Decolonizing evolution (and Darwin) was inevitable

July 9, 2020 • 11:20 am

When I said that “Darwin was next” in the line of statue-removal, renaming, and accusations of racism, I wasn’t kidding. Darwin was an abolitionist, but he did evince some white superiority in his writings and letters, calling blacks “savages” and “barbarians” (I lecture on this). It’s only a matter of time before that bigoted paternalism, ubiquitous in 19th-century England, would bring Darwin down.

It’s starting:

Dr. Schierenbeck is a plant geneticist, taxonomist, and evolutionist at California State University, Chico.

I looked up “decolonization” on Wikipedia and found this:

Decolonization (American English) or decolonisation (British English) is the undoing of colonialism, the latter being the process whereby a nation establishes and maintains its domination on overseas territories. The concept particularly applies to the dismantlement, during the second half of the 20th century, of the colonial empires established prior to World War I throughout the world.[1] Scholars focus especially on the movements in the colonies demanding independence, such as Creole nationalism.

Then I went to the online Oxford English Dictionary, and found only one definition of “decolonize”, which is below:

So clearly the tweeter is not using “decolonize” in the dictionary sense.

So what does it mean to “decolonize” evolution? As the tweet suggests, it’s an effort to demonstrate that the ideas adumbrated by Wallace (evolution by natural selection, biogeography as a result of evolutionary processes) and Darwin (evolution, natural selection, gradualism, common ancestry, and splitting of lineages) were anticipated by people in other cultures. I know of antecedents in the West (Patrick Matthew’s suggestion of natural selection is one, as was Erasmus Darwin’s suggestion of evolution), but you’ll look long and hard outside of England before failing to find anything close to the fullness of Darwin”s and Wallace’s ideas.

Why is this being done, though? I can see only a motivation to do down the uniqueness of their contributions by showing that “other people thought of them before”—and not just other people, but “other cultures.”  It’s not a dispassionate search for antecedents, it seems, but an effort to rope others into the corral with Darwin and Wallace—to empower other cultures by saying they had the idea first.

Good luck with that! You may be able to find someone from a non-Western culture who suggested that animals and plants might have changed over time, but that’s not “decolonizing” Darwin, for Darwin did so much more than just suggest that idea. He fleshed it out extensively, worked out the implications, supported his ideas with copious evidence, answered objections, and suggested further tests. The Origin was sui generis, and rightfully deserves its place as the founding document of evolutionary biology. As T. H. Huxley said when he first read it, “How extremely stupid not to have thought of that.” And indeed, nobody else had—save Wallace with his ideas about natural selection (misguided, in my view) and Patrick Matthew with his sketchy musings.

But none of this suggests that Englishmen were smarter than anybody else. The idea of evolution was “in the air,” so to speak, but found its natural (and best) expositor in Charles Darwin, who had the wealth, the leisure, the personal experience, and, above all, the brains to put it all together.

h/t: Isabelle

My talk in Tallahassee in late March

February 25, 2020 • 12:00 pm

In almost exactly one month, I’m speaking to the Tallahassee Scientific Society in Tallahassee, Florida. My talk is on Thursday, March 26, and I think the time and venue are the same as those for the previous speaker: 7 p.m. at Tallahassee Community College’s Center for Innovation on Kleman Plaza. The topic is “Why Evolution is Still True”, and I’ll give a brief rundown of the evidence for evolution (updated in light of new discoveries), followed by discussion of why Americans remain so resistant to this scientific truth.

I’ll give one more announcement in mid-March or so, and all are welcome to come. I believe they’ll also have my two trade books on sale, which I’ll be glad to autograph. And, if you tell me the genus and species of any felid besides the house cat, I’ll draw a cat in it.

Here’s a photo I sent them to use for advertising the talk; the picture is from Wikipedia so it’s in the public domain. Toes, teeth, and size!

Photo credit: H. Zell (from Wikimedia Commons; CC license CC BY_SA 3.0).


Live Long and Evolve

July 12, 2019 • 10:15 am

by Greg Mayer

Much of the time while Jerry was in Hawaii, I was traveling in New York and New England, including attending Evolution 2019 in Providence, RI, the annual joint meeting of the Society for the Study of Evolution, the American Society of Naturalists, and the Society of Systematic Biology. The opening night is highlighted by the Stephen Jay Gould Prize Public Outreach Lecture. The Prize is given for “sustained and exemplary efforts [that] have advanced public understanding of evolutionary science and its importance in biology, education, and everyday life”. This year’s Prize winner was Jerry’s erstwhile Ph.D. student Mohamed Noor of Duke University.

