, but may hold for other creatures as well. You can also find the pdf here , and the reference is at the bottom.
Again, I’ll try to be brief, but may not succeed. The authors’ hypothesis, which is very clever, is that full aposematic coloration may have evolved, at least in amphibians from an earlier state where it wasn’t clearly visible to predators. This could involve the colors/patterns starting their evolution on the BOTTOM (ventral) side of the animal, which wouldn’t draw attention until the animal was attacked, at which point it could flash its pattern and possibly startle the predator (the predator could also learn from a brief encounter that the prey was toxic). And the bottom-colored state could itself be of two types: small patches on the ventral surface (PV) or a fully colored ventral surface (FV). This is in contrast to an animal that is fully colored all over its body.
Once the predator started learning what the color/pattern means from the animals that had it on their belly, then the color could evolve to cover the animal, making it fully aposematic.
But how do you test this hypothesis? Well, you could see if predators learn to avoid toxic amphibians that had color patches painted on their belly, but there are few amphibians that are toxic and lack aposematic coloration. No, the authors tested their hypothesis by doing phylogenetic reconstruction: they used living species and their known family tree to deduce what the color/pattern of the ancestors were. This kind of reconstruction, which makes sense if you have enough data, is increasingly used to study evolution.
And so Loeffler-Henry et al. did a big reconstruction of the evolutionary history of amphibians, many of whom were aposematically colored. They used 1106 species, putting each in one of five evolutionary categories:
species cryptic (camouflaged; “cry” in photo below)
species PV (ventral side partly aposematic)
species FV (ventral side fully aposematic)
species fully aposematic all over its body (“conspicuous” or “con” in photo below)
species polymorphic (some individuals are aposematic, others not). There aren’t many of these, and I won’t go into why they are supposed to exist.
Here’s a photo from the paper showing four of the five states (a polymorphic species isn’t shown):
Part of paper’s caption: Cry: cryptic; PV (partially conspicuous venter): cryptic dorsum with conspicuous color present as small patches on normally hidden body parts; FV (fully conspicuous venter): cryptic dorsum with conspicuous colors fully covered on the venter; Con: conspicuous
And here’s the reconstruction of the phylogeny showing the position in the family tree of each of the five states. Click to enlarge:
(From paper): Fig. 2. Ancestral state estimation of each color state (N = 1106 species) in frogs and salamanders. Pie charts at each node show the probabilities of ancestral states. The ancestral state of frogs and salamanders is likely to be cryptic coloration. The hidden color signals (PV and FV) are widespread and have evolved multiple times in different lineages. PV: cryptic dorsum with conspicuous color present as small patches on normally hidden body parts; FV: cryptic dorsum with conspicuous colors fully covered on the venter. See table S11 for photo credits.
There’s a pie diagram at each node of the tree showing the probability that that ancestor had one of the five states scored. I won’t go into the methods for deriving probabilities (in truth, I don’t understand them); but her are the salient points:
1.) Ancestors tend to be cryptic (camouflaged; gray dots), with the possible exception of some salamanders. This comports with the evolutionary view that aposematic coloration was not an ancestral condition but evolved as a defensive adaptation to deter predators.
2.) Full aposematism—the orange state—didn’t appear until later in amphibians, and
3.) . . . it did so generally going through an intermediate state of aposematic coloration on the belly (purple and red species)
4.) The preponderance of purple circles earlier than red ones suggests that the condition of full ventral coloration was preceded in time by the evolution of partial ventral coloration: patches of color that could be flashed but are still less conspicuous to predators than fully belly coloration. This suggestion is supported by statistical analysis of the likelihood of the models, but I’ll skip that.
Now this is an analysis of amphibians, but could apply equally well to other species. In fact, many butterflies that have warning coloration have it on their rear wings, which are covered up when they’re resting. It’s only when they fly, or when a predator startles them, that the aposematic coloration is revealed. Here’s an example: an aposematic butterfly from Ray Cannon’s Nature Notes. It’s the common birdwing(Troides helena), known to be very poisonous since the larvae feed on plants containing toxic aristolochic acids.
