Neandertals have long been touted as a species with “hyperarctic” adaptations. Their stout proportions and shortened distal limb segments are often explained to conserve heat. Similarly, the Neandertal cranium is traditionally said to be cold adapted. An article released on December 22nd in the Journal of Human Evolution challenges these traditional notions, specifically those about Neandertal nasal adaptations.
The Neandertal nasal apparatus has conventionally been cited as cold adapted mainly because of the enlarged sinuses. The authors of this article, among them Chris Stringer, cite evidence that larger sinuses are not in fact typical of cold weather mammalian species.
Through observation of human populations and studies on other mammals, cold weather is more highly correlated with smaller sinuses. That is, animals from more northerly locations typically have smaller sinus cavities. As an example taken from lab studies, rats raised in colder conditions also show smaller sinus cavities.
But are Neandertal sinuses even large, as is typically maintained? The authors of this paper argue that there is nothing large about them. Through examination of Neandertal remains, the sizes of the frontal and maxillary sinuses actually fell within the range of Homo sapiens from temperate climates.
This study is very suggestive that Neandertal nasal anatomy is not due to cold weather adaptation. To be cold weather adapted, the sinuses would be smaller and not larger, as many anthropologists have maintained since the first remains were discovered. Not only are the sinuses not small, they are not large- which speaks to a larger problem. How many other basic assumptions do we take as fact just because they have been around for so long?
If not cold weather, what could have caused the differences in facial anatomy between H. neanderthalensis and H. sapiens? The authors of this paper do not offer many answers, but offer a couple of possibilities. Differences in masticatory stress (utilizing teeth as a tool, for example), or genetic drift are two potential reasons discussed.
This paper may be taking another step in overturning traditional understanding of Neandertals as a cold weather species. Generations of anthropologists have passed knowing that Neandertals differed in facial anatomy due to cold weather adaptation, unsubstantiated by data.
Rae, T.C., Koppe, T., Stringer, C.B. (2010). The Neanderthal face is not cold adapted. The Journal of Human Evolution. Article in Press.