@Enzyme
Further to your point about defining intelligence, it also depends on where the origin on the x axis is. If you take the amoeba as the baseline, then the range of human intelligence is going to appear as a sharp spike at the top end. But if you base it on, say, chimpanzees, it would be a much broader curve.

I suppose the most important factor for our evolution is how intelligent you need to be to survive as a human. Which nowadays is almost irrelevant, given the health care available.

It would be interesting (but effectively impossible) to be able to quantify intelligence to see if and how the human race as we know it has changed over the last few tens of thousands of years.
( K2k6 has a proper job these days, Wed 23 Apr 2008, 13:06, Reply)