I should make myself more clear. I did not mean to say (and I did not say at all) that the evolution of human language parallels human evolution. The evolution of human language sheds light on the movement of human populations throughout the last few thousand years, but the time scales are too vastly different for the evolution of languages to reflect human evolution.
I mean to say that the rules that seem to govern the evolution of language are largely parallel to the rules that govern the organic evolution of all living things (again, on a different scale of time for most organisms.) For a simple example, consider a human population in the past that - for whatever reason - becomes divided into two populations that are more-or-less isolated from one another. If the isolation persists over centuries, two distinct languages will likely result (and neither will remain exactly the same as their original language.)