Mohamed Noor in his Starfleet uniform. (Which show is the uniform from?)

The title of his lecture was “Evolution in the Final Frontier: Why Might We See So Many Humanoid Aliens in Star Trek?” He delivered it to a packed house, some in Starfleet uniform. (The opening night is open to and advertised to the general public.) Mohamed is the author of Live Long and Evolve (Princeton University Press, 2018), and his talk dealt with one of the topics in the book.


Some of Star Trek‘s writers have been renowned science fiction authors, and the franchise has long been known to pay attention to the scientific commentary about the series. My favorite example of this is the “Heisenberg compensator“. When it was pointed out that Heisenberg’s uncertainty principle (which states that either the position or the velocity of a particle could be known, but not both) meant that transporters would have a hard time doing what they are supposed to do, Star Trek writers invented the “compensators”, which, in some unknown fashion, overcame this difficulty.

Mohamed’s talk dealt with another such issue: why do alien species from all over the galaxy look so much alike? And so much like us? You know—roughly bilaterally symmetric, 4-limbed, bipedal, encephalized, the head with eyes, ears, nostrils, a mouth. The aliens might be a different color, or have head ridges, even antennae, but they look very human. The short, and probably pragmatically correct, answer is that the aliens had to be played by human actors, and anything else would be either undoable, prohibitively expensive for a TV series, or both. But Star Trek wanted a principled answer.

Image result for star trek humanoid aliens
A diversity of humanoid Star Trek aliens. From

The principled answer that I knew of came from The Next Generation series, in which a species-diverse group of current humanoids encounter a recording made by an “ancient humanoid“, which explains that they had “seeded” planets across the galaxy with DNA that would drive evolution on those planets in a humanoid direction. It was never explained how this would work.

Mohamed’s careful study of Star Trek encountered two other explanations, both in the original series: humans derive fairly recently from visiting alien astronauts; or, aliens (most of them anyway) are derived from life on Earth. Rather than give Mohamed’s choice from among these three which is most plausible given what we know about evolution and genetics, I’ll leave it as an exercise for readers to think about, or debate in the comments (or, you could read his book!).

I’m about halfway through the book now, and as a long time Star Trek fan, I am fascinated. I have not yet gotten to the chapter which discusses all those interplanetary hybrids (like Mr. Spock), and am looking forward to it. In the book, Mohamed usually introduces each topic with a Star Trek scene touching on an evolutionary or genetic topic, and uses that as a launching point to discuss the biological principles involved. Among the topics he covers are common ancestry, phylogenetic trees, natural selection, convergence, genetic drift, what DNA is, and how DNA ‘works’. And I’m not finished yet!

The book is aimed at the general public (i.e., it is not a textbook), and Mohamed gives the most generous reading possible to Star Trek‘s scientific forays—it is not a compilation of errors. Footnotes give references to further Star trek episodes, and references in the comprehensive endnotes cover the scientific literature very well, including in areas outside Mohamed’s own areas of research. Many of these references are to the latest literature; the suggested reading adds more accessible works, including Dawkins’ Blind Watchmaker, and, of course, his mentor’s Why Evolution Is True. In fact, near the beginning of his lecture, he gave a shout-out for WEIT (the book).

Mohamed has long used science fiction to teach science, and been much involved in outreach activities, as regular WEIT readers will recall. In 2017, the Evolution meetings and Heroes and Villains Fan Fest/Walker Stalker Con were both being held simultaneously in Oregon Convention Center, and Mohamed attended both! You can see videos of him engaging scientific topics through science fiction here, here, and here, and a Star Trek vs. Star Wars debate. There are also a number of videos of his students making presentations at his Youtube channel.

