Despite being separated by 95 million years of evolution and utterly different environments, female chimpanzees and dolphins have a whole lot in common.

They’re the bedrock of family life, hardworking moms who feed and raise kids while their fathers are out roaming.

“If we want to understand what is driving social systems where males do not provide care,” says Heidi Pearson, a behavioral ecologist at Stony Brook University, “we should be looking at females.”

In a study published June 22 in Evolutionary Anthropology Pearson compares the behavior of female chimpanzees and bottlenose dolphins in...