It's a truism of physical anthropolgy that behaviour doesn't fossilise. Time's eraser has wiped out what little data would remain from that time. However if we step ahead to c. 2.5 mya hominids and sharp stones seem to have formed a very useful association - some one began augmenting teeth with stone. Why? Perhaps earlier efforts at bashing stones and nuts produced crude blades that proved useful? We know chimps - some chimps - bash stones in the wild, so perhaps our LCA did the same.

Once we started making stone tools our ancestors began wandering far and wide, and as the recent finds from Georgia indicate that happened before our brains lept to Homo erectus level. Some sort of synergy between acquiring protein and bigger brains was surely involved and as neurological studies have shown an increase in one part of the brain of primates will cause the rest to follow. The ability to acquire and process food improved with each new innovation, making a bigger brain easier to sustain. But essentially modern size was attained c. 500,000 years ago, yet modern humanness waited until c. 120,000 years ago to spring forth. Why so?

Mystery is what drives Science forward.

Adam