Pan troglydites

Chimpanzees provide a useful benchmark for hominid evolutionary comparisons.

Over 98% of chimpanzee and human DNA is genetically identical. This is because hominids and chimps descended from the same ancestor species of large ape, perhaps Ardipithecus, around 7 million years ago -- just yesterday, in the evolutionary measure of time.

Hominid evolution is chiefly told in brains and bodies. Adult chimpanzees weigh around 30 kilos with a brain capacity of 300cc to 490cc. They are not bipedal but can stand and walk erect for short distances.

In captivity and in the wild, chimps display a remarkable range of cognitive and social abilities. They are the closest of any ape to human social structure, group behavior, intercultural variation, and diet; they use tools and have been experimentally trained to recognize simple symbol systems. In most respects, chimpanzees stand at the horizon of human nature: the animal least like us in appearance with behavioral attributes still recognizably like our own.

Yet chimpanzee and human skulls obviously differ -- in the slant of the face, the large front canine teeth, the dominant eye ridges, and the ratio in size between the face and the brain -- despite the fact that in evolutionary terms we are closely related. The moral: fossil differences may lead us to exaggerate the imputed behavioral and cognitive dissimilarities among hominid species.

Chimpanzees are a sociable, nurturing, playful, bickering, stately, cunning, practical, casual, curious, omnivorous, sexually preoccupied, trusting but sometimes fearful kind of animal. And so am I.