Teaching Evolution: Sewall Wright: Evolution in space

March 9, 2019 • 10:30 am

by Greg Mayer

Our next installment of Teaching Evolution for this spring concerns Sewall Wright. His contributions were wide-ranging, but he is most noted for his integration of population structure (population size, migration) and selection into what he called the “shifting balance” theory. In this theory, genetic drift, migration, and selection interact to produce what he saw as the most favorable conditions for evolutionary advance. The reading is a brief precis of his much longer 1931 paper in Genetics, but in many ways was more influential, as it exposed a wider audience to his ideas. Modern appreciations of the shifting balance theory are given by Nick Barton (2016) and Norm Johnson (2008).

Sewall Wright, with guinea pig.

Sewall Wright (1889-1988) was, along with R.A. Fisher and J.B.S. Haldane, one of the founders of theoretical population genetics, which synthesized Mendelian inheritance with Darwinian natural selection, thus laying the foundations of modern evolutionary biology. His classic paper “Evolution in Mendelian Populations” (Genetics, 1931) laid out his synthesis, and led to his election to the National Academy of Sciences while still a young man. Like Darwin, Wright studied carefully the work of animal breeders, and this strongly influenced his ideas on evolution, which he called the “shifting balance” theory. Although sometimes caricatured as a theory emphasizing random genetic drift, Wright stressed the importance of the interaction of drift, selection, and migration in adaptive evolution. Wright strongly influenced Dobzhansky, and he coauthored five papers in the latter’s “Genetics of Natural Populations” series. Beginning with his graduate studies at Harvard, Wright’s organism of choice for genetic studies throughout his career, which ended with a very productive 33 year retirement at the University of Wisconsin, was the guinea pig (note what is in his left hand in the photo). He is author of the monumental four volume Evolution and the Genetics of Populations (1968-1978). William Provine has edited a collection of Wright’s most important papers, Evolution: Selected Papers (1986), and written an insightful and analytic biography, Sewall Wright and Evolutionary Biology (1986).


Wright, S. 1932. The role of mutation, inbreeding, crossbreeding, and selection in evolution. Proceedings of the Sixth International Congress of Genetics 1:356-366.

Study Questions:

1. In this paper, Wright introduces the idea of a fitness surface or adaptive ‘landscape’ (see esp. Fig. 2). What do the x and y axes (the two dimensions of the ‘map’ on the paper) represent? What does the ‘altitude’ of a point on the landscape represent? What does a peak in the landscape represent? What does a valley in the landscape represent?

2. In one sentence in the first half of the paper, Wright succinctly states the Hardy-Weinberg equilibrium for allele frequencies, and its cause. Find and quote the sentence. Show that Wright understands the H-W principle.

3. Why is it difficult for a species to evolve across a valley from one peak to another if selection is the only evolutionary force? How does this lead Wright to argue for the importance of drift (inbreeding) and migration (crossbreeding), as well as selection, in allowing species to reach the highest adaptive peaks?


Jerry addendum:  While Wright’s theory was influential, and was incorporated by Theodosius Dobzhansky into his view of the Modern Evolutionary Synthesis (see his book Genetics and the Origin of Species), I find the theory deeply flawed. With two colleagues, Nick Barton and Michael Turelli, I wrote a long critique of that theory in 1997. Our paper was in turn criticized in two papers, one by Mike Wade and Charles Goodnight, and the other by Steven Peck et al.  We then rebutted these papers in another Evolution paper in 2000. All four references and links are below.

In my biased estimation, our critique did stem the tide of enthusiasm for Wright’s theory; in fact, Wright’s colleague James Crow at Madison said that our paper prompted him to stop accepting that theory. I’m not sure whether Greg mentions the critiques and attempted rebuttals in his lecture, but I’m putting them here for readers.

Coyne, J. A., N. H. Barton, and M. Turelli.  1997.  A critique of Sewall Wright’s shifting balance theory of evolution.  Evolution 51:643-671.

Wade, M. and C. J. Goodnight. 1998. The theories of Fisher and Wright in the context of metapopulations: when nature does many small experiments. Evolution 52:1537–1553.

Peck, S. L., S. P. Ellner, and F. Gould. 1998. A spatially explicit stochastic model demonstrates the feasibility of Wright’s shifting balance theory. Evolution 52:1834–1839.

Coyne, J. A., M. Turelli, and N. H. Barton.  2000.  Is Wright’s shifting balance process important in evolution? Evolution 54: 306-317.


