First of its kind
Unlike other primates, humans are “cooperative breeders”, which means that mothers get help raising their offspring. Rilling, who had previously conducted similar studies on fathers, wanted to turn his attention to grandmothers to explore an anthropological theory known as the “grandmother hypothesis”.
That hypothesis establishes that the evolutionary reason human women tend to live long lives – well beyond their own reproductive years– is to give well-being to your own adult offspring and your grandchildren. Evidence supporting this hypothesis has been found in societies that include the Hadza, a group of hunter-gatherers in northern Tanzania, in which grandmothers fed their grandchildren nutritious tubers. The effect has also been observed in other species such as elephants or killer whales, which like humans – but unlike the vast majority of mammals – also experience menopause. “This is really the first look at the grandmother’s brain,” Rilling said, explaining that studies with brain scans in older people usually focus on probing for conditions like Alzheimer’s.
The grandmothers, who lived in the Atlanta, Georgia area, and came from diverse economic and racial backgrounds, also filled out a series of questionnaires. And the grandmothers who reported a greater desire to be involved in providing care had greater activity in the brain regions of interest. Finally, when comparing this new study with the results of her previous work with parents, Rilling found that -in general- grandmothers activated regions related to emotional empathy and motivation more intensely. But he assured that this finding is only average and does not necessarily apply to all individuals.
Rilling also interviewed each of the participants to get an idea of the challenges and rewards of being a grandmother. “Consistently, the challenge that arose the most was the difference of opinions with the parents regarding the way to raise the grandchildren, their values, and the constant struggle to stay aside on these issues,” he said. On the contrary, and “with this we were joking, but many of them talked about how to give back to the grandchildren, because it is not a full-time job.”
Many grandmothers felt that they could be more present now that they are relieved of the pressure in terms of time and finances that they experienced when they were raising their own children. “So many of them actually said they were enjoying being grandmothers more than they enjoyed being mothers,” she said.