Despite some physical similarities to our great ape cousins, humans are distinguished by big brains. Brain volume in humans is roughly three times greater than it is in apes. Humans are also distinguished by their ability to create culture—tools, languages, art, institutions, societies, and governments—culture that accumulates modifications over time. Humans transmit their cultural knowledge to subsequent generations, who adopt it and use it as a foundation for cultural innovations that they then pass on. Although nonhuman animal cultures (or proto-cultures) exist, such as seen in chimpanzee termite fishing in the Gombe Stream area, their cultural practices are usually limited by geography and do not progress over the generations. There is no evidence of the “ratchet” effect in nonhuman animal cultures as opposed to human cultures—the accumulation, transmission, and progress of cultural traditions over time. And there are reasons to assert that the differences in generativity between nonhuman and human cultures rest on species differences in teacher and learner transactions.