Why menstrual cycle but not something else?

Question

I know that it's superior from laying eggs like birds, reptiles and amphibians, and I basically how it works. I just don't know why evolution "selected" (sorry, I'm not native so I don't know the correct terms) menstrual cycle, it's a disadvantage in ways:
_Make the females tired and less active
_During the cycle, the females are easier to be inflamed by infections.
_Wouldn't the smell of blood attracts and guides the predators to her place?

So, what confusing me is that why, in billions yrs of evolution that have given lifeforms an incredible complexity and fitness, the disadvantaged menstrual cycle didn't outcasted? Why it but not sth better?

I'm still in highschool, in a developing country and the sex education isn't throughout, so I hope you guys can answer me: why menstrual cycle?

Thanks in advance! :D

manigfeald · Accepted Answer

Well, I guess the root lies in energy expenditure. Some anthropologists have questioned the energy cost of rebuilding the endometrium every fertility cycle, and it appears that the energy savings of not having to continuously maintain the uterine lining more than offsets energy cost of having to rebuild the lining in the next fertility cycle, even in species such as humans where much of the lining is lost through bleeding rather than reabsorbed. Even in humans, much of it is re-absorbed. So yeah, the benefit is less energy expenditure.

It'll take really long to state most of the other points, so I'd suggest, you take a look at Strausmann's Study. I've attached the link below. It provides quite a detailed explanation in response to your question.

By the way, in response to your 3rd point on attracting predators, most mammals reabsorb their linings (humans are one of the few exceptions). So there's less chance of them being detected in the wild.

=42 · Answer

Survival of the fittest (evolution) would mean that an inbuilt handicap (menstruation) guarantees that the strongest have a better chance to survive than the weak. Evolution isn't about everyone surviving, it's about favouring the strongest, to guarantee the survival of the species.

Dude · Answer

Humans are almost unique in their reproduction. So it's hard to compare to other animals.

As for things like the blood attracting predators, that was likely not an issue, we were already near the top of the food chain long ago.

Are u sure that menstruating makes u more prone to infections?  I've never heard that

Anonymous · Answer

Menstruation was uncommon.  Women spent most of their adult lives pregnant.  Pregnancy is WAY more disadvantageous than menstruation, and yet it happens.  Fortunately we're a social species, and women who are pregnant get some protection from the group.
Edit:  Ask your grandmother about this.  Big families were the rule before contraception.

Anonymous · Answer

just shows that its really a part of the curse God put on us for Adam and Eve eating from the tree of the knowledge of good and evil. another point for creationism bring on the flood of thumbs down.

Want more answers to why Evolution makes no sense when closely examined? go to Answers in genesis.org

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Why menstrual cycle but not something else?

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