(from site): Altinote dicaeus callianira – its distinct pattern advertises its unpalatability. Photo: Adrian Hoskins
For a long time the evolution of aposematic coloration posed the problem of what evolutionists call an “adaptive valley”: how do you get from one adaptive state (toxic but camouflaged) to a presumably more adapted state (toxic and brightly colored), when the intermediate evolutionary stage (the first mutant individual) was at a disadvantage: mired in an adaptive valley? This could not occur by natural selecction since selection cannot favor the less adapted (here, “less avoided”) individuals.
The authors propose a solution to this: an adaptive valley wasn’t crossed because the intermediate state—ventral coloration—did confer a selective advantage on the first mutant individuals.
The authors end the paper by suggesting that their scenario could apply to many species; and it well could:
. . . macroevolutionary studies on animal coloration should take into account these underappreciated hidden signals, which are both common and widespread across the animal kingdom, to advance our understanding of the evolution of antipredator defenses. Indeed, many animal taxa such as snakes, fishes, and a variety of arthropods (see fig. S12 for example groups) include species that are cryptic, are aposematic, and have hidden conspicuous signals. We therefore encourage follow-up studies in other taxa to evaluate the generality of the stepping-stone hypothesis as a route to aposematism.
As I wrote in April, India’s National Council of Educational Research and Training (NCERT), decided to remove evolution—a great unifying theory of biology—from all science classes below “class 11”, , which means that only students who have decided to major in biology will learn about evolution. (Indian students begin specializing younger than do American students.)
. . . . evolution used to be part of science class in “Classes 9 and 10,” which in India are kids 13-15 years old. After that they take exams and have to decide what subjects to specialize in: science (with or without biology), commerce, economics, the arts, and so on. Specialization begins early, before the age at which kids go to college in America.
In India now, only the students who decide to go the Biology route in Classes 11 and 12 will get any exposure to evolution at all! It’s been wiped out of the biology material taught to any kids who don’t choose to major in biology.
The deep-sixing of evolution was originally part of the whittling-down of the Indian school curriculum during the pandemic, but now it appears to be a permanent change, and not just in public schools, but also in many private ones, who follow the same standards set by the ICSE (Indian Certificate of Secondary Education).
But it’s gotten worse. NCERT has eliminated not only evolution from most secondary school science classes, but have also deep-sixed the periodic table (!), as well as sources of energy and material about air and water pollution. (One would think those topics would be relevant in a country as crowded as India.)
This is all reported in a new article from Nature (click on screenshot for a free read):
An excerpt:
In India, children under-16 returning to school at the start of the new school year this month, will no longer be taught about evolution, the periodic table of elements, or sources of energy.
The news that evolution would be cut from the curriculum for students aged 15–16 was widely reported last month, when thousands of people signed a petition in protest. But official guidance has revealed that a chapter on the periodic table will be cut, too, along with other foundational topics such as sources of energy and environmental sustainability. Younger learners will no longer be taught certain pollution- and climate-related topics, and there are cuts to biology, chemistry, geography, mathematics and physics subjects for older school students.
Overall, the changes affect some 134 million 11–18-year-olds in India’s schools. The extent of what has changed became clearer last month when the National Council of Educational Research and Training (NCERT) — the public body that develops the Indian school curriculum and textbooks — released textbooks for the new academic year starting in May.
Researchers, including those who study science education, are shocked.
Not only that, but NCERT didn’t get input from parents or teachers, or even respond to Nature‘s request for comment. Here’s what’s gone besides evolution:
Mythili Ramchand, a science-teacher trainer at the Tata Institute of Social Sciences in Mumbai, India, says that “everything related to water, air pollution, resource management has been removed. “I don’t see how conservation of water, and air [pollution], is not relevant for us. It’s all the more so currently,” she adds. A chapter on different sources of energy — from fossil fuels to renewables — has also been removed. “That’s a bit strange, quite honestly, given the relevance in today’s world,” says Osborne.
A chapter on the periodic table of elements has been removed from the syllabus for class-10 students, who are typically 15–16 years old. Whole chapters on sources of energy and the sustainable management of natural resources have also been removed.
They’ve also bowdlerized stuff on politics:
A small section on Michael Faraday’s contributions to the understanding of electricity and magnetism in the nineteenth century has also been stripped from the class-10 syllabus. In non-science content, chapters on democracy and diversity; political parties; and challenges to democracy have been scrapped. And a chapter on the industrial revolution has been removed for older students.
