But behavior does not fossilize. Louis reasoned that any behavior common to chimpanzees and humans today might well have been present in the apelike humanlike common ancestor which we shared, he believed, several million years ago. And if this was so, then those same behaviors were probably present also in the earliest true humans. This line of reasoning, new at that time, is widely accepted today, particularly as the geneticists tell us that our genetic material, our DNA, differs from that of chimpanzees by only a little over 1 percent.
