DAVID: How many other branches are yet to be found. There appears to be a large bush of hominins, when nothing else advanced. Looks like a purposeful push toward H. sapiens.

dhw: Looks like a large bush to me. Most purposes run in a straight line, don’t they?

DAVID: But all of evolution is a giant bush. That's the purposeful approach.

In that case, the purpose is a giant bush – not one single species.