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Imadethisupwithnoforethought's avatar

Human Females are unique among all mammalians. Why do you think the ability to hide fertile time periods evolved in human women?

Asked by Imadethisupwithnoforethought (14270 points ) April 6th, 2014

Why do you think the ability to hide fertile time periods evolved in human women?

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44 Answers

Darth_Algar's avatar

Ummm, what?

Imadethisupwithnoforethought's avatar

Females of most mammal species advertise fertility to males with visual behavioral cues, pheromones, or both.[6] This period of advertised fertility is known as oestrus, “estrus” or heat.[6] In species that experience estrus, females are generally only receptive to copulation while they are in heat[6] (dolphins are an exception).[7]

from wikipedia

Adirondackwannabe's avatar

If you really get in tune with a woman they don’t hide it, it’s just very subtle.

Jonesn4burgers's avatar

It is part of the natural selection process. Various species have their own way of selecting partners. Humans can select their partners, and with care, their timing.
Nature is still working on the actual effectiveness of the timing part.

Imadethisupwithnoforethought's avatar

@Jonesn4burgers so you think human females wish to hide their timing?

Jonesn4burgers's avatar

Females of many species choose their mate to produce the best possible offspring. With humans, there is the opportunity to not only choose the who, but also the when mating will produce a child. These things are what nature has evolved within us, but part of that is the evolution of intellect. When we fully understand that science, and our understanding is a part of the evolutionary process, and use is wisely, we will be able to make the human species top notch. That doesn’t mean picking blonde hair, green eyes, and shoe size, but healthy attributes. It also includes using our intellect to control population so we don’t occupy ourselves right out of our resources.

dappled_leaves's avatar

Hey, dolphins do it, too. From Wikipedia:

“Another, more recent, hypothesis is that concealed ovulation is an adaptation in response to a promiscuous mating system, similar to that of our closest evolutionary relatives, bonobos and chimpanzees. The theory is that concealed ovulation evolved in women to lessen paternity certainty, which would both lessen the chances of infanticide (as a father is less likely to kill offspring that might be his), and potentially increase the number of men motivated to assist her in caring for her offspring (partible paternity). This is supported by the fact that all other mammals with concealed ovulation, such as dolphins and gray langurs, are promiscuous, and that the only other ape species that have multi-male communities, as humans do, are promiscuous.”

Seek's avatar

Hm.

When I’m ovulating, I smell different. I know I do. And I can see changes in my skin as well. I put on a little bit of weight, and there are other changes as well.

Perhaps human males have forgotten how to read the signs, or our modern culture of scent-masking, cosmetics, and clothing are disguising them.

Imadethisupwithnoforethought's avatar

@Seek Do you find that you are doing this regardless of your relationship status, or does it concentrate?

GloPro's avatar

Humans have an extremely developed cerebral cortex. Responsible for memory, communication, and thinking, it is possible that human females consciously choose to be discrete because intelligence is a driving her selection of a suitable mate.

JLeslie's avatar

When I ovulate my husband usually comes after me. I don’t think he knows why. We have had months where we could not have sex for health reasons, and we would get rather asexual in general, but that time of the month he would reach for me.

It’s true though that it is less obvious in human females than other animals. A lot of women are not in tune at all. I can’t understand it.

It seems to me human beings have sex not only to reproduce, but also as a way of connecting with each other and enjoying each other. We use our brains as part of sex, it is not just some primal need to reproduce. By allowing women to want sexual intercourse even when they cannot become pregnant it enhances the connection between partners. I wonder if animals that are like to mate for life have more intimate contact even outside of fertile times? That would be interesting to know.

Seek's avatar

@Imadethisupwithnoforethought – That’s going back a ways… I’ve been with my husband since I was 20 – so, eight years – and have no relationship history prior to him. I seem to remember fluctuations in body scent in high school as well, but I couldn’t say for certain whether they were ovulation or pre-menstrual. I simply don’t remember and don’t want to succumb to possible confirmation bias.

Imadethisupwithnoforethought's avatar

@Seek It seems to be a fact.

My question was, what purpose is it serving?

Seek's avatar

I don’t know. Ask me 100,000 years ago.

hearkat's avatar

It’s not a conscious decision that we make to “hide” it each month.

The practice and purpose most likely evolved around cultural practices beginning with those that ostracized women during menstruation, and then those that deemed sex ‘dirty’. We reach an age of fertility long before we are culturally ready to procreate, so the adolescent females not ready to marry are not supposed to advertise that their eggs are ripe. As society has become more complex, there are things that need to be tended to. I can’t take a week out of every four off because there’s blood pouring out of my crotch.