And here’s NCERT’s explanation, which doesn’t make sense at all.
In explaining its changes, NCERT states on its website that it considered whether content overlapped with similar content covered elsewhere, the difficulty of the content, and whether the content was irrelevant. It also aims to provide opportunities for experiential learning and creativity.
First, evolution is NOT covered elsewhere, nor is it that difficult in principle. You don’t even have to teach natural selection; you can just give people the evidence for evolution, which is hardly rocket science. And the periodic table? That’s hard? How else will students learn about the elements? As I said, only students age 16 and above will even hear about evolution or the elements, and most students in India will not go on to college where they can also learn these things. Remember, only high-school-age (in the U.S.) students who decide to specialize in science will learn about evolution, the periodic table, and energy.
And these cuts may well be permanent:
NCERT announced the cuts last year, saying that they would ease pressures on students studying online during the COVID-19 pandemic. Amitabh Joshi, an evolutionary biologist at Jawaharlal Nehru Centre for Advanced Scientific Research in Bengaluru, India, says that science teachers and researchers expected that the content would be reinstated once students returned to classrooms. Instead, the NCERT shocked everyone by printing textbooks for the new academic year with a statement that the changes will remain for the next two academic years, in line with India’s revised education policy approved by government in July 2020.
At first I thought the dropping of evolution reflected the Hindu-centric policies of Modi, somewhat of a theocrat, but an Indian biologist (see earlier post) told me this was unlikely, as Hindus aren’t particularly offended by evolution. The reasons must lie elsewhere, but they’re a mystery to all of us. However, Joshi does that the dumping of evolution reflect in part some religious beliefs:
Science educators are particularly concerned about the removal of evolution. A chapter on diversity in living organisms and one called ‘Why do we fall ill’ has been removed from the syllabus for class-9 students, who are typically 14–15 years old. Darwin’s contributions to evolution, how fossils form and human evolution have all been removed from the chapter on heredity and evolution for class-10 pupils. That chapter is now called just ‘Heredity’. Evolution, says Joshi, is essential to understanding human diversity and “our place in the world”.
In India, class 10 is the last year in which science is taught to every student. Only students who elect to study biology in the final two years of education (before university) will learn about the topic.
Joshi says that the curriculum revision process has lacked transparency. But in the case of evolution, “more religious groups in India are beginning to take anti-evolution stances”, he says. Some members of the public also think that evolution lacks relevance outside academic institutions.
And here’s one more suggestion: that some of these ideas are “Western”—truly the dumbest reason ever not to teach them. So what if Darwin was British?
“There is a movement away from rational thinking, against the enlightenment and Western ideas” in India, adds Sucheta Mahajan, a historian at Jawaharlal Nehru University who collaborates with Mukherjee on studies of RSS influence on school texts. Evolution conflicts with creation stories, adds Mukherjee. History is the main target, but “science is one of the victims”, she adds.
So here we have the world’s largest democracy dumbing down its curriculum, making some of the greatest ideas in science unavailable to its citizens. This is unconscionable, but there’s little those outside of India can do about this. The only thing I can think of is to is tell Richard Dawkins, who can at least embarrass the government by tweeting about this. Otherwise, there are no petitions to sign, nobody to protest to. And millions of Indian kids will be deprived of the greatest idea in biology.
Aron Ra has asked me to be on his live video podcast tomorrow, and I’m glad to oblige. It will be about evolution. As Aaron told me:
Ideally, we would like to do a half hour of you talking about your career in defense of science against creationism. Then we would do another half hour of taking selected questions from the chat.
The show is at 10 a.m. Chicago time (11 a.m. Eastern time) tomorrow, and you will be able to watch it by clicking on the link below.
UPDATE: I’m told the video will be out next Tuesday, so if you want audio and visuals (recommended), I’ll put the YouTube conversation up then
__________
Not long ago I did a podcast (which I think will eventually become a video) with the young writer, musician, and podcasthost Coleman Hughes, who has a Substack page, a YouTube page, a homepage that lists his video podcasts, a list of all his audio podcasts, and, on top of all that, he’s a rapper and plays jazz trombone. His political views seem to be of the McWhorterian/Lourian stripe: heterodox from a minority point of view, which of course draws flak. I found him a delightful interviewer, wanting to talk about evolution along with everything else—and he came well prepared to discuss it.
