When did the human brain start to expand?

[IgnorantApe]

I'm finding a hard time finding information on this. Can anyone clarify? As I understand it, the brain started to expand when humans first started using tools--but when was that, 2.5 million years ago?

I also heard there was a sudden spike in increased brain size around 200,000 years ago.

Any clarification much appreciated.

[CarlosG]

Some interesting research has been done on a few genes that have been implicated in the rapid volume expansion of the human brain, namely ASPM and microcephalin. Mutations in these genes now leads to a condition called microcepahly, where the valume of the brain shrinks by approx. 70%. This size, it has been said, is very similar to a common ancestor of humans and great apes, leading them to believe that initial mutations were favored and the brain grew as a result.

If you have some time this link gives an overview of the research:
http://www.rationalskepticism.org/evolu ... t1784.html

[IgnorantApe]

Thanks. I think I know some people with undiagnosed microcepahly.