Besides, with humans, ovulation can even occur during menses, so there really isn’t a way to know for sure when we are actually fertile. Some are more regular than others, and I have found that the signs were more obvious the older I’ve gotten, but I couldn’t really say with certainty whether it is because I know my body better, or whether it’s because my body is changing. Most likely, it’s a bit of both.

As we’ve developed culturally, we also aren’t driven by the need to propagate the species the way animals are. Our society expects us to be responsible about when and with whom we reproduce. Some cultures allow couples only one or two children; very few modern cultures support the idea of having a dozen or more children. It’s a product of human civilization.

Judi's avatar

Were you inspired by this article I saw on Facebook today?

JLeslie's avatar

@hearkat The chance of ovulation during menstruation would be extremely rare. Let’s say a woman has her period 8 days (which is rather long) if she had good young eggs the chance she would ovulate that early, like I said, extremely rare. Ovulating day 8 would be a 20–22 day cycle with a normal luteal phase. Most women don’t have their period for 8 days, although mine was 7 for almost 30 years. Now it is a little shorter.

hearkat's avatar

@JLeslie – I only said that it can happen – to illustrate the somewhat unpredictable nature of it – as part of the other points I was making overall. What is your point as it relates to this topic presented by the OP?

JLeslie's avatar

@hearkat It’s just so rare. The person who might ovulate while menstruating, probably is not fertile. If we define fertile as the time that having sex can cause a pregnancy, then yes, the final days of a period you might still get pregnant, because the sperm live, not because you ovulated day 6. Maybe that is what you are thinking about? That it is advised to always use protection against pregnancy, even during our periods.

Actually, just thinking about that, since human women the majority of the time only pop me egg out, maybe that is why we want sex more than just the time of ovulation? Because having sex before the egg pops helps the chances of a sperm meeting the egg. Other mammals have litters. I wonder it animals like cows and horses that also have singletons have very different sex practices than cats or dogs that have multiple babies at once?

JLeslie's avatar

Edit: should be pop one egg out. Not pop me egg out. Also, I can’t imagine an egg ripening in 4 or 5 days. Even what I wrote about a woman who ovulates really early probably isn’t fertile, the more I think about it I don’t see how it happens. I can’t imagine eggs ripening within 7 days. On super fertility drugs it takes longer.

hearkat's avatar

@JLeslie – In the case of fraternal twins or other non-IVF multiple births, women “pop out” two or more eggs. Some women, including myself, ovulate and get pregnant while taking birth control pills. Sure, these occurrences are rare, but they illustrate the unpredictability of human ovulation as it relates to the points I was making relevant to the discussion of why we don’t advertise being “in heat” as posed in the OP – we can’t always tell when we’re ovulating.

JLeslie's avatar

@hearkat I know women can pop out more than one egg, but the majority of the time it is one, in contrast to cats that can easily have 6 fraternal kitties.

I agree a woman who ovulates while menstruating would have fewer cues she is ovulating, especially the change in discharge, which I think is one of the more obvious signs if she doesn’t get a pain on her side. The pain on my side was very clear when I was younger, but that stopped as I got into my 30’s.

I’d be curious to know how often it happens. I’m not asking you to research it or prove, just curiosity.

I think we don’t advertise we are in heat and maybe are less in touch with it, because for centuries women have been trying to control their fertility. We spend most of our time trying to not get pregnant.

Stinley's avatar

I read about humans being socially monogamous but otherwise not so much. Hiding ovulation makes covering up who the father is so much easier.

Imadethisupwithnoforethought's avatar

@Judi Actually watching Cosmos with my kids. Talking about evolution all day.

JLeslie's avatar

@Stinley Some woman are not hiding it, they are completely oblivious of it. Do you think being oblivious is a side effect of trying to hide it over thousands of years? Interesting take I had not thought of.

Judi's avatar

@Imadethisupwithnoforethought , funny the theme would be so prefer ant in one day. I thought that article was interesting, how women’s menstruation evolved.

dappled_leaves's avatar

@JLeslie Concealed ovulation cannot be the effect of “trying to hide it” over a long period. What you are describing there is a kind of Lamarckian evolution – like the notion that a giraffes’ necks becoming longer because they strained to reach tall trees. What happens in natural selection is that within a population, there is wide variation in the trait (some females with concealed ovulation, some with overt ovulation), and there is, on average, over large numbers and long timescales, a shift in the trait towards concealed ovulation due to differential reproductive success.

JLeslie's avatar

@dappled_leaves I understand that. The concealed ovulation could lead to more babies, hence producing more women with concealed ovulation. I’m not saying I really believe that is why ovulation isn’t overtly obvious, but it could be a reason why. When men have sex with women they can have wishful thinking she won’t get pregnant, because he can’t be sure what is going on with her hormonally and her ripening egg. I don’t know when mankind decided they would have sex with people they don’t want to have a baby with. A lot of people in modern society do that.