Teaching Evolution: Theodosius Dobzhansky: Genetics of natural populations

February 27, 2019 • 10:30 am

by Greg Mayer

Readers may recall that last spring I began what Jerry called a “mini-MOOC” on evolutionary biology. Because I began making posts fairly late in the semester, I got to only seven installments before the semester ended. I’m teaching the same course, BIOS 314 Evolutionary Biology, this spring, and so I’d like to start up again.

In the class I have the students read a series of what I regard to be classic papers or extracts–—one each week—and these are what I want to share with WEIT readers. Each reading is accompanied by a brief biography and illustration of the author, and a small number of study questions, designed to guide the student in understanding the reading. I sometimes assign these questions as homework essays, or include them on exams. When possible, I will provide links to the readings. The installments so far have been Charles Darwin, A.W.F. Edwards, George Gaylord Simpson, Charles Lyell, Alfred Sherwood Romer, Alfred Russel Wallace, and Richard C. Lewontin. We pick up with Theodosius Dobzhansky. Dobzhansky was a key figure in the “Modern Synthesis” of evolutionary biology in the 20th century (as described below). Jerry had intended to do his doctoral work with “Doby” (as he was known later in his career; students from earlier knew him as “Dodik”), but wound up studying with Dick Lewontin, who had been a student of Doby’s, and thus Jerry is Doby’s academic grandchild.

Theodosius Dobzhansky (1900-1975) was a Russian-American geneticist who was arguably the most important evolutionary biologist of the 20th century. Completing (although never formally receiving) an undergraduate degree at the University of Kiev, he began his career conducting field studies of coccinellid beetles and laboratory experiments on Drosophila. In 1927 he received a fellowship to come to America and work with T. H. Morgan at his famed “fly room” at Columbia University. As a geneticist working at the epicenter of American genetics, Dobzhansky was well aware of the important empirical and theoretical advances being made in genetics; as a field worker and experimentalist, he was able to tie these developments more closely into the phenomena of natural populations. He synthesized the theoretical, experimental, and field approaches in his classic book Genetics and the Origin of Species (1937). It was through this book, much more so than through the previous synthetic, but more theoretical, works of Fisher, Haldane and Wright, that the biological community as a whole became aware of the developments in evolutionary biology, and the book inspired an outpouring of work carried on in the same synthetic spirit. Dobzhansky is well known for his two aphorisms, “Nothing in biology makes sense except in the light of evolution”, and “Heaven is where, when the experiment is over, you don’t need statistics to figure out what happened.” His major works include Genetics and the Origin of Species (3rd ed., 1951), Mankind Evolving (1962) and Genetics of the Evolutionary Process (1970). His monumental 43-paper series on the “Genetics of Natural Populations” (1938-1975) has been reprinted, with extensive historical and biographical commentary, as Dobzhansky’s Genetics of Natural Populations I-XLIII (1981), edited by Lewontin, Wallace, Moore, and Provine.

Dobzhansky, Th.1951. Genetics and the Origin of Species. 3rd ed. Columbia University Press, New York. Excerpts from Chap. III. “Mutation in Populations” (pp. 50-55, 70-75) and Chap. V. “Adaptive Polymorphism” (pp. 108-123, 129-134).

Study Questions:

1. What is blending, as opposed to particulate, inheritance? What are the consequences of the two sorts of inheritance for the evolutionary process? What analogy does Dobzhansky use to illustrate the effect of blending inheritance?

2. How does Dobzhansky see the “stored” genetically variability of natural populations and the generally deleterious nature of mutations nonetheless leading to populations being adapted to their conditions of existence?

3. Can a phylogeny be estimated for infraspecific variants? [We usually think of phylogeny being estimated for species, so that we can say, for example, lions and tigers share a more recent common ancestor than either does with the house cat. But could we construct a phylogeny for, say breeds of house cat? Or subspecies of tiger? Or mitochondrial haplotypes of the lion? See Dobzhansky’s Fig. 4 (p. 113 in the reading) for his answer.]

4. What is balanced polymorphism? How does balanced polymorphism relate genetic variability and natural selection?


Human Phylogeography

February 23, 2019 • 11:33 am

by Greg Mayer

For the spring semester, my colleague Dave Rogers and I are teaching a seminar class entitled “Human Phylogeography.” Phylogeography is the study of the history of the genetic variation, and of genetic lineages, within a species (or closely related group of species), and in the seminar we are looking at the phylogeography of human populations. DNA sequencing now allows a fine scale mapping of the distribution of genetic variation within and among populations, and, remarkably, the ability to sequence ancient DNA from fossil remains (including Neanderthals). The seminar is based primarily on a close reading of David Reich’s (2018) Who We Are and How We Got Here (published by OUP in the UK).

