So why do male chimps share their meat? Because others harass them:
Much is hereby explained about the behavior of human children, who seem to have internalized this rule that the more you harass, the more you get.
A more likely explanation is that chimps share meat because others beg, [primatologist Ian] Gilby says. He has found that the more a chimp eating meat is harassed, the more he shares; that begging slows the speed at which chimps eat meat; and that begging tends to stop once meat is shared.
"It doesn't involve males thinking about who owes them favours," Gilby says. "It is essentially 'you're in my face bugging me, because you're there harassing me for meat I can't eat'."