These chimp handshakes, which are seen only among some of the primates, seem to differ from group to group in ways that aren't dependent on genetics or environment. That leaves cultural differences between groups as a possible explanation for why and how the hand-holding occurs.
"We think that this at least indicates that chimpanzees do not only respond to their environment instinctively or based on genetic predisposition," said study researcher Edwin van Leeuwen, a doctoral student at the Max Planck Institute for Psycholinguistics in the Netherlands. Nor do they learn in a vacuum, van Leeuwen told LiveScience.