A Krapina, Croatia, Neanderthal woman, photo by Jerry.

Although rarely under that rubric, human phylogeography has been a frequent topic of discussion here at WEIT, by Jerry, Matthew, and myself, including our several discussions of Neanderthals (or Neandertals) and Denisovans. So it may be of interest for WEIT readers to follow along. Below the fold I’ve placed the course syllabus, which includes the readings, and links to many newspaper articles of interest, and online postings, including many here at WEIT, and also from John Hawks Weblog, a site we’ve recommended on a number of occasions when discussing human evolution. (The newspaper links appear as images; just click to go to the story.) We just finished our third meeting, and I’ve been quite impressed by the students’ discussion and writing. We’re fortunate to have some students from anthropology or with some anthro background.

Please read along with us, or browse what seems interesting below. If you have questions or comments, post them here, and I’ll be looking in.

Continue reading “Human Phylogeography”

Teaching Evolution: Richard C. Lewontin: The genetic basis of evolutionary change

May 10, 2018 • 11:00 am

by Greg Mayer

Our seventh installment of Teaching Evolution is an extract from The Genetic Basis of Evolutionary Change by Richard C. Lewontin. As regular WEIT readers will know, Dick was Jerry’s Ph.D. dissertation advisor (and mine too in the de jure sense, since my de facto advisor, Ernest E. Williams was retired). In this book, Dick summarized and critiqued the initial results of the “find ’em and grind ’em” school of population genetics, which studied electrophoretically detectable allelic variation in soluble proteins. In the extract chosen, he lays out the basic questions of population genetics, and how, historically, they have been addressed. It turns out that protein electrophoretic data were inadequate to our needs, leading to a further “struggle to measure variation”, leading eventually to nucleotide sequencing.  The last of Dick’s books mentioned below is a collection of reviews from the New York Review of Books; it contains “Sex, Lies, and Social Science” (and the subsequent exchange), which along with Peter Medawar’s takedown of Teilhard de Chardin, and E.E. Williams’ takedown of Soren Lovtrup, is among the best book reviews ever.

Richard C. Lewontin (b. 1929) is Alexander Agassiz Professor of Zoology Emeritus in the Museum of Comparative Zoology at Harvard University. One of the most influential population geneticists of the 20th century, he studied under Th. Dobzhansky at Columbia. His work has centered around what he has called “the struggle to measure variation”, and the interpretation of that variation in terms of the evolutionary forces acting on populations. In 1966, he and Jack Hubby at the University of Chicago, and, independently Harry Harris in England, introduced the technique of protein gel electrophoresis to the study of genetic variation in natural populations and showed that there is abundant variation in nature. His student Marty Kreitman was the first to use DNA sequencing to study variation, which, like electrophoresis before it, has revolutionized empirical population genetics. Lewontin’s books include The Genetic Basis of Evolutionary Change (1974), Human Diversity (1982), The Triple Helix (2000), and It Ain’t Necessarily So: the Dream of the Human Genome and Other Illusions (2000).

Lewontin, R. C. 1974. The Genetic Basis of Evolutionary Change. Columbia University Press, New York. Extracts from Chap. 1, “The Structure of Evolutionary Genetics” (pp. 3-6), and Chap. 2, “The Struggle to Measure Variation” (pp. 19-38 and pp. 86-94). (access to entire book)

Study Questions:
1. What does Lewontin see as the most essential part of Darwin’s contribution? Why does this contribution make the study of genetic variation crucial for the study of evolution?

2. What are the “classical” and “balance” schools of population genetics? What are the views of these schools on the nature and amount of variation in natural populations, the modes of natural selection acting in natural populations, and the genetics of speciation?

3. What degree of variability in populations is inferred from the study of visible mutations, and from the study of the results of artificial selection? How do these estimates compare to one another?

4. How would DNA sequences, as opposed to mere identification of protein alleles (as is done in electrophoresis), provide richer information for addressing the questions posed by Lewontin? In particular, how would they provide better data on the nature of selection? (The answer to this is not in the reading.)

