Another human non-specialty: menopause – 10/30/2023 – Suzana Herculano-Houzel

I have to control myself not to roll my eyes when they come to me with the old chant about humans being special. Enlarged brains, abnormally long childhoods, expanded longevity to the point where we have menopause and dedicated grandmothers in our species, who no longer reproduce, but only care for their offspring’s offspring. And this is all supposedly due to an “evolutionary advantage” of our lucky ancestors compared to their opponents. If all this is so advantageous, why does it only happen in humans?

It’s not advantageous – and it doesn’t just happen in humans.

Accepting premises rather than questioning them is always the easiest path, and they self-propagate. Let my colleagues say so, whose research depends on the validity of the premise of human exclusivity, which I have already demonstrated to be incorrect.

The supposed extension of human life also comes from another incorrect premise: that everything in life slows down as the body increases in size, which generally comes with slower metabolism. Growth also slows down, childhood lasts longer, the end comes later. In that case, we would expect humans to be shorter-lived than gorillas, about twice as large as us.

But no: we humans currently live 20 to 40 years longer than gorillas – who, in fact, usually die at reproductive age. In other words: gorillas can be mothers until the end; older humans can only become grandmothers, but no longer mothers.

This supposedly mysterious period of non-reproductive life, in “menopause”, is a so-called “evolutionary mystery”: a phenomenon with no known function – because almost 10 out of 10 biologists accept the premise that everything that exists must have evolved “to” have a function, or it would not constitute an evolutionary “advantage.”

Anthropologists then scrambled to find a role for menopause. And they actually arranged: “taking care of grandchildren”, when the uterus itself is no longer responsible for its own offspring.

The story went well until a team of anthropologists from several universities in the USA decided to study a large population of chimpanzees in a reserve in Uganda for more than 20 years. The results have just been published in the journal Science.

In that population, females around 50 years old no longer reproduce, like chimpanzees in other locations. But surprise: whether due to a lack of leopards (courtesy of hunting by humans), an abundance of fruit, or some other misfortune of luck, females in the Ngogo community of chimpanzees live to be 65 years old.

In other words: they have menopause.

But they don’t help their daughters, because females leave the community when they become adults. Nor do they take care of their children’s offspring, still in the community. No: menopausal chimpanzees live… because they can, I would say.

Chimpanzees are the species with the third highest number of neurons in the cerebral cortex, which actually predicts longevity impressively well. As a result, those species that are longest-lived, with many cortical neurons – such as whales, chimpanzees and us humans – are those that have the privilege of going through menopause. That simple.

And what is menopause for? For whatever we want and can do, well. We have no shortage of brain cells to find interests – including taking care of our grandchildren.

LINK PRESENT: Did you like this text? Subscribers can access five free accesses from any link per day. Just click the blue F below.