Meat-eating, porotic hyperostosis and early Homo

A large group of researchers working at Olduvai Gorge, including Manuel Domínguez-Rodrigo (IDEA, Madrid), Charles Musiba (UC-Denver) and Henry Bunn (U. Wisconsin), have a paper out in PLOS One this week on evidence of porotic hyperostosis in a 1.5 million year old juvenile from Olduvai. The paper happens to coincide perfectly with the pathology unit in my Forensic Anthropology class, which is wonderful.

As might be expected, much of the paper is focused on the positive identification of porotic hyperostosis in the specimen and its specific association with anemia. The bones of the skull have a natural porosity, porosity that could easily be altered by the process of fossilization and subsequent preservation through time. The authors provide a nice case for how the specific porosity observed in OH81–situated pericranially on the parietal and expressed primarily by a loss of the outer table of cortical bone–is consistent with porotic hyperostosis (though I would like to have seen a clearer indication of the exact stratigraphic position of the specimen with respect to potential diagenetic modification).

The authors then link the observation of porotic hyperostosis specifically to megaloblastic anemia:

Together, these observations suggest that if OH 81 was still nursing at the onset of anemia, then his/her mother’s diet was deficient in animal product. Alternatively, if OH 81 was being weaned at the onset of anemia, then it was the meat component of his own diet that was inadequate. The nutritional stress caused by weaning can lead to megaloblastic anemia, which frequently, in conjunction with gastrointestinal infections, produces diploic marrow hypertrophy, resulting in the ectocranial exposure of diploic trabeculae, typical of porotic hyperostosis [2].

If their diagnosis of porotic hyperostosis is correct, this is clearly evidence of a nutritionally-stressed and/or infection-laden young child (the two tend to co-occur in more complete skeletal samples – see Mensofrth, Lovejoy, Lallo & Armelagos, 1978).

Where I get confused is when the accompanying Science Daily headline says, “Eating meat may have made us human.” I happen to be in the camp that sees the origin of Homo (or maybe Homo erectus, more specifically) as part of an ecological shift within the lineage that includes a greater utilization of animal-based fats and proteins. So I am predisposed to seeing meat as important, but it is only one part of the ecological and physiological shift observed in early Homo. I have a harder time seeing this specimen as specifically indicating that a lack of meat was the de facto cause of the poor health in OH 81. This is one of the challenges of drawing broader conclusions from pathological specimens in the paleo-record. As the authors of the PLOS paper themselves conclude:

Because fossils of very young hominin children are so rare in the early Pleistocene fossil record of East Africa, the occurrence of porotic hyperostosis on one, OH 81, suggests we have only scratched the surface in our understanding of nutrition and health in ancestral populations of the deep past.

Having just scratched the surface, it is hard to expand this observation into a broader argument. I would say that rather than indicating “meat eating made us human,” this specimen is consistent with the idea that early Homo had a nutritional childhood disease profile that potentially overlaps with recent humans, with the previous absence of evidence of this kind of pathology no longer a viable point of argumentation.

This is similar to some discussions about the edentulous skull from Dmanisi, D3444, and the possibility of human social care in the Lower Pleistocene. This was a specimen that was largely, if not entirely, edentulous for an extended period of time prior to its death. Some have suggested that this is an indication of social care, as it is hard to survive in the world without teeth to serve as primary processors of food (see here, for an example of this argument). What it really demonstrates is that the range of possible explanations includes, but does not necessitate, a human-like scenario of social care going back 1.8 million years. It is hard to argue from a sample size of one, as is the case with both OH 81 and Dmanisi 3444. In the case of Dmanisi, you have to go ~1.7 million years forward in time to find the closest equivalent specimen, a Neandertal from the French site of La Chapelle-aux-Saints. For more discussion on the case of the Dmanisi specimen, check out this old post from John Hawks on the topic.

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1. Domínguez-Rodrigo M, Pickering TR, Diez-Martín F, Mabulla A, Musiba C, et al. (2012) Earliest Porotic Hyperostosis on a 1.5-Million-Year-Old Hominin, Olduvai Gorge, Tanzania. PLoS ONE 7(10): e46414. doi:10.1371/journal.pone.0046414