"You should not call a bully an alpha male," de Waal said. "Someone who is big and strong and intimidates and insults everyone is not necessarily an alpha male." He says many chimpanzees know being kind and loving is a way to win over fans, whether by tickling babies, sharing food, or engaging in a kind of primate political campaign. "You don't need to be the biggest and strongest male," de Waal said. "The smallest male, if he has the right friends and keeps them happy, or he has female support, he can be the alpha male."

There is the usual buzz of commuters rushing to make their evening trains, but even the seasoned travelers here are looking up.