morphological integration

New decade, new syllabi

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We just kicked off the Spring semester here at Vassar College, and so I’ve got some freshly-updated bio-anthro syllabi hot off the press. This semester, I’m doing my annual introductory class (Anth 120, “Human Origins”), a resurrected seminar (Anth 305: “Human Evo-Devo”), and a second stab at a new methods module (Anth 211: “Virtual Anthropology”).

Anth 120 is similar to previous versions, although this year I’ve taken out a reading/lecture on Paleolithic technology, replaced with articles scrutinizing evolutionary psychology. We’ll see how it goes.

The other two classes are greatly overhauled from previous versions. Anth 211, “Virtual Anthropology,” is my first contribution to a new curricular initiative here at Vassar, which are called “intensives.” Anth 211 is kind of a hybrid between a regular class and an independent study, giving students experience with computer-based, “virtual” methods used in biological anthropology and related fields.  In the first half of the semester, students will get to try out some of these methods and see what kinds of research questions they’re used for. In the 2nd half of the term, students do their own Virtual Anthropology study drawing on the materials in my HEAD Lab, and then present a research poster at the end of the year. I debuted this intensive last Fall, and based on that experience I’m providing a bit more training and have more activities for students this Spring. If last semester’s projects are at all predictive, we should have some fun projects in store this year.

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Anth 305 is a fossil-focused examination of the roles of growth and development in human evolution, and this year’s version is also highly modified from the last time I taught it over two years ago. In that first version, course content was patterned along the skeleton, e.g., one week looked at evolution and development of teeth, next week the spine, etc. Such a bauplan might work for building bodies, but it wasn’t the best for teaching. So this year, we’re spending the first few weeks on the fossil record of human evolution, getting acquainted with the curious characters of our deep past. From there, we go over skeletal / developmental biology, before delving into special evo-devo topics like “morphological integration” and “heterochrony” for the rest of the semester. We’ll also read lots of old, “classic” papers along the way.

Syllabi for these, and other classes, can be found on the teaching page of the site, if you want to learn more.

Is Boas Dead?! Anthropology graduate conference

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The University of Michigan’s Anthropology graduate association (MAGA) is hosting a FREE anthropology conference here in Ann Arbor this coming Saturday, 27 March. The event is titled, “Is Boas Dead?! Four-field anthropology in the 21st Century,” (click the title for the link) and will feature a day of anthropology talks in all four fields (well, archaeology didn’t really represent, unfortunately).

Four members of this blog will be presenting at this conference. I myself will be presenting at the end of the day, in a talk fairly mundanely titled, “Population-specific variation in studies of integration.” Basically, variation is a natural part of human populations. However, some populations are more variable than others. The question I ask is whether variation unique to populations poses a problem for studies of integration, which are based on correlations between traits, usually in large, pooled samples containing individuals from all over dodge. The answer to the question is, ‘yes and no.’
So if you can make it out, come see what the Michigan anthropology graduate students are up to! It’s free, and better yet, educational! Or maybe the free part is more exciting.

Evolution of human fingers and toes: The two go foot in hand

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A really cool study was just published in the journal Evolution, and what with getting my apartment ready for a New Year’s party on the 31st, and my being completely incapacitated yesterday, I didn’t get to read through it until today. Campbell Rolian and colleagues (in press) address the question: In human evolution, were hand and foot digital proportions each the targets of direct selection, or could hand/foot proportions have evolved as a byproduct of selection on only the hand or only the foot?

This is an interesting question. In your standard Anthropology 101 class, you learn about how humans (and hominins) are unique relative to apes. Two unique things about us are: a robust, adducted big toe for bipedalsim, and a hand adapted for tasks requiring a fairly high degree of dexterity, such as tool use. But something to keep in mind–indeed the authors of this study did–is that the hand and foot are serially homologous, each is a variant on a common theme. Because the developmental architecture behind the hand and foot are largely similar, an intuitive question is whether selection on the hand or foot only would effect the evolution of the element that wasn’t under selection. Could developmental integration of the hominin hand and foot have led to evolutionary integration, do/did the hand and foot co-evolve?

Turns out this may well be the case. Authors looked at lengths and widths of hand and foot phalanges (finger bones) in a sample of humans and chimpanzees. Generally, in both Pan and Homo, homologous traits in the hand and foot are more highly correlated than expected by chance, even compared to correlations between traits within the hand and foot. Cool, and none too unexpected.

But then the authors did some crazy simulations, to see what kinds of selection regimes on the hand and foot may have led from a chimp-like morphology to the morphology we humans enjoy today. I’ll need to reread this section a couple times, but it looks like selection on the big toe is one of the most important aspects of hominin hand/foot evolution. And it would not be impossible for evolutionary changes in the human hand to be largely by-products of selection on the foot, due to the nature of covariation (integration) of the hand and foot. Whoa!

The implication, which the authors seem to like, is this: given a chimp-like ancestral morphology for the hand and foot, it seems that the two major hominin/human traits given above (bipedalism and tool-use/manual dexterity) are largely due to selection simply on the foot. That is, because of the developmental integration of the hand and foot, selection for a bipedally capable foot indirectly induced the evolution of a hand conducive to manipulation. Ha, the hand was just along for the ride! Get it, because the feet move the body, and so the hand… but also evolutionarily… Dammit.

Anyway, that’s nuts! Of course, another very interesting thing about the first digits of the human hand and foot, aside from the fact that the first digit on both is relatively large and robust, is that the mobility of these digits is just about opposite what it is in the apes. Whereas the big toe is very mobile/opposable in apes (and the 4.4 million year hold putative hominin, Ardipithecus ramidus), it is completely adducted in humans (and fossil hominins that aren’t Ar. ramidus). Less extreme, the human thumb joint is allegedly more mobile than apes’ thumbs. So this is the next step, I guess: what is the developmental basis for the wild evolution of the human hallux and pollex joints?

Reference
Rolian C, Lieberman DE, and Hallgrimsson B. Coevolution of human hands and feet. Evolution: in press.

Summer Research

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I’ve been pretty busy since classes let out, so it’s been a while since I’ve posted anything. Two years of grad school down, n more to go. Hopefully no more than four more….

In a few hours, I leave lovely Ann Arbor, MI for my summer research, to the Transvaal Museum in Pretoria, South Africa. So far as I can tell, this museum has good collections of cultural artifacts, recent mammals, and tons of fossils. Many hominin remains are curated here as well, namely Australopithecus from the region–A. africanus from Sterkfontein and Makapansgat, and A. robustus from Swartkrans, Kromdraai, and I think also maybe Cooper’s Cave(?).

I’ll be focusing on the A. robustus collection. As with many fossil groups, the sample is largely teeth, and most other cranial remains are highly fragmentary–there are only a few relatively complete crania (including a remarkably well preserved skull, DNH 7 from Drimolen, which I don’t think is at the Transvaal and that I doubt I’ll get to examine. Oh well). The main project will examine the relative independence of many of the cranial, facial, and dental features in A. robustus, since these have been important in debates about whether the A. robustus and A. boisei (the latter from E. Africa) are more closely related to one another than to other hominins. Basically I’m going to test a few developmental/functional models that have been proposed, by applying a resampling procedure (that I’m still sort of in the process of developing). Hopefully it will be an interesting (and successful…) way of examining morphological integration in a fossil sample.

There are a few other projects, but this is the one I’m most interested in. I’ll do my best to keep Lawnchair readers (whoever they might be) updated. Here’s to what I hope will be a productive summer!