"we find a long line of things that sort of lead up to humans in Africa"

Let me correct this. I think I know what I mean to say, but it's easy to get the wrong impression. The things we see that "lead up to humans" don't necessarily constitute a direct line. It's more like we can see things that are on branches that may be in the direct line, but are more probably on close side branches.

It's easy to think about evolution as a linear thing - the line from A to B - but that's only how it looks after the fact when we consider only A and B. I think it's a rare case when we can even tell whether A was a direct antecedent.


k