Day By Day

Thursday, October 22, 2009

Back to the Savanna?

The recent spectacular publication in Science of data on Ardipithecus has shaken up the field of evolutionary anthropology and forced reconsideration of what was considered to be settled scientific consensus [see discussion here]. The last time that happened was about fifteen years ago when palaeobotanists disproved the, to that point, universally accepted "savanna theory" which argued that human bipedalism and associated traits resulted from movement out of the forests and into grassland environments [here]. Now two studies are published that restore the savanna hypothesis to some, if not all, of its earlier prominence.

Artifacts found in southeast Kenya show that hominins were living in savanna environments 2 mya, long after the emergence of obligate bipeds but possibly before the development of many associated traits like hairlessness which might represent adaptations to the grasslands environment [here]. No sooner had this emerged than another team reported that close analysis of wear marks on Australopithicene teeth showed that grasses formed a large part of their diets [here]. That would seem to suggest that early bipeds inhabited an environment in which grass was common.

So we apparently cannot completely dismiss the possibility that much of what makes us different from other closely related species is due to life on the savanna after all. All the nice neat models lie in shambles and things are getting really messy. That's good science.