We talked for a bit over an hour, and you can hear our conversation by clicking on the screenshots below. As always, I can’t listen to myself talk, so I heard about two minutes before I had to turn it off. Perhaps you’ll be able to stand more of it, so I’ll put it up here.
Here’s Coleman’s summary of the interview:
My guest today is Jerry Coyne. Jerry is an evolutionary biologist and geneticist. He received his PhD from Harvard in 1978, after which he served as a professor at the University of Chicago in the Department of Ecology and Evolution for over two decades. His seminal work is on the speciation of fruit flies. Jerry is also the author of two books, including “Why Evolution Is True”, which is also the name of his blog, and “Faith Versus Fact”.
In this episode, we talk about the tension between evolution and the biblical origin story. Jerry goes over the basics of the theory of evolution by natural selection. We talk about sexual selection. We talk about the teaching of intelligent design in schools and how that compares to the battle over CRT in schools today. We dicuss the attack on evolutionary psychology from the political left. We discuss epi genetics and the concept of intergenerational trauma. We talk about how humanity has evolved genetically in recent history and the consequences of birth rate differences between different groups of people. We talk about gender dysphoria and gender ideology. Finally, we go on to talk about the unanswered questions that remain in the field of evolutionary biology.
When you click on the screenshot, you’ll be taken to a site where you can access the conversation:
Unfortunately, NPR has gotten hold of Agustín Fuentes, who seems to have a strong ideological slant on biology, to explain to its listeners the “problems” with using DNA tests for ascertaining your ancestry—as many of us have done with companies like 23andMe™. Sadly, Fuentes’s “criticisms” of the method and results are misguided, bespeaking either an ignorance of biology or an ideological drive to convince people that humans around the world are so similar that it’s next to useless to use DNA to find out your ancestry. (This is, of course, part of the view that “race is a social construct”, which apparently now means “ethnic groups can’t readily be identified by their DNA.”)
To cast doubt on such tests, Fuentes makes a number of claims: races (or ethnic groups) are social constructs; we don’t have enough data to reliably identify groups from their DNA (ergo we don’t have enough data to reliably determine your genetic origins); that one doesn’t expect to find genetic differences between geographically separated populations because geography is purely subjective and arbitrary; that people move around too much to reliably determine the location where one’s ancestors lived; that your genealogical history may diverge from your genetic history; and that the best that ancestry tests can do is tell you what genetic diseases you may be prone to. To sum up all the misguided information that Fuentes gave in his 14-minute interview with Regina Barber, I’ll first give one paragraph from Fuentes’s interview:
So I will tell you right now, my 23andMe tests miss a bunch of my actual kin – right? – because, like, most of your ancestors contributed no genetics to you – right? – because of the way genetics mixes down and across. And here’s the punchline for ancestry testing. It actually can tell you some information. When it comes to certain diseases, it’s actually really important to know, but it does not tell you who you are, and it actually doesn’t tell you who your ancestors are. It tells you which peoples from different places contributed to your genetics. But that is not your family, right? Your genealogy is more than just the biology.
Now we’ve met Fuentes before and I’ve taken issue with his distortions of biology (see here for some posts), especially those insisting that Darwin was a racist and that there is no such thing as a sex binary. What worries me, especially in this NPR interview, is how Fuentes, perhaps in the interest of ideology, has repeatedly misled the public. In my view, the NPR interview does damage the public understanding of an important area of modern genetics.
But hear (or read) for yourself. The short NPR show (14 minutes) can be found by either clicking on the screenshot below and then by listening to the show, or by reading the transcript here.
I had an email discussion with my colleague Luana Maroja at Williams College about this, for the two of us have co-written a paper on this and similar topics that will be out in a month. She gave me permission to use her name and her words, and so I’ll put her words in indented italics and mine flush left in roman type. Fuentes’s statements from the interview are indented in roman type.
