Dmanisi Homo erectus: I’ll have what she’s having

Speaking of diet in fossil humans … Herman Pontzer and buddies just published a brief analysis of fine-scale tooth wear in the Dmanisi Homo erectus specimens.

Source: http://bit.ly/uD1LWo

Teeth are useful as hell in life. Humans’ teeth are critical not only for eating, sporting a sexy smile, and biting people (right), but also for speech and song (“f,” “th” and “v” sounds). Some parents even harvest their childrens’ exfoliated baby teeth. The things we do with teeth.

Teeth are also really useful for studying long-dead people and animals – teeth may preserve pretty well for millions of years, they can be used to estimate an individual’s age-at-death, and their shape and composition can be used to learn about diet. In a vile act of revenge, the food that sustains us also scrawls its Nom Hancock into the surfaces of our teeth. So, scientists can study the microscopic marks (= “microwear”) on tooth surfaces to see what kinds of foods were eaten shortly before death. Peter Ungar, an author of the current paper, has done a lot of work here, and his website is worth checking out if you’re interested in learning more. Microwear can’t really tell you exactly what an animal was eating, but can tell you whether the animal mostly ate grasses, leaves, hard objects like nuts, and so forth.

So Pontzer and colleagues (in press) examined the microwear on some of the lower molars of the youngest members of the nearly 1.8 million year old (Ferring et al. 2011) Homo erectus group from Dmanisi in the Republic of Georgia. To the left is a picture of the jaws, from the paper (from another paper. How meta of me). The microwear patterns of these badass early humans fit cozily within the variation exhibited by other Homo erectus specimens.

Microwear in Homo erectus is pretty variable, but still rather distinct from other fossil groups like robust Australopithecus, and a little less distinct from their putative ancestor H. habilis. This suggests that something special about Homo erectus was the species’ great dietary breadth – Homo erectus‘ key to colonial and evolutionary success might not have been the adoption of a key dietary resource, but rather the ability to utilize a wide range of food resources. Atkins diet be damned. What’s neat is that the Dmanisi hominids, though kind of primitive (Australopithecus-like) in terms of brain size and some aspects of skull shape, nevertheless demonstrated key behaviors of H. erectus, namely colonization (Dmanisi is the oldest reliably-dated hominid site outside Africa), and dietary flexibility. This really suggests the success of our ancestors was due to some behavioral innovation, aside from advances in stone tool technology.

Source: http://bit.ly/vCTfeR

Now, these Dmanisi H. erectus kids’ teeth wore like other H. erectus, and it would be reasonable to infer that this is because they ate similar foods. This makes it all the more mysterious that the other Dmanisi jaws, from older adults, have teeth completely worn to shit (sorry to swear). D3444/3900 (left) are the cranium/mandible of an individual who was missing all their teeth, except maybe a lower canine – the earliest example of edentulism in the human fossil record (Lordkipanidze et al. 2005). D2600 (below) is a very large mandible with teeth so worn that the pearly-white first-molar crowns were gone and the internal pulp cavity (and nerve) were exposed. (Interestingly, D2600 is so large that some researchers initially argued it represented a different species from the other jaws – yet Adam Van Arsdale presented evidence that this extreme tooth wear may actually be responsible for making jaws relatively taller in early humans).

Source: http://bit.ly/u6bk6h
So what’s curious is why the older Dmanisi hominids should show such an extreme amount of tooth wear compared to other H. erectus, but microwear on the young suggests their diet was the same (that is, just as diverse in texture) as others in the species. Was Dmanisi-level tooth wear (and tooth loss) comparable to other H. erectus, and we just happen not to have found them at other sites? (KNM-ER 730 from Kenya is the next-most worn early Homo that next comes to mind) Is there another aspect of diet we don’t know about, that caused the Dmanisi teeth to wear especially quickly? Or were these early Homo from Dmanisi actually living longer than other H. erectus? I suspect the second is more likely, but that’s a hypothesis that remains to be tested.
ResearchBlogging.org
Read more, dammit!
Ferring, R., Oms, O., Agusti, J., Berna, F., Nioradze, M., Shelia, T., Tappen, M., Vekua, A., Zhvania, D., & Lordkipanidze, D. (2011). From the Cover: Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85-1.78 Ma Proceedings of the National Academy of Sciences, 108 (26), 10432-10436 DOI: 10.1073/pnas.1106638108
Lordkipanidze, D., Vekua, A., Ferring, R., Rightmire, G., Agusti, J., Kiladze, G., Mouskhelishvili, A., Nioradze, M., de León, M., Tappen, M., & Zollikofer, C. (2005). Anthropology:  The earliest toothless hominin skull Nature, 434 (7034), 717-718 DOI: 10.1038/434717b
Pontzer H, Scott JR, Lordkipanidze D, Ungar PS. In press. Dental microwear texture analysis and diet in the Dmanisi hominins, Journal of Human Evolution (2011). DOI:10.1016/j.jhevol.2011.08.006
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