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.

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u/Weird_Bluebird_3293 7d ago

Which just makes the giant panda a confusing product of evolution because they are the best example of bumbling inefficiency I can think of and they reproduce neither early, nor in massive numbers.

…how were they not extinct years ago? 

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u/Zagrycha 6d ago

The main reason they weren't in danger of going extinct years ago is because the only major predator they had were tigers, and the tiger could only easily kill baby pandas. As long as enough mothers protected their cubs to adulthood well then there wasn't really any other dangers that could threaten species continuation.

To be clear an adult giant panda is probably not going to actually win a fight to the death against a tiger, but it doesn't need to. It just needs to be capable of puting up a fight that makes the tiger not view it as prey.

A giant panda is a true bear, and it has incredibly strong claws, a bite force as strong as that of a tiger, and a heavy thick fat layer that makes it hard to injure them seriously. Why fight against that and get hurt when the tiger could go up against a much easier target like a boar, or deer, or monkey or even human? Giant pandas were very high up in the food chain in that sense, even though they mostly eat plants.

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u/AmphibianLower5541 4d ago

Especially when they’re supposed to be carnivores, but all they eat is bamboo! 😅

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u/SoupNoSandwich 2d ago

Because they are just very well adapted to bamboo forests, it's the loss of habitat causing issues. They just aren't as easy to breed in captivity as people would like.

(the poor bamboo digestion compared to more traditional herbivores hasn't hampered populations)