First, a few words about the supposed inability of using DNA to determine one’s ancestors. Although it’s true that most genetic variation occurs within rather than between populations (this was first popularized by my advisor Dick Lewontin), and that 99.9% of the DNA between any pair of humans is identical, people don’t realize that that still leaves a substantial amount of genetic difference between people, and especially between populations, that can be used diagnose ancestry. We know this because the human genome has 3.3 billion base pairs, and even 99.9% identity leaves 3.3 million differences among individuals.
And research has shown that a lot of those differences occur between geographic populations. (I use either that pharse or “ethnic group” instead of “races” because we know that the classical idea of races as absolutely geographically demarcated groups, profoundly genetically differentiated,and diagnosable using few genes—is wrong.) But differences between populations become clear when you use a large group of those 3.2 million segregating base pairs (SNPs, or “single-nucleotide polymorphisms”), and these can be used to tell you where your genes come from. If it was way off the mark, companies like 23andMe would be out of business.
For example (do check out the links for yourself):
a.) Even the old and outmoded view of race is not devoid of biological meaning. A group of researchers compared a broad sample of genes in over 3,600 individuals who self-identified as either African-American, white, East Asian, or Hispanic. DNA analysis showed that these groups fell into genetic clusters, and there was a 99.84% match between which cluster someone fell into and their self-designated racial classification. This surely shows that even the old concept of race is not “without biological meaning”. But that’s not surprising because, given restricted movement in the past, human populations evolved largely in geographic isolation from one another—apart from “Hispanic”, a recently admixed population never considered a race. As any evolutionary biologist knows, geographically isolated populations become genetically differentiated over time, and this is why we can use genes to make good guesses about where populations come from.
More recent work, taking advantage of our ability to easily sequence whole genomes, confirms a high concordance between self-identified race and genetic groupings. One study of 23 ethnic groups found that they fell into seven broad “race/ethnicity” clusters, each associated with a different area of the world. On a finer scale, genetic analysis of Europeans show that, remarkably, a map of their genetic constitutions coincides almost perfectly with the map of Europe itself. In fact the DNA of most Europeans can narrow down their birthplace to within roughly 500 miles.
b.) Here’s a genetic cluster analysis (using principal-components analysis of many genes from many Italian populations, nicely separated by geography (the paper is here). This is based on only about 270 variable SNPs in 210 genes studied in 1736 individuals. Although there’s been some mixing (overlap between clusters), in general you would be able to localize where in Italy a person was from by looking at even a relatively small sample of their DNA variants. Why the different groups? They reflect the history of colonization and settlement in different parts of Italy as well as local population structure due to mating with those born close to you. Clearly, migration has not been sufficient to efface these historical differences. You get similar maps if you look at the three links above, which cover both Europe and the whole world.
c.) You can also place people pretty accurately using variation within transposable (“mobile”) genetic elements, as you can see in this figure using a cluster (principal components) analysis of MEVs, or mobile element variation. Populations fall out genetically very well according to the continent from where the individuals were sampled (the Nature paper from just 12 days ago is here). Continental areas are coded this way: AFR, African; AMR, American; EAS, East Asian; EUR, European; SAS, South Asian. And remember, this is only DNA sequences in moving elements. If you use every bit of DNA in whole genomes, you get much cleaner results.
(If you added positions of these elements, you’d get even more information, but the analysis above seems to depend on DNA sequences alone, which aren’t ideal for MEV’s because they have are so many repeats.) Still, look at how just a small sample of the genome can give you pretty good diagnostic ability.
How many SNPS do companies like 23andMe use? Over a million variable sites (see here). That gives substantial diagnostic ability to determine where one’s ancestral genes came from. Not only that, but since we know the gene order, you can use that to find your relatives, for relatives not only have similar variants, but also have the same sets of variants grouped together on their chromosomes, as “linked” gene variants aren’t broken up by recombination within a generation or two. My own 23andMe analysis found several distant cousins, and when I checked with my sister, sure enough, they were indeed my cousins. This would not be possible unless the variation had some biological significance. You can diagnose ancestry with good accuracy, but you can also find your relatives! (Because of “linkage disequilibrium” between sites, you can even “paint” the chromosomes based on geographic ancestry, showing recombination that happened in your ancestral lineage).