Teaching Evolution: Alfred Russel Wallace: Geographical distribution

May 2, 2018 • 12:30 pm

by Greg Mayer

Our sixth installment is a paper by Alfred Russel Wallace. Written while he was still collecting in the Malay Archipelago, it is a foundational work in zoogeography, in which Wallace invokes a long history of evolutionary changes of organisms, and geographical changes of the land and water, to account for organisms’ current distributions and affinities. Readers may recall that 2013 was the centenary of Wallace’s death, and that we posted a series of commemorative posts on Wallace here at WEIT to celebrate his accomplishments during that year.  (Follow this link for many WEIT postings on Wallace.)

Alfred Russel Wallace (1823-1913) was co-discoverer, with Charles Darwin, of natural selection. A gentleman but from a family of lesser means than Darwin, he was largely self-taught. He first made a name for himself by conducting an expedition to the Amazon (1848-1852) with Henry Bates; unfortunately, most of his specimens were lost when his ship sank on the return to England. Setting out again on a natural history collecting expedition, he traveled in the Malay Archipelago from 1854-1862. It was at Ternate in 1858, that, during a bout of malaria, the concept of natural selection came to him. Wallace is widely acknowledged as the greatest figure in the history of zoogeography. A lifelong friend of Darwin, in later life he became a staunch public advocate of socialism and, much to the chagrin of his scientific colleagues, spiritualism. His books include The Malay Archipelago (1869), Contributions to the Theory of Natural Selection (1870, a collection of his papers, including the important ‘Sarawak’ and ‘Ternate’ papers), his monumental The Geographical Distribution of Animals (1876), Island Life (1880), and Darwinism (1889). Andrew Berry has edited a wide ranging anthology of Wallace’s writings, Infinite Tropics (2002).  All of Wallace’s published works are available at John van Wyhe’s superb Wallace Online.  A modern, scientific biography is Peter Raby’s Alfred Russel Wallace: A Life (2002).

Wallace, A.R. 1860. On the zoological geography of the Malay Archipelago. Journal of the Proceedings of the Linnean Society, Zoology 4:172-184.

Study Questions:
1. The comparison of which particular islands’ faunas helped Wallace epitomize the nature of the boundary between the Indian (= Oriental) and Australian regions? What are the geographic, climatic, and geological circumstances of these islands? What are their faunal differences and similarities?

2. What importance does Wallace place on the depth of the sea? Show how he uses it in accounting for the geographical distribution of animals.

3. What explanatory principles does Wallace invoke to explain the phenomena he discusses? What do these principles reveal about Wallace’s thinking at the time he wrote this paper?


Teaching Evolution: Alfred Sherwood Romer: Life’s story

April 25, 2018 • 11:30 am

by Greg Mayer

Our fifth installment of Teaching Evolution is a paper by A.S. Romer describing a new species of mammal-like reptile that has a dual jaw joint– the old reptilian one, plus a nascent mammalian one. (In reptiles, the jaw joint is between the quadrate bone of the skull and the articular bone of the lower jaw; in mammals it’s the squamosal and dentary, respectively. We’ve discussed this previously at WEIT.) The transition from reptiles to mammals is one of the most completely exemplified major evolutionary changes in the fossil record. That the ancestors of mammals were to be sought among a particular group of fossil reptiles (synapsids) has been known since the late 19th century, from the work of British anatomist Richard Owen and American paleontologist Edward Drinker Cope. Since then, the story of how this transition occurred, with the bones of the reptilian jaw joint   becoming ear ossicles in mammals, while a new jaw joint evolved, has been worked out in exquisite detail. This paper by Fuzz Crompton and Farish Jenkins gives an overview of the story, and this paper by Luo Zhe Xi has the latest developments.

In the readings I give to the students in my evolution class, I like to include some papers reporting particular findings (such as this one), as well as review papers or book extracts (such as the earlier installments). Most of the scientific literature is, of course, reports of particular findings.

