Grandparents have been going to bat for their grandkids for hundreds of thousands of years, a new study of South American foragers suggests.

Grandparents have been going to bat for their grandkids for hundreds of thousands of years, a new study of South American foragers suggests.

Paul Hooper, a biological anthropologist at Emory University, spent a decade studying the Tsimane people of the Amazon rainforest, who hunt, gather, and grow nearly everything they eat, as all humans did until large-scale agriculture was invented about 10,000 years ago.

Tsimane children depend heavily on both their parents and their grandparents for food, Hooper found.

And since the Tsimane live much like early humans did, this probably means grandparents have mattered for eons.

Three generations of a Tsimane family in 2009. Photo by Paul Hooper.

“Their efforts have likely been underwriting human society for hundreds of thousands of years,” Hooper says.

According to a paper that he and some colleagues recently published in Proceedings B, a scientific journal, Tsimane boys receive a significant amount of food from grandparents until about age 15, while girls depend on grandparents for food until about age 19.

Hooper’s results support the “grandmother hypothesis,” which postulates that early human grandmothers were often critical to the survival their grandchildren.

But Hooper found that Tsimane grandfathers are important, too.

Paul Hooper in 2014. His own grandmother, a zoologist, helped ignite his interest in science. Photo by the Santa Fe Institute.

The average Tsimane grandmother contributes 117 calories a day to her grandchildren, according to Hooper; the average grandfather contributes 223 calories a day to his.

Grandparents both hunt and garden on behalf of their grandkids: they supply them with meat such as deer, peccary, and armadillo and plants such as manioc, corn, and plantains.

Tsimane grandparents also play a key role in their grandkids’ educations, Hooper discovered. There isn’t much formal schooling among the Tsimane, but elders, who often live with their grown kids and grandkids, pass on their knowledge about making a living and other subjects through a vast repertoire of songs and stories.

When Tsimane grandparents aren’t teaching or provisioning their grandkids, they’re often having fun with them. The relationships between Tsimane grandparents and grandchildren tend to be loving, informal, and playful, Hooper says.