Now that I’ve told you the fallacy of Fuentes’s insistence that DNA testing is severely compromised because most humans are genetically identical, I’ll turn you over to Luana, who knows a lot more about this stuff than I do, as she not only does it herself, but teaches it to her undergraduates. She analyzes (her words in italics, again) a number of Fuentes’s claims, and, actually, finds the whole interview deeply misleading about DNA testing. Note that her words are reactions to what Fuentes said in the interview.
FUENTES: So here’s the deal. When you spit in a tube and send them – let’s take 23andMe – your DNA, they analyze your DNA – this little, teeny piece of it – right? – they don’t analyze all of it – and they file that in storage. It’s like, you know, a compartmentalized cluster of information. These are reference populations. These reference populations – the data they have are how they place your DNA and tell you something about it.
. . . This ability to take your spit and put it in a tube, pay someone 150 bucks and have them send you something back about your DNA – that is amazing. But what it tells you – when they send you back your results, that splash page is never accurate because the thing it should say on that splash page is, congratulations, you are 99.9% identical to every other living human. That’s not what it tells you.
LUANA: He seems to ignore that they use SNPs (single nucleotide polymorphism) rather than whole genome sequencing. Well, because they only use informative sites (SNPs)—the sites that vary among individuals and populations—and not the sites that are 99.9% identical among people, they cannot actually come back with a result saying “you are 99.9% identical to all humans”. The SNPs they actually use in determining ancestry are the variable sites alone, the 0.1% of the human genome. And because they categorize people NOT by race, but by geographic location, Fuentes’s criticism of race as a social construct also falls apart.
FUENTES: Yes. There are tens of thousands, if not hundreds of thousands of idealized reference populations in humans. So it sure as heck doesn’t tell you where you are in the human panoply of genetics.
LUANA: Then he goes on to say there would be more populations if they sequenced more people – but this is not the point. The populations nearby would still be the most genetically similar because of strong isolation by distance – so you could subdivide more (for instance, now Italians can be further subdivided between south, middle and north), but that would not change the fact that if your DNA says you are most closely related to people descending from the Italian peninsula, that doesn’t mean you may be more closely related to North Europeans, because Italians are more closely related to each other than to North Europeans.
JAC: One of the biggest flubs in Fuentes’s argument is his claim that continental areas, because (he says) they are demarcated subjectively, they aren’t really expected to have much correlation with genetic differentiation. But in fact that’s how genetic differentiation occurs: by lack of gene flow between geographically isolated populations, which causes them to evolve in different directions. He picks out the only “arbitrary” geographic division I know of between continents to make his point. But even that divide, between Europe and Asia, is not purely subjective: it’s usually at the Ural Mountains, which are a geographic barrier.
FUENTES: A reference population is a cluster of individuals who have their DNA sequenced from some geographic place – continents, big geographic space. So Africa, Asia and Europe are not biological units, right? They’re not even single geobiological patterns or areas or habitats or ecologies, right? They are geopolitical. We named them. We created these landmasses and divided them in certain ways. So for example, what is the difference between Asia and Europe?
BARBER: Other than geographic location?
FUENTES: No, when does Asia become Europe?
BARBER: Oh, I don’t know.
This is cherry-picking nonsense. Of course the geographical demarcation between Europe and Asia is somewhat arbitrary (though it does involve a mountain barrier, but this does not mean that you can’t tell a European from people in various parts of Asia). And of course the other regions: the Americas, Polynesia, Australia, Africa, and so on, are geographically isolated. The difference between Europe, Asia, and Africa, or between Australia and the Americas, is not arbitrary. Further, the presence of genetic continuity is clear in DNA information, with more significant geographic barriers usually usually leading to greater population structure.
Luana chimes in:
LUANA: Then one more bit of nonsense – because we named continental regions – it does not mean they were not “regions”. In fact, our geopolitical nomenclature usually follows geographic lines pretty closely – rivers, mountains etc. And the categories of 23andMe are not sociopolitical locations – they are geographic locations – not countries. These include the Iberian peninsula, Great Britain, east Asia etc. Not to mention that political and linguistic boundaries also have a huge effect on gene flow. I am baffled about why Fuentes is even talking about subjective “geopolitical boundaries.”
