Menopause and life expectancy

Cecil's Columns/Staff Reports
21

Ok,

I just talked to a Nurse Practicioner on this because of the correction by Dtilque.

Yes, there are many many ova that are not fertilized. However, they don’t all wait up there to drop one at a time until menopause strikes.

Evidently, for every ovum that drops, there are hundreds or thousands that die off (every month)

So, my initial thought seems to be on track:

There comes a point where a premenopausal woman doesn’t have enough oocytes to support menstruation. And at that
point you have “The Change”

thanks again, dtilque for pointing me in the correct direction.

22

I don’t think the number of available oocytes dictates whether menstruation still occurs. It’s more complicated than that.

23

It seems to me the unanswered question is still why women go through menopause and men don’t. Why do women stop making eggs (or maturing them, or finish having them all die off, or whatever) and men keep making sperm even when the willie won’t?

24

The scientific answer to this is unknown. Maybe it’s just because we deserve a break?
(though it doesn’t feel like one yet for me… birth control pills were a hell of a lot easier)

25

IMHO, its because women have almost always been the primary caregivers of their children, so if the father dies, its not as much of a loss-as far as taking care of the child was concerned.
Nowadays things are different.

26

Perhaps because there are significant health risks to the mother and child if she becomes pregnant at the age of 50, 60, fill-in-the-blank. Whereas there are few risks to a man if he gets a woman pregnant and he is 50, 60, fill-in-the-blank. So there’s no selection against men who remain fertile into old age (and perhaps even some selection for).

27

easy e, I don’t think there have been any 60-year-old women who have gotten pregnant.

28

I guess that perhaps throughout history those women who had a tendency to get pregnant at age 60+ did not survive that pregnancy and so did not pass on their genes. As such, the “being able to get pregnant at 60” characteristic would disappear…?

Um… but this perhaps assumes that such women didn’t produce offspring earlier in their life, cos if they did it would mean the “being able to get pregnant at 60” characteristic would still be passed on…
– Quirm

29

Age of menopause is genetic to some degree. Women tend to reach menopause around the same time their mothers did. Re. the earlier theory, yeah, I would think the women who reached menopause latest would be the ones to pass on the most of their genes.

Pregnancy, especially in the early days, was a lot easier on younger women, so menopause makes sense in that regard, to allow women to survive longer.

At least I’m not balding.

30

First, let me start with: I’ve never thought much of evolution as a theory. It asks too much and explains too little. That said, there are a couple of problems with Cicel’s answer…

First, talking about evolution and the average of anything is senseless. By definition evolution works with the extreme ends of the bell shaped curve rather then the center. The first individual that develops any particular mutation will pretty much be unique. It doesn’t get more extreme then that. To pass it on, that uniqueness needs to be useful for survival. It’s not until generations later that the mutation would be in the middle of the bell shaped curve.

Second, the old woman theory mutations or adaptations that are counterintuitive in terms of the classical evolution theory. You might think of it as addressing social evolution rather then the other kind. The point being that this theory shows how a mutation that limits the number of offspring, which would be considered counter survival in classical evolution terms, could be a beneficial mutation.

The idea is that any particular social group is going to survive and grow if there is some sort of history. Since on the whole, women live longer then men, the theory discusses women.

The example of this theory that I remember is this… A social group encounters some cyclic problem where the cycle spans more then 2 generation. A bad drought for instance. The group survived the last time obviously (because they are still here). The best chances for survival is if there is some old woman around who remembers how they survived it the last time. Anytime you have an only an oral tradition (writing not having been invented), those things invented 2 or more generations ago to handle tough times need to be remembered and described at some later time. The group/family with the most old women has an advantage over the other kind.

Having old women that aren’t making babies and are possible infirm can’t be considered a classical survival benefit. Deficits in food consumption and slower travel come to mind. This theory says otherwise.

31

JillGat (and others): I dealt with related issues in a paper for a bioethics class a couple of years ago. The Seven Sexes of Mankind, http://www.romm.org/rhetoric/sevensexes.htm . Doesn’t answer why, but does try to develope a vocabulary for discussion, as in your use of the term “parimenopausal”, which I’ve never encountered before (but then, I haven’t looked).

32

Frankly I don’t see any mystery about menopause, either its timing or purpose. Humans are distinct from other primates and mammals in having an unusually long period of infant dependence. I’ve seen it argued that this is due to a combination of walking upright, resulting in a narrow birth canal, and having an unusually large mature brain, so that much brain development has to take place after birth. Note that human mothers most often bear litters of one. The strategy of human reproduction is to invest parental energy in raising a small number of offspring instead of in bearing large broods who are soon thrown on their devices to survive. Therefore it is a survival advantage to have a living mother at least to the end of adolescence. Consider the reaction many people have to fertility treatments that allow women over 50 to bear children.

33

For that matter, humans are also distinct from other mammals in living for an extraordinarily long time. Is this perhaps related?

