I just got back to the States from the Republic of Georgia two nights ago; I’d thought I wasn’t really feeling the effects of the 8-hour time difference, but here I am at 6:00 a.m. feeling as fresh and sprightly as an antelope. Well, almost as much as an antelope. I didn’t have the chance to update the blog while I was in Georgia, so I’ll jot down some thoughts about my experience overall.
Tomorrow I head out the Republic of Georgia, where I’ll be helping at the Dmanisi Paleoanthropology Field School. The site is pretty important for human origins. It is the earliest hominid site outside of Africa (~1.77 million years ago), and so helps document the earliest periods when humans first became a colonizing species. There are a number of fairly complete skulls and a few partial skeletons. What we see in the cranial and mandibular remains is a great deal of morphological variation; however, it is very possible that this fossil assemblage samples a single population. This is important to take into account since many anthropologists are quick to use subtle variations to argue for the presence of multiple species. Also, researchers from a number of countries have come together to work at this exciting site.
Some fun new things in anthropology of late. For starters, friend and colleague Adam Van Arsdale co-authored a paper recently released in Journal of Human Evolution about variation in the Dmanisi mandibles <!–[if supportFields]> ADDIN EN.CITE Rightmire19819817Rightmire, G. PhilipVan Arsdale, Adam P.Lordkipanidze, DavidVariation in the mandibles from Dmanisi, GeorgiaJournal of Human EvolutionJournal of Human EvolutionIn Press, Corrected ProofSystematicsRandom resamplingDimorphismPeriodontal diseaseSpeciesHomo erectushttp://www.sciencedirect.com/science/article/B6WJS-4S9R84K-2/1/805607b801be11bd456682d5a01816b2 <![endif]–>(Rightmire et al.)<!–[if supportFields]><![endif]–>. Dmanisi, in the Republic of Georgia and dating to about 1.77 mya, is interesting because the human fossils (Homo erectus) there represent the earliest definite excursions of hominins outside of Africa. Also interesting is the fact that the assemblage very likely represents a “paleodeme,” i.e. an actual living population. It was recently reported <!–[if supportFields]> ADDIN EN.CITE de Lumley200815015017de Lumley, Marie-AntoinetteBardintzeff, Jacques-MarieBienvenu, PhilippeBilcot, Jean-BaptisteFlamenbaum, GuyGuy, ChristopheJullien, Michelde Lumley, HenryNabot, Jean-PhilippePerrenoud, ChristianProvitina, OlivierTourasse, MartineImpact probable du volcanisme sur le décès des Hominidés de DmanissiComptes Rendus PalevolComptes Rendus Palevol61-7971DmanissiGéorgieHomo georgicusÉruption volcaniqueTéphrasÉtiologie des décèsVictimes du volcanismeDmanisiGeorgiaHomo georgicusVolcanic eruptionTephrasDeath aetiologyVictims of volcanism2008http://www.sciencedirect.com/science/article/B6X1G-4RR8D7V-1/1/015a368361815b7255927993ac9444a7 <![endif]–>(de Lumley et al. 2008)<!–[if supportFields]><![endif]–> that the Dmanisi hominins were probably a single group that was trapped quickly in a volcanic catastrophe—bad for them, good for paleontologists. So, Philip Rightmire, our friend Adam and David Lordkipandize have written a paper in response to an earlier paper suggesting that the size variation in the Dmanisi mandibles was so great that it represents more than one taxon. Rightmire and colleagues demonstrated, I think convincingly, that much of this ‘dimorphism’ is likely the result of taphonomic (the D2100 mandible is broken inferiorly), pathological and ontogenetic factors (the D2600 mandible is huge, possibly due to its advanced age and “pathology associated with dental wear”). So Dmanisi is pretty sweet: very early Homo all the way out in Georgia at least 1.7 mya, and we have a good collection of what probably represents not just a single, dimorphic species, but an actual (sub)population. Kudos, Adam!
What else…Oh yes! Another recent study suggests that vertical climbing costs the same energy per unit of body-weight in primates <!–[if supportFields]> ADDIN EN.CITE Hanna200820420417Hanna, Jandy B.Schmitt, DanielGriffin, Timothy M.The Energetic Cost of Climbing in PrimatesScienceScienceScience898-32058782008May 16, 2008http://www.sciencemag.org/cgi/content/abstract/320/5878/898 10.1126/science.1155504<![endif]–>(Hanna et al. 2008)<!–[if supportFields]><![endif]–>. Jandy Hanna (no—apparently it’s not a pseudonym) and team MacGyvered a vertical climbing treadmill that also recorded energy expenditure (they had more than just a coat hanger, hock of Silly Putty and a tube sock), and subjected some small-bodied primates to some bouts of vertical climbing (man, anthropology can be sweet). They somehow also included humans in this study, but I’m not exactly clear on how yet, maybe I’ll consult their Supporting Material and get back to you on that. Anyway, they found that across the body sizes (from .17 kg to 1.4 kg) vertical climbing efficiency is more or less equal; humans fall within the confidence limits. Which is cool because as primates increase in body size they become more efficient at walking. This is because increased body size is associated with longer legs, requiring less muscle activity to keep moving. What does this mean? This suggests to the authors that the very earliest primates (Back to the Eocene) were probably very, very small-bodied, and this small size allowed them to move into a vertical-climbing niche with little to no energetic cost. It would be really interesting to see this study performed on more primate taxa, especially larger body sizes, maybe comparing monkeys to apes.