Ironically, women are more aroused during ovulation and men seem to be more attracted to women who are ovulating, even if they are not conscious of it. So a chance sexual encounter is more likely to happen during ovulation.

The tricky part is women who want to get pregnant sometimes can’t figure out the right day because it isn’t obvious to so many women when they are ovulating.

dappled_leaves's avatar

@JLeslie “I don’t know when mankind decided they would have sex with people they don’t want to have a baby with”

No expert on behaviour here, but I don’t agree with the premise that mankind particularly “decided” this. I think that the earliest form of man would have been acting on pure, instinctive desire. The traits that make a mate sexually attractive followed from differential reproductive success – I find that woman sexy, so I have sex with her. Baby results, carrying sexy genes forward. Sexy offspring also attract mates, carrying sexy genes forward again. If there was a “decision point”, it might have been following the realization that baby follows sex. Once that realization occurs, when and with whom to have sex becomes partly a social or political decision. But I think that having sex purely for desire must be the default state. We have to work to resist that when it’s against our best interests.

So I guess it comes down to a chicken-and-egg question: at what point in our evolution did we become aware that sex leads to babies? It’s entirely possible that this happened before we were even human.

canidmajor's avatar

Maybe it’s more about the receptivity of the female than the impregnability factor. If a male responds to the signals of a female being receptive, he may stay closer to her to continue his attempts to impregnate her. An increase in the size of the group/pack/community increases the probability that said grouping will survive and thrive.

JLeslie's avatar

@dappled_leaves I think our ability to think logically screws it up a little. Our brains probably have more inhibition than other animals, and more complex thoughts, that interfere with us just having sex because we feel turned on by someone. We have all sorts of concerns and social norms that we need to juggle that affect whether we just chase down the pretty girl or guy.

I should mention that when I was on the pill I still was plenty horny and had plenty of men wanting to have sex with me. Ovulation was surpressed, but it didn’t matter.

deni's avatar

If a woman lived in the wild today with no pads, tampons, or soap, it would most definitely not be hidden. We hide it cause we pretend we aren’t animals. Don’t get me wrong, I’m glad women aren’t bleeding all over the place. But I know the smell of my own period blood, and i don’t believe we have “evolved” to hide it. We just do so with man-made items.

dappled_leaves's avatar

@deni Agreed, but I’m going to guess that even if we were naked in the woods, our mates wouldn’t be able to sense our ovulation. That’s the event that’s concealed.

rojo's avatar

Pawlowski hypothesizes that change to bipedalism in early hominids changed both the position of female genitals and the line of vision of males. Since males could no longer constantly see the female genitals, swelling of them during estrus as a mode of signaling would have become useless.

Bazzinga!

Stinley's avatar

@rojo but if it were useful in evolutionary terms we would have developed another way to indicate that we were fertile. Like, I dunno, our face lips swell and become red or boobs get much bigger. Something.

JLeslie's avatar

@dappled_leaves Not exactly. The Jews don’t let husband and wife have sex during a woman’s period partly to increase their likelihood to get pregnant. Or, that was their theory without hard science to prove how the woman’s cycle actually works. Now that even they know how it works through science, they still see it that after the waiting, husband and wife are more likely to have sex during or just before the most fertile days.

Maybe even before the Jews people had an idea about most fertile times. They possibly saw some sort of pattern. @deni made a great point about how we conceal many things artificially. We conceal how we smell with perfume too. Although, the pheromones are not actually smell they are a hormonal or chemical signals. I think that is likely what my husband is picking up on.

rojo's avatar

@Stinley Perhaps, then, we could surmise that knowing when the female was fertile either was not that necessary a trait, or rather that bipedalism was more important, or that concealing ovulation was, for some reason, more important.

Now the boobs getting larger, that is another discussion for another question.

Stinley's avatar

@rojo go on then, I’ll join in if you ask…

deni's avatar

@dappled_leaves True. Well, how do some other female mammals signal when they are ovulating? I am in the dark on that topic.

dappled_leaves's avatar

@deni Per the Wiki article I linked above, “Some examples of such changes are swelling and redness of the genitalia in baboons and bonobos Pan paniscus, and pheromone release in the feline family.”

Imadethisupwithnoforethought's avatar

The bottom line… Human females have evolved to not show when they are most fertile to observers. Some would assume this is an adaptation that fools their pair bond.

dappled_leaves's avatar

@Imadethisupwithnoforethought Well, first – it’s not like it was a conscious decision. Second… if your “pair bond” is likely to periodically kill your children, maybe that’s a good thing.

Needless to say, none of this matters to humans anymore. We have conscious choice, and defy our own biological instincts all the time.

Imadethisupwithnoforethought's avatar

@dappled_leaves I am asking you what was the unconscious decision?

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