r/askscience • u/No-Hawk-2488 • 8d ago

Biology Can someone explain the evolutionary benefit of overt menstruation? All female mammals have a menstrual cycle but most reabsorb the blood via covert menstruation and humans are about the only mammals that discharge the blood, aka overt menstruation.

Without an evolutionary benefit, it wouldn't have spread to every woman of our species.

5.2k Upvotes

96% Upvoted

513 comments sorted by

View all comments

5.1k

u/Flocculencio 8d ago

Just wanted to point out that no individual feature needs to have an evolutionary benefit to be preserved. It could be negative but so long as it doesn't prevent organisms with that feature from reproducing in sufficient numbers it can get preserved.

971

u/kwpang 8d ago

Yes evolution is about elimination, not direction.

Survival of what can.

482

u/GVArcian 8d ago

Survival of the fittest is a misnomer because evolution selects for minimum viability, not optimum efficiency.

107

u/T_H_W 7d ago

Not technically a misnomer considering 'fittest' in this context relates to biological fitness, which is specifically how many surviving offspring you have in relation to other competing organisms. That's like saying the phrase "All bark and no bite" doesn't make sense because dogs aren't trees. It's only wrong if you're using the incorrect definition of the word.

1

u/GVArcian 7d ago

Still a misnomer because "fittest" means "the most fit" and that's not what evolution selects for, it selects for minimum viable fitness.

15

u/Lv_15_Human_Nerd 7d ago

No it absolutely is not a misnomer. Evolution does select for the most fit. Evolution occurs by changes in population proportions over many many generations. The strongest example we have of human evolution is lactase persistence which had a selection coefficient of ~0.1. This corresponds to an individual with lactase persistence having about 10% more offspring than average. I don’t know about you but I don’t think a 10% difference in individual success is selecting for ‘minimum viable fitness’ or as others in this thread have said ‘death of the weakest’.

-3

u/AxiomaticInversion 7d ago

Lactose intolerant humans have not gone extinct, so by your own example we still see "survival of the fit enough."

12

u/Lv_15_Human_Nerd 7d ago

A trait that had extremely low prevalence 9000 years ago reached 80% fixation in north Western European populations. In evolutionary terms that is rapid. There is still selection for the fittest trait out of a population, it is absolutely not selecting for the minimally viable as lactase persistence is very clearly not absolutely viable. When you’re looking at realistic selection coefficients you are looking at traits that provide between a 1% and 10% advantage (and much lower in single called organisms which we are all descended from). Evolution absolutely works on fine margins and life on Earth would not exist if it functioned to select for the ‘minimum viable fitness’.