The saying “It takes a village to raise a child” can be seen in every community around the globe. In addition to parental guidance, children are also shaped by extended family members, teachers, coaches, neighbors, and friends. But why does anyone care about the well-being of a child that isn’t theirs and participate in allomaternal care, also known as cooperative breeding? Wouldn’t it be more advantageous for all parents to only devote their energy and resources on their own offspring?
In order to answer those questions, researchers needed to examine the origins of altruism, which is the practice of performing acts for others without expectation of reward. Researchers examined groups of primates to learn more about how concepts like altruism and cooperation evolved and the different forms it has taken on. The study was led by Judith Burkart from the University of Zurich and the paper was published in Nature Communications.
Humans and chimps split from a common ancestor about 5-7 million years ago, whereas apes and monkeys diverged roughly 24 million years ago. Chimps are not nearly as eager to cooperate as humans, though some monkey species are. The researchers designed a test in which a food treat was placed on a sliding board. The individual moving the board can bring the treat within reach of others within the group, but will not be able to get the food themselves.
The experiment was carried out in 24 groups across 15 species of primates, including 3 groups of human children who were 5-7 years old. The food selection was tailored for each group, in order to test whether or not the primate would willingly give up a desired treat. The researchers found that species who most often utilized the “it takes a village” style of cooperative breeding were also more likely to help someone else get a treat, even though they didn’t get one themselves.
“Humans and callitrichid monkeys acted highly altruistically and almost always produced the treats for the other group members. Chimpanzees, one of our closest relatives, however, only did so sporadically,” Burkart explained in a press release.
The researchers also examined possible relationships between giving a treat to a friend and other cooperative behaviors, such as group hunting and complex social bonds, as well as relative brain size. Cooperative breeding was the only trait that showed a strong linear correlation and was the best metric for predicting altruistic behavior.
“Spontaneous, altruistic behavior is exclusively found among species where the young are not only cared for by the mother, but also other group members such as siblings, fathers, grandmothers, aunts and uncles,” Burkart continued.
However, cooperative breeding is likely one of many factors that could have influenced the evolution of altruism among humans. Over the evolutionary history of our ancestors, living in cooperative groups may have benefitted greatly from high cognitive abilities, especially regarding things like language skills.
Burkart concluded: “When our hominin ancestors began to raise their offspring cooperatively, they laid the foundation for both our altruism and our exceptional cognition.”