Why do we have periods?

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Nachos
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Why do we have periods?

Post by Nachos » Fri Oct 2, 17:59 2015

This is the most amazing thing I've read all year.

https://www.quora.com/What-is-the-evolu ... Iu&share=1

It makes so much sense. And it is written in an easy to read style for non-biologists.

My second favourite question is why do men have nipples. The answer: females have nipples and we all start developing the same in the womb. Boom!
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Re: Why do we have periods?

Post by antfancier » Sat Oct 3, 17:53 2015

Thanks for sharing. I found that really interesting, especially the fact that if we just keep having kids like we biologically are able to, then we'd have far fewer periods over our lifetime. For some reason that never occurred to me before. Also, I feel better knowing that it's ok for me to think of the baby growing inside me right now as a little parasitic because it actually is.

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Re: Why do we have periods?

Post by Meperidine » Sat Oct 3, 18:12 2015

As my college bio professor put it, periods used to be way less common because "for much of our evolutionary history, reproductive-aged women spent most of their time pregnant or lactating or dead." What with the way shorter lifespans humans used to have, theories about why we have menopause are interesting too!

Also, wow, fetuses sound like a-holes.
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Re: Why do we have periods?

Post by Gnarlbanya » Sat Oct 3, 20:30 2015

This was really interesting. I had no idea how unusual this was in the animal kingdom, either. Makes a lot of sense.

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Re: Why do we have periods?

Post by ablotial » Wed Oct 7, 13:59 2015

I agree, really interesting. When I was a teen and lived with my uncle for a year, their (unspayed) female dog bled a few times and I always thought she was menstruating, though the first time I saw it surprised me. Now I want to learn more about what goes on there.

I am also curious about this quote:
Normal mammalian pregnancy is a well-ordered affair because the mother is a despot. Her offspring live or die at her will; she controls their nutrient supply, and she can expel or reabsorb them any time.
Is this a conscious decision on the part of the mother? Or something that just happens? They way it is written here it sounds conscious, but maybe it is like when they said
The mother 'wants' to dedicate approximately equal resources to all her surviving children, including possible future children, and none to those who will die.
... although they used quotes there to show that it is not conscious.

Anyway, if the mothers of other species can tell that the baby is abnormal (or that they just don't feel like being pregnant right now) and get rid of it that easily, that's pretty interesting. It would really make the abortion discussion interesting (or moot?) if humans worked that way.

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Re: Why do we have periods?

Post by antfancier » Wed Oct 7, 16:50 2015

I found this article which sort of covers the same ideas but with more comparison to other mammals:
http://www.bbc.com/earth/story/20150420 ... ve-periods

The way it puts it, human embryos are so aggressive that we developed a very thick endometrium to protect ourselves so that when we don't get pregnant we have a lot of blood to shed, whereas other mammals don't have this issue and can just absorb the blood back into their bodies.

Slightly related is this article, which explains that babies are born when they are (not only because their head would get too big to fit through the pelvis) because the metabolic demands of growing a baby any longer than nine months would just be too much for a mother's body cope with.
http://www.americanscientist.org/issues ... nful/99999

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Re: Why do we have periods?

Post by Zeph » Wed Oct 7, 18:29 2015

Suffering through monthly periods is a disadvantage and women need healthcare to balance things out a bit. I've been uninsured most of my life and being handicapped by severe pain and heavy bleeding (med-light is manageable) for those first couple of days has caused me to miss work, take excess restroom breaks during inopportune times at my job, and miss social engagements.

Big-headed, bossy babies--why can't I just squirt out an armload of kittens?

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Re: Why do we have periods?

Post by Nachos » Wed Oct 14, 10:25 2015

ablotial wrote:Anyway, if the mothers of other species can tell that the baby is abnormal (or that they just don't feel like being pregnant right now) and get rid of it that easily, that's pretty interesting. It would really make the abortion discussion interesting (or moot?) if humans worked that way.
I know that rabbits can reabsorb their litter if their living conditions are unfavourable (I DID learn something from Watership Down!). Other than that I am now going to read that article, thanks antfancier!

Edit: That second article is bloody amazing. I love it :)
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Re: Why do we have periods?

Post by Sassquatch » Thu Oct 15, 20:47 2015

Nachos wrote:
ablotial wrote:Anyway, if the mothers of other species can tell that the baby is abnormal (or that they just don't feel like being pregnant right now) and get rid of it that easily, that's pretty interesting. It would really make the abortion discussion interesting (or moot?) if humans worked that way.
I know that rabbits can reabsorb their litter if their living conditions are unfavourable (I DID learn something from Watership Down!). Other than that I am now going to read that article, thanks antfancier!

Edit: That second article is bloody amazing. I love it :)
I don't think any animal makes the conscious decision to do this, but nature generally seems to limit reproduction when food is scarce. Animals have smaller litters or no children in bad years. Starving human women stop ovulating.

Reabsorbing the fetus or fetuses sounds really useful though, because then you don't all the nutrients you already put in!

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Re: Why do we have periods?

Post by Charli! » Sat Oct 17, 5:08 2015

Huh, I can't believe I never thought to question this before. Why did I never think to question this before??!? That's amazing,

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Re: Why do we have periods?

Post by Nachos » Sun Oct 18, 18:38 2015

Sassquatch wrote:
Nachos wrote:
ablotial wrote:Anyway, if the mothers of other species can tell that the baby is abnormal (or that they just don't feel like being pregnant right now) and get rid of it that easily, that's pretty interesting. It would really make the abortion discussion interesting (or moot?) if humans worked that way.
I know that rabbits can reabsorb their litter if their living conditions are unfavourable (I DID learn something from Watership Down!). Other than that I am now going to read that article, thanks antfancier!

Edit: That second article is bloody amazing. I love it :)
I don't think any animal makes the conscious decision to do this, but nature generally seems to limit reproduction when food is scarce. Animals have smaller litters or no children in bad years. Starving human women stop ovulating.

Reabsorbing the fetus or fetuses sounds really useful though, because then you don't all the nutrients you already put in!
Exactly! It's probably as conscious a decision as digestion. So the body knows more of what it's doing than the mind has an input in.
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