Frans de Waal, who used his study of the inner lives of animals to build a powerful case that apes think, feel, strategize, pass down culture and act on moral sentiments — and that humans are not quite as special as many like to think — died on Thursday at his home in Stone Mountain, Ga. He was 75.
The cause was stomach cancer, his wife, Catherine Marin, said.
A psychologist at Emory University in Atlanta and a research scientist at the school’s Yerkes National Primate Research Center, Professor de Waal objected to the common usage of the word “instinct.” He saw the behavior of all sentient creatures, from crows to persons, existing on the same broad continuum of evolutionary adaptation.