Menopause

[Itoero]

How do you think menopause evolved? What evolutionary succes did it give?

There are many theories, but no proven of course.

They found it in many other animal species.

"Menopause has been observed in several species of nonhuman primates,including rhesus monkeys andchimpanzees.Menopause also has been reported in a variety of other vertebrate species including elephants, short-finned pilot whales, iller whales, narwhals, beluga whales, the guppy, the platyfish the budgerigar the laboratory rat and mouse, and the opossum However, with the exception of the short-finned pilot whale, killer whale, narwhals, and beluga whales, such examples tend to be from captive individuals, and thus they are not necessarily representative of what happens in natural populations in the wild. "https://en.wikipedia.org/wiki/Menopause

[Sensei]

"Ovarian aging

As women age, they experience a decline in reproductive performance leading to menopause. This decline is tied to a decline in the number of ovarian follicles. Although about 1 million oocytes are present at birth in the human ovary, only about 500 (about 0.05%) of these ovulate, and the rest are wasted. The decline in ovarian reserve appears to occur at a constantly increasing rate with age,[17] and leads to nearly complete exhaustion of the reserve by about age 52. As ovarian reserve and fertility decline with age, there is also a parallel increase in pregnancy failure and meiotic errors resulting in chromosomally abnormal conceptions.[medical citation needed]"

https://en.wikipedia.org/wiki/Ovary

 

Edited December 15, 2018 by Sensei

[John Cuthber]

1 hour ago, Sensei said:

"Ovarian aging

As women age, they experience a decline in reproductive performance leading to menopause. This decline is tied to a decline in the number of ovarian follicles. Although about 1 million oocytes are present at birth in the human ovary, only about 500 (about 0.05%) of these ovulate, and the rest are wasted. The decline in ovarian reserve appears to occur at a constantly increasing rate with age,[17] and leads to nearly complete exhaustion of the reserve by about age 52. As ovarian reserve and fertility decline with age, there is also a parallel increase in pregnancy failure and meiotic errors resulting in chromosomally abnormal conceptions.[medical citation needed]"

https://en.wikipedia.org/wiki/Ovary

 

Yes, we know.
The question is "why hasn't evolution 'fixed' that?"

[Sensei]

3 minutes ago, John Cuthber said:

The question is "why hasn't evolution 'fixed' that?"

You know that evolution is not working this way.

Majority of wild female mammals are dead long before oocytes are exhausted.

Edited December 15, 2018 by Sensei

[John Cuthber]

22 minutes ago, Sensei said:

Majority of wild female mammals are dead long before oocytes are exhausted.

The majority of female humans are too- because they die in childhood (except in the affluent bits of the world which are rare and new so they aren't a factor in evolution).

However, unlike most animals, female humans who live long enough to bear children, typically do reach a menopause.

That's unusual and cries out for an explanation.
One hypothesis I have heard is that our species is so heavily dependent on knowledge and communication that having grandmas around to help is a significant evolutionary advantage.

[Itoero]

57 minutes ago, Sensei said:

You know that evolution is not working this way.

Majority of wild female mammals are dead long before oocytes are exhausted.

But then why didn't they find it in a lot more animals then the ones mentioned in Wikipedia? If it's only due to aging then they should find it in many animals, past a certain age.

They also found it in birds and fish.

And menopause typically only happens in social species wher female members of the group assist in child rearing.

Edited December 15, 2018 by Itoero

[swansont]

AFAIK it falls under the umbrella of senescence and the basic argument is that can be advantageous to have additional defenses available to you earlier in life, because there are so many ways to die young. It makes no sense to be fertile at 80 if that comes at a cost of being less fertile while younger (and there are always going to be trade-offs) and being killed before you reproduce.

But one must note that there is more than one reproductive "strategy" in play, because there are so many variables involved, and you can't simultaneously optimize all of them.

[Itoero]

The occurrence of menopause evolved. The relative time at which female animals can live after their reproductive years has past differs.

Two years ago, scientists suggested whales do this to focus their attention on the survival of their families rather than on birthing more offspring. But now this same team reports there’s another—and darker—reason: Older females enter menopause because their eldest daughters begin having calves, leading to fights over resources. The findings might also apply to humans, the scientists say.https://www.theguardian.com/science/2017/jan/15/killer-whales-explain-meaning-of-the-menopause

Also, family groups (of killer whales)are often based on matrilines consisting of the eldest female.(matriarch).https://en.wikipedia.org/wiki/Killer_whale

"As chicken farmers know, a hen’s egg production slows substantially around age four. But that’s not a sign that she’s running out of eggs. Older hens are simply more sensitive to changes in diet or light, and they stop laying when living conditions worsen. "https://slate.com/news-and-politics/2011/03/do-birds-go-through-menopause.html

The reason they often say certain animal species have menopause is to make a distinction between animals that have a rather long life-span after the end of the reproductive years and animals that have a short or no life span after the end of the reproductive years.

It's related to whether animals live in captivity or not.