Wednesday, November 22, 2006

Neanderthal childhood was as long as that of modern humans

Picked this one up on the website of the Montréal daily La Presse. The story (in French) reports on a study by Christopher Dean (University College London) and colleagues from French and Italian institutions which shows, through the use of high-resolution microcomputed tomography on two molars, that childhood was of comparable duration for Neanderthals and modern humans. Digging around the Nature web site, I found the paper in question, by Macchiarelli et al. (2006) in the papers available in advance of press. The authors conclude that

"Our data now allow us to predict M1 emergence time in Neanderthals with more certainty. If about 8mm of root were formed at an average of about 5.7 mmper day at gingival emergence, then this would have occurred at about 6.7 years of age, well within the human range (6.260.8 years (mean 6 s.d.)). This, together with the modern human-like position of the neonatal line, suggests both similar timing of tooth initiation relative to birth in Neanderthals and modern humans, and a predictable extended period between birth and M1 emergence, by which time about 90% of brain volume would have been attained."

While they also mention that that "a more complex enamel–dentine junction morphology and a late peak in root extension rate sets [Neanderthals] apart", their results are in contrast to those previously reported by Fernando Ramirez Rozzi and José Maria Bermudez de Castro (2004) who estimated that Neanderthals reached adulthood around fifteen years of age or so, that is to say, significantly earlier than modern humans. I should note that the Ramirez Rossi and Bermudez de Castro conclusions had already been challenged by Guatteli-Steinberg et al. (2005) who used dental perikymata counts to reocnstruct Neanderthal life history and show that it was similar to that of modern humans.

Macchiarelli et al.'s results provide another thread of evidence that demonstrates that modern humans and Neanderthals may not have been significantly different in terms of their biological development. This has a number of implications about the life history of Neanderthals, the structure of their population and the nature of their knowledge transmission strategies. This is especially interesting in light of a recent paper in the Journal of Human Evolution by Gurven et al. (2006) about the time needed to become a proficient hunter. Based on observations on the Tsimane foragers in the Bolivian Amazon, Gurven et al. suggest that physical maturity alone is not enough to ensure fully proficient hunting (an activity which requires much skill), and that full proficiency might only be attained about 10-20 years after reaching adulthood.

Gurven et al. (2006) therefore do away with the idea that physical maturity is, by itself, sufficient to be a fully proficient hunter. Bocherens et al. (2001, 2005) suggest that at least some Neanderthals were top carnivores, which implies they were able to develop fully competent hunting capacities comparable to those of modern humans (if not actually better ones). The idea that Neanderthals could achieve this level of skill simply by maturing more quickly is therefore seriously undermined by the Gurven et al. (2006) paper, and the new Macchiarelli et al. study suggests that, in fact, there is no need to invoke such improbable scenarios to explain effective hunting among Neanderthals. Now, how this all fits with the debate over Neanderthal longevity and life-history as a whole is another debate, one which I will not broach today...

I have to say that also really love the reconstruction of Neanderthal adult-infant interaction depicted in the La Presse feature, and I had not seen before...

I love how the Neanderthal kid looks kinda lost or detached in this one, but then again, I'd probably look like that myself if I was left alone with a guardian that looked as haggard as that adult Neanderthal!


Bocherens, H., M. Toussaint, D. Billiou, M. Patou-Mathis, D. Bonjean, M. Otte, and A. Mariotti. 2001. New isotopic evidence for dietary habits of Neandertals from Belgium. Journal of Human Evolution 40:497-505.

Bocherens, H., D. G. Drucker, D. Billiou, M. Patou-Mathis, and B. Vandermeersch. 2005. Isotopic evidence for diet and subsistence pattern of the Saint-Césaire I Neanderthal: review and use of a multi-source mixing model. Journal of Human Evolution 49:71-87.

Guatelli-Steinberg, D., D. J. Reid, T.A. Bishop, and C. S. Larsen. 2005. Anterior tooth growth periods in Neandertals were comparable to those of modern humans. PNAS 102:14197-14202

Gurven, M., H. Kaplan, and M.Gutierrez. 2006. How long does it take to become a proficient hunter? Implications for the evolution of extended development and long life span. Journal of Human Evolution 51:454-470.

Macchiarelli, R., L. Bondioli, A. Debénath, A. Mazurier, J.-F. Tournepiche, W. Birch, and C. Dean. 2006. How Neanderthal molar teeth grew. Nature: doi:10.1038/nature05314

Ramirez Rossi, F.V., and J. M. Bermudez de Castro. 2004. Surprisingly rapid growth in Neanderthals. Nature 428:936-939.


Anonymous said...

Well, about all I can say is, I'm not surprised by this paper. Frankly, I don't understand why people cannot recognize that (relatively minor) anatomical differences between this prehistoric population and "modern" ones means or suggests gigantic behavioral ones. I'm writing a set of (related) science fiction novels that feature Neandertals. For background research, I've had to do a *lot* of reading of anthropological and other journals. And whenever anybody does any "fine grained" research on either things like Neandertal growth patterns or things like behavioral patterns, they tend to find very little, if any, difference between overall physiological patterns and/or behavioral patterns, from known, modern forager societies. This is just one ore piece of evidence suggesting this.
Anne Gilbert

Alexandre Steenhuyse said...

The Neandertal display is from the National Museum of Prehistory in Les Eyzies, France. isn't it? Love it!