Pop science specialist Alison Gopnik, author of several books, including The Philosophical Baby (2010) and Scientist in the Crib (1999) explains grandmothers:

On an evolutionary timescale, Homo sapiens emerged only quite recently. Yet in that short time, we have evolved a particularly weird life history, with a much longer childhood and old age than other animals. In particular, were very different from our closest primate relatives. By at least age seven, chimpanzees provide as much food as they consume, and they rarely live past 50 theres no chimp equivalent of human menopause. Even in forager cultures, where growing up is accelerated, children arent self-sufficient until theyre at least 15. Whats more, even in communities without access to modern medicine, if you make it past childhood you might well live into your 70s. We live some 20 years longer than chimpanzees and, except for a few whale species, particularly orcas, we are the only mammals who systematically outlive our fertility

Chimpanzee mothers do almost all the childrearing. But humans evolved exceptionally extended and varied sources of caregiving to deal with their costly babies, including fathers who take care of the kids, post-menopausal grandmothers, and alloparents other people who help to raise children. Prairie-vole dads, orca-whale grandmothers and rhesus-monkey alloparents also help to raise babies, but these kinds of care are rare among mammals. No other species except humans appears to have all three kinds of care.

If it were not rigorously pounded out of you by a pop science education, youd almost think that human intelligence has something to with longevity

Human grandmothers are treasured, not eaten.

Here are some instances of pop science, over the years, trying to understand grandmotherhood:

2010 Despite its anecdotal support and intuitive appeal, the grandmother hypothesis lacked much quantitative proof showing that it was possible for longevity to evolve from grandmothering, says Kachel, whose team ran a mathematical simulation to test the theorys plausibility.

2011: The hazard of death for Dogon children was twofold higher if the resident paternal grandmother was alive rather than dead. This finding may reflect the frailty of elderly grandmothers who become net consumers rather than net producers in this resource-poor society. Mothers were of overwhelming importance for child survival and could not be substituted by any category of kin or nonkin. The idea of cooperative breeding taken from animal studies is a poor fit to the complexity and diversity of kin interactions in humans.

2016: Menopause is an evolutionary puzzle, as an early end to reproduction seems contrary to the laws of natural selection, where passing on genes to the next generation is the main purpose of life. Yet female humans, and some other mammals, spend up to a third of their lives unable to reproduce.

2017: Study fails to discover why old women exist: Evolution has no further use for us once we lose the capacity to reproduce. Theory tells us, in fact, that we should expect to shuffle off quite promptly once were out of the parenting game. So, how then do we understand the fact that women live for many decades beyond menopause?

2019: Women living past menopause helps grandkids survive, but that benefit doesnt always withstand the test of age and distance, two studies suggest.

Wow. Theyre getting closer all the time, arent they?

Alternatively, wisdom matters. And wisdom is not a material thing. Its a human thing.

Anyway, hug or otherwise contact your grandma while you can.

Link:
Some Scientists Struggle With Why There Are Grandmothers - Walter Bradley Center for Natural and Artificial Intelligence