Alfred Sherwood Romer (1894–1973) was for many years the dean of American vertebrate paleontology. A student of William King Gregory at Columbia University, he spent much of his early career at the University of Chicago, before moving to Harvard’s Museum of Comparative Zoology. At the MCZ, he eventually became director, in which position he recruited to the Museum such luminaries as G. G. Simpson and Ernst Mayr. Unlike these colleagues, however, Romer devoted most of his work to the study of evolutionary history, rather than evolutionary mechanisms, publishing on vertebrates of all kinds and times, but specializing on amphibians and reptiles of the Paleozoic and Triassic. He wrote several highly influential textbooks and monographs, including Man and the Vertebrates (1st ed., 1933), Vertebrate Paleontology (1st ed., 1933), The Vertebrate Body (1st ed., 1949), and Osteology of the Reptiles (1956). Edwin Colbert (1982) gives a brief summary of his life and work.

Romer, A.S. 1969. Cynodont reptile with incipient mammalian jaw articulation. Science 166:881-882. (This will get you the paper only if you or an institution you are affiliated with has a subscription; if not, judicious inquiry might yield you a copy.)

Study Questions:
1. Why is Diarthrognathus, despite its possession of a double jaw joint, not considered an evolutionary reptile-mammal transition form? What, according to Romer, is the phylogenetic position of Probainognathus, and why does he think so?

2. Given what you know about paleogeography, what do you think about the fact that cynodonts (advanced mammal-like reptiles) of the early Triassic are found in South Africa, while the even more advanced cynodonts described from the Middle Triassic by Romer are from South America?

3. What skeletal feature has reached an essentially mammalian stage in Probainognathus and its relatives (the chiniquodonts)?
[The other installments of Teaching Evolution can be found by clicking ‘MOOC’, under “filed under” or “tags”, just below.]

Teaching Evolution: Charles Lyell: The principles of geology

April 19, 2018 • 10:45 am

by Greg Mayer

Our fourth installment of Teaching Evolution is an extract from Principles of Geology, by Charles Lyell. Lyell was an enormously influential scientist, and a leading figure in scientific circles in 19th century Britain. His influence on Darwin was profound: in Janet Browne’s authoritative biography of Darwin, the entry for Lyell in the index of volume one goes on for 28 lines, and for 27 lines in the second volume!

In the first half of the 19th century, the links between biology and geology were much closer that they are now. Both were branches of natural history, and Darwin first made his name as a geologist, before his more biological contributions came to dominate his reputation. Lyell’s Principles were required reading for anyone involved in discussions of organic evolution. The current divorce between the academic disciplines is regrettable.

When I was helping plan a major in ecology, evolution, and conservation a few years ago, a survey of a broad range of the best undergraduate majors across the United States showed that none required any geology (though many required years of chemistry and/or physics). A notable innovation of our new major was that it required foundational work in geology for students in the biological sciences. (The major, unfortunately, was nixed by our dean before it got implemented.)

Charles Lyell (1797-1875) is perhaps the greatest geologist of all time. As the American paleontologist David Raup once remarked, “Lyell is to geology what Darwin is to biology.” Lyell’s signal achievement was to turn geologists to the study of observable physical, chemical, and biological processes, and to make these processes the first choice when seeking explanations for the events of Earth history. His method may be epitomized by the phrase “the present is the key to the past”. Born in Scotland and trained as a lawyer, for most of his life he supported himself and his family by the sales of his books. A close friend of Darwin’s, he helped arrange the first publication of Darwin’s views on natural selection, alongside Wallace’s independent discovery of the same principle. Despite this, Lyell did not accept evolution until several years after the publication of the Origin. Lyell’s masterwork, Principles of Geology (1st ed. 1830-1833), which went through 11 editions in his lifetime, was informed by his wide field experience in Europe and North America. He is buried, like Darwin, in Westminster Abbey.

Lyell, C. 1830-1833. Principles of Geology, Being an Attempt to Explain the Former Changes of the Earth’s Surface, by Reference to Causes Now in Operation. Three volumes. John Murray, London. Vol. 3, Chaps. I, IV.

Study Questions:
1. What does Lyell identify as the chief impediment to the first geologists achieving a sound theory of the Earth’s history?

2. What types of studies have led to progress in geology?

3. How may the relative ages of rocks be determined? What sort of evidence does Lyell consider the most useful in this regard?

4. What does Lyell mean by a “zoological province”? How does he use this concept to help establish chronology?

[The other installments of Teaching Evolution can be found by clicking ‘MOOC’, under “filed under” or “tags”, just below.]