Expert: John Shea - 1/10/2007

Question
Hello, John.

Some years ago, I saw a documentary on the early apes.  The state of development I now have in mind discussed a particular divergence between species.  (I hope I describe this adequately):

From what I remember, one brance of the ape family, the "root eaters" (my phrase), owing to their need to forage ever deeper for ever-harder root stems, had developed over time, ever-larger jaws.  This survival strategy, however, eventually having reached its peak potential, that particular branch of ape died out, its position taken over by apes with higher brainpower (and smaller jaws) and which consequently had learned to forage for easier and wider available food sources.

What I can't recall is the names of these two particular sub-species. Can you help me out here?

regards,
Dan O'Hanlon

Answer
Dan
The "apes" you are describing are called "Australopithecines".  They lived in Eastern and Southern Africa between around 1.5-4.0 Million years ago.  Over this period they seem to have evolved from a common ancestor into two groups of species.  One group, the "robust" australopithecines (aka Paranthropines) developed massive teeth, jaws and other cranial adaptations to chewing tough, high-fiber materials (among which roots would number).  The other group, the "gracile" australopithecines retained less specialized chewing adaptations.  They are thought to have evolved into early species of the Genus Homo (H. habilis, H. ergaster, H. erectus) around 2 Million years ago.  It is the early Homo species, not the australopithecines who evolved significantly larger brains and more complex diets.
Cheers
John Shea