Big trip 2011

It’s dawning on me now that I leave the country for the rest of the summer in just over 24 hours. First I’ll be in Pretoria for a few weeks studying Australopithecus robustus fossils at the Transvaal Museum. Then I’m off to Nairobi for a few days to check out some fossils at the Natural History Museum there. I’ve never been to Nairobi, and I’ll admit I’m a little nervous; I’ll keep you posted as to how it goes. Then right before my mum’s birthday I head to Tbilisi, Georgia for the 2nd annual Dmanisi Paleoanthropology Field School, until the end of August. Here’s a schematic of what my trip will look sorta like, starting from bottom to top.:
My whole life was up in the air for most of the first half of the year. But everything seems to have come together, so hopefully the second half of 2011 will be better than the first. That said, I don’t think I’m ready to go yet!
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Earliest human migrations

One of my favorite paleoanthropological sites is Dmanisi, in the Republic of Georgia. It is the oldest securely dated hominid site outside Africa (just under 1.85 million years ago), and the hominids found there display a neat mix of primitive Homo habilis and derived H. erectus features. I consider myself lucky to have had the opportunity to excavate at Dmanisi last year, and to return to Georgia (lamazi Sakartvelo! [I hope I translated that correctly]) for more fieldwork next month.
Recently, Reid Ferring and others (2011) described the results of excavations of M5, a section of the site a bit aways from the area where the hominids were found. M5 is pretty cool because it presents a nice geological “layer cake,” as Ferring described it to us: each of the strata (different layers of deposition) are nicely and evenly stacked on one another. Check out the labeled layers on the right of the figure, from Ferring et al. 2011:
This is in stark contrast to the jumbled strata (like ‘spaghetti’) where the hominids were found. In geology and archaeology, there is a general “law of superposition,” which states that the lowest layers in a sequence would have been deposited earlier than the layers above them. The A sediments at Dmanisi, as seen in the figure above, are thus older than the Bs. Hominids have only been found in the B sediments. But work at M5 has shown that stone tools are found in the older A sediments, meaning that hominids arrived at the site and used it continually, beginning just after 1.85 million years ago.
Tools from the site differ between the older A and slightly later (still older than 1.75 million years!) B sediments in both material and manufacture. As they say in the paper (p. 2/5), a major difference in tool manufacture between the strata A and B occupations could be that during the earlier A times, “either cores were more intensively reduced or selected flakes were made elsewhere and carried to the site.” I’m not sure why this may be, but it is neat that within a fairly narrow time span, researchers can see habits change in our early ancestors.
The authors also note that the older tools from A sediments indicate “that Eurasia was probably occupied before Homo erectus appears in the East African fossil record” (from the paper’s abstract). If only hominids also came out of the A sediments! The News is touting this as meaning H. erectus evolved in Eurasia and then some members of the ‘new species’ moved back into Africa, but I don’t think this is necessarily the case. The Dmanisi hominids are described as H. erectus, but lack some key H. erectus apomorphies (most notably a large brain size) and really look pretty similar to contemporary hominids in Kenya (such as KNM-ER 3733) and Tanzania (such as OH 16). Plus, the E. African hominid fossil record around 1.9 million years ago leaves some tantalizing hints at hominids more erectus-like than habilis-like, such as the ER 2598 occipital fragment.
So while Dmanisi definitely demonstrates the presence of hominids outside Africa earlier than most well-accepted “Homo erectus” (or “ergaster”) fossils in E. Africa, I don’t think they necessarily indicate that the species arose in Eurasia. Rather, what the fossil record likely shows is the evolution of populations of early Homo, in Africa and Eurasia, toward the more ‘advanced’ H. erectus we know and love (due to gene flow w/in a widespread species, rather than parallel evolution of similar traits in different species).
ResearchBlogging.org


Reference
Ferring R, Oms O, Agustí J, Berna F, Nioradze M, Shelia T, Tappen M, Vekua A, Zhvania D, & Lordkipanidze D (2011). Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85-1.78 Ma. Proceedings of the National Academy of Sciences of the United States of America PMID: 21646521

Dmanisi Field School: Success

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.

I had the good fortune to be able to assist a colleague in executing the first (annual) Dmanisi Paleoanthropology Field School. We had a brief field season (1 month) excavating the site of Dmanisi where the skulls and partial skeletons of several Homo erectus individuals have been found. In my previous post, I’d mentioned the site dated to around 1.77 million years ago. After being well-educated on the geology of the site by Reid Ferring, I can now say that the hominids are found between two basalts (lava flows) dating to 1.85 and 1.76 million years ago. Within these two basalt layers are A and B ashfall sediments. The A sediments are older, of normal magnetic polarity, indicating an age of 1.85-1.78 million years ago. The B sediments are reverse polarity, and were deposited between 1.78 – 1.76 million years ago. Stone tools are found through out the sequence, though Homo erectus is only known from B sediments. Enough about the geology.

Georgia itself is an amazing country. I really only spent time in the capital city of Tbilisi and the small town of Dmanisi [namely Patara (“little”) Dmanisi], and I’m sure that if I had the opportunity to see more I’d think the place is even more amazing. There is a very rich and ancient cultural heritage, and the country seems to be doing well for itself since the collapse of the Soviet Union. There’s an enduring Soviet influence, which for a simpleton like me means that there are amazing statues sprinkled about the place. Here’s a picture of the giant statue of Kartlis Deda (“Mother Georgia”), which overlooks the center of downtown Tbilisi. For a 20-meter tall woman, she was fairly difficult for me to find. Women…

The people I met and got to work with were great. The Georgians were super friendly and awesome. Here’s a picture of a lot of them (and me!) during the Paleolithic Games. This year it was only one game, using an atl-atl to hurl a spear at various targets. The top 3 winners were all named Giorgi; I only scored 2 points. Better luck next year. Anyway, I really like my newfound Georgian friends. In addition, I’m really glad to have met the other researchers and field school students. Everyone was super friendly and helpful and knowledgeable, and I think David Lordkipanidze, now head of the Georgian National Museums, has done a great job of integrating local Georgian and international researchers in the Dmanisi excavations. All in all, we really had a great crew.

It was a fossiliferous year, as it has been in the past, and will probably be in the future. Though we excavated for only a month, we uncovered a number of great fossils, including a complete hominid humerus that made the news (if I can find a non-facebook link again I’ll post the news coverage). Here’s a picture of the press interviewing Abesolam Vekua (left) and David Lordkipanidze at the site the last day I was there. Right where they are standing is where a number of hominid remains have come from. The humerus is from right behind where Vekua stands. He’s facing squares where we spent lots of time excavating, and that yielded some pretty interesting stuff; note the jumble of fossils to his left. I don’t know what I am and ain’t allowed to say, but suffice it to say that a number of cool things came out, many of which I’m sure you’ll be hearing about in the near future.
All in all, it was a great way to end this summer. I hope I have the opportunity to go back!

Outbound: Dmanisi, Georgia

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.

So what we have at Dmanisi are very early human ancestors, which point to a high level of intraspecific morphological variation. Hopefully this field school will recover something fun and interesting. I’m told we’ll have internet at the site, so I’ll try to keep the blog up to date on the goings on at the site.

May-stuffs

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.

References

<!–[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]–>