FUENTES: The problem is that they don’t actually tell you from the get-go how human you are – right? – 99.9% identical to everyone else. It’s 0.1% that varies across humans – 0.1% of our DNA. They don’t tell you sort of how that actually varies. They tell you you are X percentage African, Asian or European because we think of continents – we think of Africa, Europe and Asia as places that reflect biologies, that reflect deep lineages in humanity. And that’s not true. So the danger in these tests is reifying that. You say, like, oh, I’m 17% African. Wow, I’m 17% Black. Those two things are not the same, right? If you have 17% ancestry, let’s say, from Africa on a test from 23andMe, most – and you’re here in North America, most likely, you have some genetic ancestry in populations from West Africa, right? That’s interesting. That’s fascinating. That’s important. But that doesn’t mean you have any relation to anyone in South Africa or East Africa or Central Africa or North Africa. Africa is not a biological unit. There is no gene for race because race doesn’t come from biology. It comes from racism.
LUANA. More nonsense. He says, “But that doesn’t mean you have any relation to anyone in South Africa or East Africa or Central Africa or North Africa. Africa is not a biological unit. There is no gene for race because race doesn’t come from biology. It comes from racism.”
This is ridiculous – A sub-Saharan African population is indeed more closely related to other populations from that area than to populations from other areas, for genetic mixture between Sub-Saharan African and other groups was impeded by the Sahara. In all principal components analyses, sub-Saharan African populations appear as tight clusters, differing even from other African populations, with additional diagnostic differences seen within locations in the sub-Saharan cluster. So, I think what he means is that you won’t have close family members in Africa, for we’re talking about the kind of ancestry that dates back thousands of years, not a couple generations.
Luana found this 2011 paper from the European Journal of Human Genetics that shows the genetic structure of African and non-African populations. Notice that all sub-Saharan African populations in this principal-components analysis group together at the right (dark green), and are separate from northern African populations (orange), while European populations (blue), South Asians (pink), east Asians (light green), Pacific Islanders (yellow) and the Americas (tan). While there is some mixing, you can see that in general, the genetic clusters correspond to geographic localities, and sub-Saharan African populations are one of the most isolated of them all. (Also notice now similar this SNP map is to the map of movable genetic elements shown above: genetic information from different sources converges to a similar structure set by past population history).
(from the paper, subfigure a): Figure 1 PCA of merged HGDP and Hap Map 3 samples. Panels show the results of the PCA for the full merged set of SNPs (460 147 SNPs) (a), for random subsets of 100 000
JAC: One of Fuentes’s misleading beefs is that human migration largely nullifies any value in DNA testing:
FUENTES: But what it can tell us is where do you map related to these reference populations? What does the movement of humans look like? And the best thing they’re doing now is you can ask, sort of, well, where was I – where do my ancestors – genetic ancestors – where were they 200 years ago? Where were they 2,000 years ago? Where were they 10,000 years ago? And guess what? They’re different places. Now, humans throughout history – right? – for at least the last 3- to 500,000 years, humans and our most recent ancestors have been moving around and having sex with each other regularly. Humans do that. And that’s what we’re from.
LUANA: And then this empty statement: “Now, humans throughout history – right? – for at least the last 3- to 500,000 years, humans and our most recent ancestors have been moving around and having sex with each other regularly. Humans do that. And that’s what we’re from.” Sure, who said otherwise?? This is exactly what 23andMe gives you – the mixing, for it assumes mixed ancestry. What Fuentes is leaving out is that human populations are also quite quick to regain genetic structure after replacement events (due to the very low ancestral migration distances in our species) and after settlement, humans tended to disperse very little until the invention of rapid transportation starting with horses and now with airplanes.