Finally, apparently the verdict is in: “Great Apes prefer cooked food” <!–[if supportFields]> ADDIN EN.CITE Wobber20320317Wobber, VictoriaHare, BrianWrangham, RichardGreat apes prefer cooked foodJournal of Human EvolutionJournal of Human EvolutionIn Press, Corrected ProofCookingDietHominid evolutionTubersMeathttp://www.sciencedirect.com/science/article/B6WJS-4SHN0B6-1/1/682f7743b00dd6a621c64bf00467be64 <![endif]–>(Wobber et al.)<!–[if supportFields]><![endif]–>. I could have told you that, I mean think: a delicious medium steak vs. crappy, uncooked, parasite-teeming jungle fruit? The point was to test the hypothesis that food preparation in the form of cooking probably occurred and was widely accepted quickly after hominins garnered control of fire. Richard Wrangham (3rd author on the paper) has been into the idea that cooked food was superlatively important in the course of human evolution (see “Out of the Pan and into the fire” in Tree of Origin, edited by Franz de Waal (2001)), and I suppose here he set out to examine the issue scientifically. I’m not terribly informed about or interested in this issue, though it is a bit neat. Basically they went to the Yerkes primate research facility in Hottlanta and the Leipzig Zoo and gave chimps, bonobos, gorillas, and orangutans free-will choices between raw and cooked tubers processed various ways. Most of the time the cooked tuber (or apples or beef, in some cases) was selected, and eureka there’s proof that early hominins had this inherent preference for something about cooked food, appeasing the Chef Boyardee inside them. They end with, “Overall, our findings conform to evidence that wild chimpanzees choose seeds that have been heated by wild fires (Brewer, 1978), demonstrating that great apes possess a preference for cooked items” (Wobber et al., in press). Well, maybe. I think cooked seeds are a bit different from cooked tubers and meat. Plus, these tests were all conducted on captive apes, many of whom had eaten cooked food before, sometimes regularly. I know it’s less feasible, but it would be more convincing if somehow wild apes could have been tested with foods they’d be most likely to encounter in the wild.
What the paper didn’t address, and which I think is much more interesting, is how (and when) exactly these early hominins would have cooked food. Bear with me. So you’re a hominin with fire—did you make it or did you find it naturally somehow?—and you know that it’s super effing hot, it can harden sticks, it scares away some predators, and that generally when things go into it they don’t come out of it. Why the hell would you throw your hard-earned food into it? Perhaps the earliest chefs noticed that wild-fire heated foods (cf. the chimps, above) were preferable to raw ones, for whatever reason, and maybe they started trying it with multiple foods. Ok, but how did they cook? In Wobber et al.’s experiment the tubers were oven-baked, but I don’t think they had Kenmore ovens in the Pleistocene. I don’t know, maybe I’m over-thinking this (I usually do), but I think what’s much more interesting, and admittedly more difficult to find out and test, is how the earliest cooking would have been done. Honestly I thought this paper was a bit silly. I mean if you want to go to the zoo, you don’t have to come up with an experiment. The Lincoln Park Zoo in Chicago is free—and they have a one-armed gibbon that is super sweet.
Anyway, that’s the news hereabouts. Oh, Jerry De Silva just successfully defended his PhD dissertation, and his talk was really cool and informative (it was about climbing and feet, and you know how I love climbing). This Wednesday Robin Nelson will be defending her dissertation, and although I’m no psychic, no Johnny Carson, I’m pretty confident that her talk will be interesting and that she will defend successfully. So congratulations to Jerry and (prematurely) to Robin! Oh, and Kristen got a job and her research grant, so Kudos to her, too. And I’m gonna run my first half-marathon in a week and a half. Sweet.
<!–[if supportFields]> ADDIN EN.REFLIST <![endif]–>de Lumley M-A, Bardintzeff J-M, Bienvenu P, Bilcot J-B, Flamenbaum G, Guy C, Jullien M, de Lumley H, Nabot J-P, Perrenoud C, Provitina O, Tourasse M (2008) Impact probable du volcanisme sur le décès des Hominidés de Dmanissi. Comptes Rendus Palevol 7(1):61-79
Hanna JB, Schmitt D, Griffin TM (2008) The Energetic Cost of Climbing in Primates. Science 320(5878):898-
Rightmire GP, Van Arsdale AP, Lordkipanidze D Variation in the mandibles from Dmanisi, Georgia. Journal of Human Evolution In Press, Corrected Proof
Wobber V, Hare B, Wrangham R Great apes prefer cooked food. Journal of Human Evolution In Press, Corrected Proof<!–[if supportFields]><![endif]–>