Macro vs Microevolution: side comments on Phylogeny

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From Douglas Erwin:

Arguments over macroevolution versus microevolution have waxed and waned through most of the twentieth century. Initially, paleontologists and other evolutionary biologists advanced a variety of non‐Darwinian evolutionary processes as explanations for patterns found in the fossil record, emphasizing macroevolution as a source of morphologic novelty. Later, paleontologists, from Simpson to Gould, Stanley, and others, accepted the primacy of natural selection but argued that rapid speciation produced a discontinuity between micro‐ and macroevolution. This second phase emphasizes the sorting of innovations between species. Other discontinuities appear in the persistence of trends (differential success of species within clades), including species sorting, in the differential success between clades and in the origination and establishment of evolutionary novelties. These discontinuities impose a hierarchical structure to evolution and discredit any smooth extrapolation from allelic substitution to large‐scale evolutionary patterns.

Paper open access here – note the title:

https://onlinelibrary.wiley.com/doi/full/10.1046/j.1525-142x.2000.00045.x

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Then please show me a single genetic difference between humans and other ape species that could not be produced by a microevolutionary event.

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Take it up with Doug Erwin. I’m a bystander, offering other EVOLUTIONARY perspectives for JeffB.

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Your inability to answer the question will do.

The evolutionary perspective is that the differences between the genomes of different species is due to the accumulation of singular mutational events. Which mutations make it into modern species is the result of natural selection and population genetics.

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No – you asked a silly question.

What is the genetic basis of language, comparing chimps and humans? If microevolutionary changes suffice to explain the species-level differences, show us where, in the Pan and Homo complete genomes, respectively, the relevant basepairs are.

For that matter, what is the genetic basis of colored versus white sclera?

I asked Josh the latter question when we first began corresponding, one-on-one, several years ago. He didn’t know then, and he doesn’t know now. Nobody does.

So color me underwhelmed by human and chimp genetic similarity, when the differences between the species are what common descent claims to explain. Take some insight from Jonathan Marks:

It is not that difficult to tell a human from an ape, after all. The human is the one walking, talking, sweating, praying, building, reading, trading, crying, dancing, writing, cooking, joking, working, decorating, shaving, driving a car, or playing football. Quite literally, from the top of our head (where the hair is continually growing, unlike gorillas) to the tips of our toes (the stoutest of which is non-opposable), one can tell the human part from the ape part quite readily if one knows what to look for. Our eye-whites, small canine teeth, evaporative heat loss, short arms and long legs, breasts, knees, and of course, our cognitive communication abilities and the productive anatomies of our tongue and throat are all dead giveaways. However, they are not readily apparent in a genetic comparison.

Jonathan Marks, “What is the viewpoint of hemoglobin, and does it matter?” Hist. Phil. Life Sciences 31 (2009):241-262; p. 246.

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You are now going off on your own and can’t appeal to Doug Erwin. Is it your contention that the differences between Pan and Homo are not genetic? If not, what do you suppose they are? Just because we can’t now point to the genetic basis of a function is not evidence that it has no such basis.

This isn’t true. Common descent — inheritance — explains the similarities only. The differences are explained by various processes of divergence, notably mutation, selection, and drift. You are proceeding from a false understanding.

I ask again, is it your contention that the important differences between humans and chimps do not have a genetic basis?

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That isn’t Erwin’s point. He’s talking about species selection (though he uses the term “species sorting”). Species selection involves no genetic changes in populations, just changes in the frequency of genotypes within the biota. It conceivably explains why we now have Homo sapiens rather than Homo neanderthalensis or Homo ergaster. It doesn’t explain why those species have (or had) the genomes they do (or did).

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Not relevant to what @T_aquaticus is talking about, which is the genetic, evolutionary transformation of an ancestral population into the descendant one. Nothing in what you quote says that such genetic transformations don’t take place by the accumulation of mutations under selection and drift.

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This is irrelevant to the discussion.

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Think about this carefully. It is false.

The mutations – approximately 50-100 single-nucleotide polymorphisms – in any human genome, when compared to its paternal / maternal genomes, occurred in the parental gamete-forming cells. Those mutations are inherited, via descent with modification. Similarities AND differences are inherited.

About your question. Telling me that the phenotypic (character presence) difference between humans and chimps, “speech / no speech” has a genetic basis, only you don’t know where it is, leaves me wondering about the evidential grounds of “has a genetic basis.” You want me to show you something, but you should show me.

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Pot meet kettle.

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This statement needs to be challenged and scrutinized. Is it true? Or is it made up for the convenience of argument? Where in the evolutionary literature can this statement be vetted?

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You have succeeded in confusing cell generations with organismal generations. That’s all. We generally consider mutations that happened in the gametes that combined to form you as your mutations, not your parents’. Nor does this have anything to do with the Marks quote or your contention about the differences between species. You are throwing out a cloud of squid ink.

I presume, then, that you doubt the genetic basis of speech and yet have no alternative to suggest. Why so coy? Is it because you think that the seat of speech is the soul, and you’re too embarrassed to bring up that topic?

Now, why do I think that genetics is behind this and other differences between humans and chimps? Because they’re inherited and, beyond a few uninteresting exceptions inheritance is genetic.

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Go ahead. It’s elementary reasoning from the nature of descent with modification. See if you can handle it. You and I are the same in many ways, some of which is explicable as resulting from inheritance from a common ancestor. You and I are different in many ways too. Is any of that explicable as resulting from inheritance from a common ancestor?

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Do you believe there is no genetic difference responsible for the colour of the sclera? If you’re trying to make a point about human exceptionalism, that particular example seems like a silly place to start.

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As Sean Carroll reminded us:

Evolution of homeotic genes and the traits they control has been very important, but has not occurred by different means than the sorts of mutations and variation that typically arise in populations. The preservation of Hox genes and other tool kit genes for more than 500 million years illustrates that the pressure to maintain these proteins has generally been as great as that upon any class of molecules. Instead, the evolutionary tinkering of switches, from those of master Hox genes to those of humble pigmentation enzymes, typically underlies the evolution of form. The continuity of the tool kit and the continuity of structures throughout this vast time illustrate that we need not invoke very rare or special mechanisms to explain large-scale change. The extrapolation from small-scale variation to large-scale evolution is well justified. In evolutionary parlance, Evo Devo reveals that macroevolution is the product of microevolution writ large.

Works for plants as well…

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If that used to be an example of human exceptionalism, then it has been knocked down.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.researchgate.net/publication/274642518_Gorillas_with_white_sclera_A_naturally_occurring_variation_in_a_morphological_trait_linked_to_social_cognitive_functions&ved=2ahUKEwiO09D7vcnuAhXASjABHZbzDN8QFjARegQIExAB&usg=AOvVaw0HuDiR9OXCPNVHj_Z_Eg00&cshid=1612210099496

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The ability to use language and speech is in the genetic differences between our genomes.

Again, the sequence differences between our genomes.

Common descent explains the similarities. Mutations explain the differences.

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I am aware of what Erwin was discussing, so I apologize if I didn’t make that plain. I tried to include them in this sentence:

“Which mutations make it into modern species is the result of natural selection and population genetics.”

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Well, not exactly clear. Species selection is usually considered to be neither natural selection nor population genetics.