JAC: One more argument Fuentes makes against assessing your ancestry via DNA testing is that his own personal ancestry changed over time as he took repeated tests. This argument implies that, say, a test you take now may be completely off the mark:
FUENTES: The cool thing about these tests is that they’re constantly updating their reference populations. So really cool part of this is that once you’ve done it, Ancestry.com, 23andMe or any of the other companies keep going back because as they expand their reference populations, lo and behold, your genes change. Everything changes about you. I – it’s basically – they just get more information, so they know better about you. So, for example, I’ve been watching myself slide around, like, the Iberian Peninsula, North Africa, way over into Arabia, down into Sudan, back up, back over. And then lately I’ve been shoved, like, way up into Russia. But what’s interesting is that you learn more and more about all of the movement of those peoples that contributed to you and how we are all mutts and how we’re all this blend of amazingness
LUANA: Finally the very thing he says:“I’ve been watching myself slide around, like, the Iberian Peninsula, North Africa, way over into Arabia, down into Sudan, back up, back over” simply shows the huge progress the sites are doing for identification. When I first sequenced my DNA, I came out as partially east Asian. Nowadays I have no East Asian, it is all Native American – in the past they did not have enough information to finely break these two related groups, now they do. This is progress. Unlike Fuentes’s insinuation, this means the dataset is getting more robust and that it’s easier to finely locate people to smaller regions.
(Luana is from Brazil but has mixed ancestry from within the Americas.)
Jerry here again: Fuentes’s presentation on this NPR show makes the listener think that the real value in DNA testing is not the “slippery” business of finding out where your ancestors come from, but what genetic diseases you have. He raises a number of “problems” with tests like those used by 23andMe, but these are not serious problems. And by concentrating on the similarity between humans, without emphasizing that there are several million sites in the DNA that can be used to diagnose ancestry as well as to find your relatives, he’s neglecting the fact that it is those millions of variable sites that are the ones that CAN BE AND ARE used to detect your ancestry—and we know now that they do so with substantial accuracy, as the data above show.
Fuentes’s deliberate neglect of genetic differentiation between populations that are geographically isolated or isolated by distance and by cultural “inbreeding”—the way we diagnose ancestry—can only be understood as an obfuscation due to either ignorance or ideology. If you adhere to a certain ideology, populations cannot be allowed to show diagnostic genetic differences because that means that populations are different, and thus that populations could be unequal. And thus they could be superior or inferior. This sliding from “difference”, which is indisputable, to “ranking”, which need not happen at all if you’re rational, is why “progressive” ideologues oppose the emphasis on diagnostic genetic differences between human populations. It is another case of reading into nature what you would like to see in nature.
And that is why Barber starts her interview with Fuentes this way.
BARBER: And aside from leaving out our similarities, most of these tests spit out results based on large, geographic locations – so continental ancestry. The problem is that these kinds of results – think African, European, South Asian – are then linked to race, a social construct.
No, we’re not talking about race or social constructs here: we’re talking about geographic populations, and which ones contributed genes to your own DNA.
Finally, because it’s so cool, here’s the genetic map of Europe compared to the geographic map, taken from the 2022 PNAS paper cited above. The genetic data, presented again as a principal components analysis on the right, are based on 5,500 individuals and 204,652 SNPs (single-nucleotide polymorphisms). Isn’t the coincidence between the genetic and geographic maps remarkable? This shows that migration has not effaced historical data, and that you don’t need obvious geographic barriers to get distinguishable clusters.
(From the paper): A sample of European structure in the UKBB. (A) The number of individuals included from each European country analyzed. Countries are grouped by geographic region; these regions are chosen as a means of group representation and do not necessarily imply historical links. Sample sizes from each region are also shown. Abbreviations are as follows: SE Europe (southeastern Europe), S Europe (southern Europe), E Europe (eastern Europe), C Europe (central Europe), N Europe (northern Europe), W Europe (western Europe), Brit. & Ire. (Britain and Ireland). (B) The sample counts for each European region. (C) The first two PCs calculated by PLINK of 5,500 European individuals. Individual genotypes are shown by letters that encode the alpha-2 ISO 3166 international standard codes and are color coded according to geographic region. The median PC for each country/region of birth is shown as a label. Plots were generated using the ggplot2 package (65) in the R statistical computing language (59).
And that, ladies and gentlemen, brothers and sisters, and comrades, is how we can make fairly accurate guesses about where your genes (and distant ancestors) come from.
UPDATE: Within a minute of pressing “post,” I got this notice from 23andMe, saying that they’d located putative relatives of mine, including one second cousin and three third cousins. I’ll check with my relatives!