34

I’m pretty darned amazed that someone doing research on menopause wouldn’t have run across the term “perimenopause.” It describes the several years preceding the end of menses, during which many women experience hot flashes, mood swings, etc. There are a number of books out with “Perimenopause” in their titles, even.
Here is another response to Cecil’s column, sent in to Cecil by a reader in Hawaii:

Dear Cecil,
I just finished reading your column in the Honolulu Weekly about menopause.
I found it interesting, but incomplete. Your sources are good, however, I
think that a quick review of a couple of articles from paleoanthropologists
Lovejoy and Milford Wolpoff might provide some information that would
suggest that menopause is the result of other evolutionary influences
totally unrelated to a biologists claim of just “growing old.” In other
words its all about genes, reproductive fitness, and gene flow. Unlike many
mammalian species, human females do not advertise sexual readiness in the
same way that, say, baboons or other primates do. For example, baboons,
chimps, and others have large bulbous red swellings advertising their sexual
readiness. It is postulated that this readiness and advertisement for mates
has been lost over our evolutionary history as we have evolved in the past
4.5 million years as humans came out of the trees and out of Africa, and
formed family and social bonds. However, sexual readiness, the ability to
hold mates, and the accompanying providing for offspring by those mates, is
now tied to who the father of the offspring are. Since only the mother can
ever really know who the father is, it was more advantageous for a woman in
early homo society to mate with as many men as possible in order to have as
many men provide for her as possible, regardless of whether she became
pregnant or not, as it behooved each male to provide for a possible
offspring who might be carrying his genes. It is also quite likely that
since the stress of living and the age of these early homos were shortened
that menopause may have occurred at an earlier age. But you can bet the
women weren’t talkin’! On the other hand since early homo societies were,
by definition, short lived, menopause may not have come into play. This is
treatise that Lovejoy explores. One can never know. Also the “granny
hypothesis” is not as farfetched–it is still being explored by
paleoanthropologists, paleogeneticists, and cultural anthropologists.
Evolutionary biologists just don’t have all the information.

Anyway, as we became homo sapiens sapiens menopause was still not an issue,
as menopause, even if women lived that long (and the archaeological record
has shown that members of homo Neandertalensis and earlier species predating
homo sapiens sapiens another debate that is alive and lively that we won’t
get into here did live to as old as 50) would never be evident to males, and
women would continue to copulate with as many men in an attempt to hold
their mates in order to have them provide food, shelter, and other
necessities of life. The strength of evolutionary imperatives is still
found today. Women who work in closed environments as a team often find
that their menstrual periods start to coincide such that all are fertile at
the same time. It has been postulated that this benefited the females by
allowing them to copulate with as many males as possible without revealing
who the father of the offspring was, thereby eliciting as much benefit from
food, shelter, etc. from the group’s males as possible. This spurred the
males in the society to provide as much protein and protection as possible
as none could be sure which carried their genes, therefore, they had to
protect and care for all to be sure their genes were passed to the next
generation. Further, it benefited the group by having all the females
pregnant at once, delivering closely together, thereby reducing their risks
of predation during the riskiest periods (birth). Furthermore, it allowed
the females to get back to their prime duty–providing the lion’s share (no
pun intended) of the root and fruit crops that sustained the group, while
men hunted, and basically sat around and scratched their butts.

So, as good as your column was, I think it wasn’t as well balanced as it
could be. I think you should return to this question, but include the
paleoanthropological evidence, the paleoenvironmental evidence, the fossil
evidence (and there is some–re:" Lucy) the paleogenetic evidence, and some
of the evolutionary anthropological evidence. All of this can be done from
the web. Authors to look at are Richard Klein, Chris Stringer, Milton
Walpoff, Paul Mellars, Andrew Cramer, Lovejoy, and others that you can get
right off the web. I also think I won’t be the only paleoanthropologist you
hear from. Debates are our life’s blood. Besides, its the only thing that
keeps us employed!!!
Aloha,

Wendy

35

There was a 57-year old one, though! Close enough!

As for any theory about older women not “surviving” pregnancy contributing to evolution… by that age they probably already had reproduced and passed on their genes. And plenty of young women didn’t survive pregnancy either.

36

What you have said certainly seems true in my family. My mother and both of my grandmothers began menopause at the same age I did: 42.

By the way, although I had a horrible PERI-menopause (yes, this is a recognized stage of a woman’s life!), I breezed through the “real thing.” Nonetheless, I often used to think to myself, “Whay does it have to be menopause? Why can’t it just be menoHALT?!!” :rolleyes:

37

Sigh. OK, here’s evidence of the reason we don’t like to have people pull up old threads (as Principessa pulled this one). The last post before she did was almost two years ago. JillGat, lamentably, no longer posts here, so she’ll most likely never see your comments, nancyflute, or be able to respond to them.

That’s not a criticism of you, nancy, but of Principessa who pulled this stunt several times.

We prefer that you start new threads rather than respond to very, very old comments.

38

I wouldn’t count JillGat out just yet–I found a thread of hers from August 16, 2004!

Though, of course, the point about bringing back old threads from the dead is a good one.

39

I think everyone’s been too harsh in criticizing Cecil on this answer. Perhaps he should’ve gone a bit farther back in time in referencing life expectancy, but the general point holds.

You’ve all been focused on American (4% of humans) or industrialized nation (still a minority) statistics. In most of the world the average person who makes it past infancy still has a rough time of it and is not likely to hit 65.

The huge spike in human population (people sticking around long enough in adulthood to produce multiple children who live) occured from the 19th century until now. I should hardly expect a process which evolved over 4-5 million years to be reversed in 150, especially as large parts of the world still aren’t posting the survival numbers of the industrialized nations.

40

Crandolph the whole point is that we aren’t focussing on American statistics. The point is that it doesn’t matter what the average age is in this context. If the average person who survives past infancy never makes it to 65 that doesn’t matter one bit so long as some do. The average wolf that makes it past infancy never makes it to the second year. However that doesn’t mean that wolves can enter menopause at 2 years of age, indeed exactly the opposite is true. The fewer females that survive the more vital it is that they continue breeding.

That is the point. Cecil is implying that the average wolf would have enough eggs for lifetime with only enough for oestrus events simply because few adult females survive past the first two such events. Of course that isn’t true. It doesn’t matter whether only 1% of females survive to any given age so long as they are able to breed at that age.

If the biological average human female lifespan were 45 there might be some logic I could follow in that statement, but so long as it remains a function of environment and chance it makes little sense.