Chimpanzees are our closest living genomic relatives, but they lack the bipedal locomotion,
markedly enlarged brains, and advanced communication skills of humans. This has led
many to view them as “primitive” and to presume that their behavior and anatomy are also
primitive. If true, they could serve as models of our last common ancestor (LCA), ie, a
territorially aggressive knuckle walker, reliant on vertical climbing and below-branch
suspension to access the high canopy as a ripe-fruit frugivore. Ardipithecus now provides …