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The Geometry of Fertility

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The Economist (May 6) has a most interesting article on female body shape and fertility: it seems that girls with small waists and big boobs are three times more likely to get pregnant at any given time than slender babes.

The reason: busty babes have much higher levels of the hormones progesterone and 17-b-estrodiol, whose concentrations are directly proportional to a woman’s fertility.

Here’s the article:
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Gentlemen may or may not prefer blondes.

But, in rich countries at least, they do seem to prefer women with hour-glass figures. There have been various ideas about why this is so. The politically correct suggest that it is mere fashion – and point to evidence that tastes are sometimes different in poorer societies.

Those of a more biologically deterministic frame of mind suggest that wide hips, relative to waist size, are good for child bearing, and that large breasts deliver more milk.

What has not been widely suggested is that women with classic figures are simply more fertile.

But that is what Grazyna Jasienska and her colleagues at Harvard University hypothesize in the latest edition of the Proceedings of the Royal Society.

They have found that in women of child-bearing age, the levels of two hormones known to be associated with fertility are, as it were, geometry – dependent.

Dr. Jasienska measured the vital statistics of 119 women aged between 24 and 37.

She also took saliva samples from them over a whole menstrual cycle.

She then divided her sample into four categories – a combination of narrow or broad waist-to-hip ratio with small or large breast-size – and looked for statistically significant differences between them in the levels of progesterone and 17-b-estrodiol, two hormones whose concentrations are known to be related to a woman’s fertility.

The research by Dr. Jasienska and colleagues is published in the Proceedings of the Royal Society.

In the case of progesterone, both groups of narrow-waisted women had high hormone levels.

In that of 17-b-estrodiol, those with narrow waists and large breasts had elevated levels – and that level was particularly high at the time of ovulation.

Indeed, it was so high that Dr. Jasienska estimates such women are three times as likely as the others to become pregnant on any given occasion. In evolutionary terms that makes them very desirable mates indeed.

Why a woman’s shape should reflect her hormone levels is not yet clear.

That is one obvious next question to investigate. Another might be to put the boot on the other foot, and ask whether men with beer guts are less potent than their hunkier fellows.

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  • http://www.gwbush.blogspot.com RJ Elliott

    “Another might be to put the boot on the other foot, and ask whether men with beer guts are less potent than their hunkier fellows.”

    Clearly this is the case. “Hunky” types are more likely to have higher levels of testosterone than “Chunky” types. More testosterone = a greater chance of both wanting to engage in intercourse and being able to do so.

    Our society is still bound by the rules of the caveman. Tall, strong men are better able to fend off predators and other potential males, and are thus more likely to be able to provide safety and comfort for their female mates. They are also more likely to carry “good” genes, have an adequate quantity of testosterone, and be hung like rhinos.

    Short, flabby men are less likely to be able to fend of predators and other males, and are less likely to be carrying “good” genes and have high levels of testosterone. And penis size is (in general) directly correlated to the size (i.e. height) of the male…

    No wonder women tend to seek out tall, muscular, confident men. And shun short, flabby, and weak men.

    (For those who dispute this basic fact of life: Who got more pussy in high school: The Computer Club and Band members, or the Basketball and Football teams?)

  • duane

    Who got more pussy in high school…

    The guys in rock bands. Heh.

  • http://www.gwbush.blogspot.com RJ Elliott

    And they tend to be confident, tall, and thin. ;-]

  • http://www.bhwblog.com bhw

    RJ, I’m a-scared of whoever taught you biology.

    For every sweeping generalization, there are, of course, always exceptions.

    I am a human stick figure with small mammalian protruberances, and yet it took me a total of three months to conceive both of my children. Fertile I am!

  • http://www.gwbush.blogspot.com RJ Elliott

    BHW:

    Do you understand that empirical evidence is generally viewed as more worthy of serious debate than anecdotal evidence?

  • http://www.bhwblog.com bhw

    They are also more likely to carry “good” genes, have an adequate quantity of testosterone, and be hung like rhinos.

    Is this the empirical evidence of which you speak?

  • http://www.gwbush.blogspot.com RJ Elliott

    BHW:

    I suggest you do some research. Tall men tend to have larger “things” than short men. This is a fact.

    What’s your beef? Are you a shortie? ;-P

  • http://www.bhwblog.com bhw

    Also, from the article:

    Why a woman’s shape should reflect her hormone levels is not yet clear.

    Did the article’s author ever consider that it’s the other way around, that it’s the hormone levels that reflect — a.k.a. result in — the shape?

    Duh.

    And I breastfed both of my children for a year. With my itty-bitty-titty-committee breasts. Everything I have ever read about breastfeeding says that there is NO correlation between breast size and the ability to supply milk.

    Another duh.

  • sheri

    And the question is…..how tall is RJ Elliot.

  • http://macaronies.blogspot.com Mac Diva

    I also notice that women’s bodies can change over time. I had ‘barely a B’ until I was 30 or so. (Even wore a bra named that.) Then, I sprang noticeable protuberances. They are irritating, ruining the lines of my blouses and dresses, and forcing mismatches when I buy separates. I wish they would go away.

  • http://www.bhwblog.com bhw

    LOL!

  • http://macaronies.blogspot.com Mac Diva

    I’ve also noticed that women’s bodies can change over time. I had ‘barely a B’ until I was 30 or so. (Even wore a bra named that.) Then, I sprang noticeable protuberances. They are irritating, ruining the lines of my blouses and dresses, and forcing mismatches when I buy separates. And, too many men look at my chest instead of my face. I wish they would go away.

  • http://www.bhwblog.com bhw

    Your protruberances or the men?

  • http://macaronies.blogspot.com Mac Diva

    Both. LOL!

    I never wanted large breasts. Some women pay thousands to get them. And, Mother Nature just up and imposes them on me. Too bad they are not transferable.

    Sorry about the double post. The server said it was stuck.

  • http://www.femininebeauty.info/ Erik Holland

    Although I am late in replying, I have reproduced the main data from the paper by Jasienska et al. here; scroll down for the data on the page linked to. Related to this study, those interested in how sex hormones subtly shape physical appearance can find some detailed information here.

  • keith

    RJ you’re full of crap. Tall guys get beat up by short guys all the time.

    Steve Mcqueen was the biggest action star of his time, and he was only 5’7.

    Some of the best soccer players in the world are short, and run “circles” around tall guys.

    You’re theories are WHACK.