School for Advanced Research, Santa Fe

Have you heard of the School for Advanced Research in Santa Fe? If not, I want to rectify that. From their “about” web page, it was established in 1907 “as a center for the study of the archaeology and ethnology of the American Southwest. Since 1967, the scope… has embraced a global perspective through programs to encourage advanced scholarship in anthropology and related social science disciplines and the humanities, and to facilitate the work of Native American scholars and artists.”

I was honored to take part in this mission in March of 2016 as a participant in the Advanced Seminar on Geospatial Approaches in Anthropology organized by Bob Anemone and Glen Conroy. I took part to share the satellite imagery-driven survey work Jackson Njau and I did in Tanzania, and other field work.

Photo from the SAR page about the seminar: http://sarweb.org/index.php?advanced_seminar_new_geospatial_approaches_in_anthropology-p:2016_seminars
Photo from the SAR page about the seminar: http://sarweb.org/index.php?advanced_seminar_new_geospatial_approaches_in_anthropology-p:2016_seminars

Ok, ok, I know some of you saw that photo and had the immediate reaction of “MAN-PANEL!” I get it. Men are starting to speak up and avoid events with such a crazy sex bias. But if you are the only woman, what do you do? Not go and let there be no representation? The composition of the group morphed a bit over the year in advance, so it wasn’t obvious until just before that it had become a man-panel. There are women who I could have suggested, but I didn’t notice early enough to speak up. I’ll pay more attention in the future.

But, I bring up the SAR seminar for a different reason.

See the guy standing behind me to the right? That’s Peter Ungar. He studies what he has dubbed “food prints”, which is a clever term that encompasses the scratches, pits, isotopes, and whatnot that food leaves on teeth. From this, he can figure out what long-extinct animals ate. It’s pretty neat work that you should check out, and maybe even buy one of his books!

Peter and I are, as you immediately see, both tooth biologists and have known each other since I was a graduate student. Over the last couple of years, we’ve talked for a few minutes as we’ve crossed paths at various conferences about why robust hominids have really robust teeth and what they used them for.

Background: There was a hominid living in eastern Africa and another living in southern Africa millions of years ago. They have huge molars and premolars, and very little incisors and canines. These features are associated with huge masticatory anatomy — the bones and muscle attachments of the jaws. We know they must have been eating an impressively difficult diet, but what was it? Did both species eat the same thing? Do they look similar because of shared ancestor or convergence?

From the “food prints”, it turns out that they were apparently eating different things. But, why would they have such similar shaped teeth if one of them was eating moreso leaves than the other?

The work I do brings a consideration of the underlying genetics to solving this conundrum.

From the developmental genetics research done on mice, lots of genes are involved in making cusps and configuring their placement on a molar. It is a complicated mechanism, and we scientists are still figuring it out.

In contrast, all of the genetics resarch to date suggests that the genetic mechanisms that influence whether or not a primate has thick or thin enamel is pretty simple. For example, my colleagues and I figured out that variation in molar enamel thickness doesn’t have any genetic correlation with tooth size or body size or anything else we could think of to test (see Hlusko et al. 2004 American Journal of Physical Anthropology “Genetics and evolution of primate enamel thickness: A baboon model”).  (By the way, that was an amazing paper to write — I should blog about that one of these days…)

Peter and I were pretty sure that these two huge-toothed hominid species look alike not because of adaptation to eating the same foods, but because of the underlying genetic architecture of dental variation. Both species had adapted to eating foods that were hard to process, although these were different types of foods. The simpler genetic architecture of enamel thickness in primates meant that thicker enamel could more readily evolve in response to the selective pressures of these more challenging diets. Pointy cusped teeth may be more ideal for eating leaves, but evolving them takes longer than does evolving thicker enamel because the underlying genetics is more complex.

And so, the first evolutionary response to these challenging diets were lineages with increasing enamel thickness. Had these creatures lived for millions more years, the leaf-eaters may have ultimately been selected to have pointy cusps good for leaf-eating.

What does this have to do with geospatial approaches in anthropology?

While we were both at the SAR seminar to talk about other aspects of our research, Peter and I got to delve into a much deeper conversation about genetic architecture and foodprints. A walk around Chaco Canyon solidified our ideas. We then skipped an afternoon walk around the beautiful SAR campus to sit at the wooden dining room table to sketch out the argument. We had a manuscript submitted within weeks, and just two days ago, our hypothesis was published as a Perspective (“Evolutionary Path of least resistance“) in Science.

This experience has reinforced to me the benefit of professional meetings, and especially, of the tremendous value in putting academics together for longer periods of time to contemplate and discuss. There are very few institutions that provide this kind of forum, and SAR is one of them. And, an important one at that. Thank you to the amazing SAR staff who made this possible, even though it is an off-shoot of the original intent of the seminar. The geospatial work is coming…

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