Why is the human brain so large?
We have no idea exactly why humans have gotten the large brains they have today. It is clearly something in the human lineage that has predisposed humans to larger brain size, but we don’t even know what the exact pattern was. All we can say is that 2 million years ago, average brain sizes among hominids were not much bigger than they are among apes today. 2 million years down the line, we have a brain that is 3 times that size. We don’t know what happened in-between. We don’t know enough about the number of species that have existed among hominids over the last 2 million years. We don’t know enough about the time range of those species or the range in brain sizes. All we have is this simple observation that 2 million years ago our precursors had small brains and today we have large brains. We don’t know what happened in the middle and we can’t make the assumption that it was a linear transformation, linear gain in brain size. In fact, it almost certainly wasn’t. How important was fire
