More on Menopause

[Tuckerfan]

In this column Cecil discusses the so-called “granny theory” as to why women undergo menopause and mentions that there’s a few holes in the theory. A new theory says it’s to reduce competition among women.

In this paper, published in the journal PNAS, the researchers propose that the timing of reproductive cessation in humans is best understood as an evolutionary adaptation to reduce reproductive competition between generations of females in the same family unit.

Reproductive competition is ubiquitous in other cooperative vertebrates, but up to now its potential role in human life history evolution has been overlooked. The research demonstrates that humans are unique among primates because there is almost no overlap of reproductive generations. In natural fertility populations, women on average have their first baby at 19 years and their last baby at 38 years; in other words, women stop breeding when the next generation starts to breed.

[SiXSwordS]

I’m still reading the article in your link, but I have to wonder if this isn’t coincidence.

from Cecil’s column
Female mammals remain fertile long enough to be able to raise their young before they die, and no longer.

If menopause were an adaptation, wouldn’t menopause start much earlier, so that women whose life expectancy was ~50 would benefit or offer some benefit to their offspring. The coincidence would seem to be that, now that life expectancy has been artificially drawn out, women live long enough to see their grandchildren reach puberty rather than just their youngest offspring.

[SiXSwordS]

from the linked article

Women everywhere experience a rapid decline in fertility after the age of forty, culminating in menopause around ten years later. Our study helps to explain why this phase of rapid ‘senescence’ of the reproductive system starts when it does, and why women, on average, stop having children a full ten years before the onset of menopause.

Emphasis Mine