Please create an account to participate in the Slashdot moderation system


Forgot your password?
Biotech Science

Evolution's Path May Lead To Shorter, Heavier Women 411

Hugh Pickens writes "Yale University researchers believe that if evolutionary pressures of sexual selection and reproductive fitness continue for another 10 generations, the trends detected in their study may mean that the average woman in 2409 AD will be 2 cm shorter, 1 kg heavier, will bear her first child five months earlier, and enter menopause 10 months later. 'There is this idea that because medicine has been so good at reducing mortality rates, that means that natural selection is no longer operating in humans,' says Stephen Stearns of Yale University. 'That's just plain false.' Stearns and his team studied the medical histories of 14,000 residents of the Massachusetts town of Framingham, using medical data from a study going back to 1948 spanning three generations, and found that shorter, heavier women had more children than lighter, taller ones. Women with lower blood pressure and cholesterol were also more likely to have large families as were women who gave birth early or had a late menopause. More importantly, these traits are then passed on to their daughters, who also, on average, had more children. The study has not determined why these factors are linked to reproductive success, but it is likely that they indicate genetic, rather than environmental, effects. 'The evolution that's going on in the Framingham women is like average rates of evolution measured in other plants and animals,' says Stearns. 'These results place humans in the medium-to-slow end of the range of rates observed for other living things.'"
This discussion has been archived. No new comments can be posted.

Evolution's Path May Lead To Shorter, Heavier Women

Comments Filter:
  • by Baron_Yam ( 643147 ) on Sunday November 01, 2009 @09:51AM (#29941289)

    I doubt it. It probably reflects the fact that skinny women are less fit hosts for a fetus than heavier women. At some point, you run into high weight causing health issues that also make the woman a less fit incubator.

    Earlier maturity and later menopause extend the fertility period (duh)... in times past women needed more time to build up a healthy body to have children, and there was no genetic point in delaying menopause since pregnancies towards the end of female fertility were less likely to be viable. Modern medicine and diet are probably the enabler here, making girls healthy and heavy enough quickly enough to bear children when younger without significant risk of death, and making a higher percentage of near-menopause pregnacies successful.

  • by maxume ( 22995 ) on Sunday November 01, 2009 @10:00AM (#29941331)

    But social factors have at least some roots in genetics (blah blah blah nature vs nurture, well guess what, it isn't 100% of either one).

    Also, reproductive rates over 2 or 3 generations may not be particularly meaningful over the long term (if those people are dying substantially faster or whatever).

    (read the summary carefully, 1 kg and 2 cm isn't much to worry about, there will still be plenty of taller and leaner women after those changes)

  • by Colonel Korn ( 1258968 ) on Sunday November 01, 2009 @10:11AM (#29941385)

    Framingham is not America and America is not the world. While this report might hold true for a statistically insignificant group in one country, it tells us nothing about human evolution over the whole planet.

    The traits described probably have more to do with proximity to the local McDonalds, than anythiing about "survival of the fa^Hittest"

    Only blame the summary. Stearns made no such generalization.

  • by dkleinsc ( 563838 ) on Sunday November 01, 2009 @10:14AM (#29941403) Homepage

    Reproductive selection will always operate, it is just that the ''selection criteria'' may change, physical fitness may no longer be so important, supplanted by taking advantage of social security/... to enable them to have more children than they can support by the ''sweat of their own brows'', the government picks up the bill.

    To quote Monty Python: "Look at them bloody Catholics, filling up the bloody world with children they can't afford to bloody feed." At least, I assume that's what you were referring to.

    But seriously, the idea of a "welfare queen" is a myth (and typically a racist one at that). The vast majority of welfare recipients are trying to work, are unable to, but find work within about 2 years. Among other things, the per-child benefit that is given via WIC, TANF, and food stamps doesn't completely cover the cost of having the extra child, so having more kids makes even welfare recipients poorer.

  • by Baron_Yam ( 643147 ) on Sunday November 01, 2009 @10:26AM (#29941453)

    Any GP or OB/GYN will tell you that there is a minimum percentage of body fat below which a woman won't even menstruate.

    They'll also tell you a woman should gain some weight during pregnancy, and that generally speaking the outcome of the pregnancy is better if a certain amount of weight is gained (unless the woman is already overweight, of course).

    Again, I don't think they're saying thinner = bad, I think they're saying the population is shifting towards the optimum range. Skinny women have less, and less healthy children on average, so the average weight is rising by a small amount as they're outbred by heavier women.

    There will be an upper limit to this effect as well - morbid obesity is not a good thing for getting or being pregnant, either.

  • Re:Alrighty Then (Score:1, Informative)

    by Anonymous Coward on Sunday November 01, 2009 @11:33AM (#29941901)

    That's a better explanation but it's not quite there. There are various types of Creationists/ID proponents -- not all of them Theistic. Some are Deistic.

    There are the following extremes with many shades between them:

    * People who believe that the earth is only 6000 years old. Why, I don't know. It's not dogma and never has been until recently in the US. Nowhere in the Bible does it say that the world is 6000 years old. All that it says is that the earth is *at minimum* 6000 years old and that there is a beginning of the universe.

    * 6 day creationists with an indefinite gap on the first day since it's never stated that the universe except earth was created in 1 day, only that God created everything. Again, this is mostly a US-centric view.

    * Day age creationists that believe the Biblical doctrine that God created everything, both the Bible and the universe so both must be consistent. If evolution is true, then Natural Selection is either guided by God or each new species is a special act of creation and evolution is simply an intraspecies adaptive mechanism.

    * Deistic/Hyper-Calvinist creationists that believe that God wrote the equations at the start of creation so that life with specified characteristics would inevitably occurred. Once that life occurred, God (if not Deistic) would then breath a soul into the first person.

    ID proponents tend to be one of the later two.

  • by Anonymous Coward on Sunday November 01, 2009 @11:43AM (#29941973)
    pardon me but your bigotry is showing

    people in lower social and economic classes have always reproduced more than the wealthy and middle class, for as long as there has been money and class. This has nothing at all to do with ethnicity, in previous generations it was the irish, italians, chinese, now it's hispanic immigrants in that role, but it is economic situation that is the controlling factor.
  • by forand ( 530402 ) on Sunday November 01, 2009 @01:20PM (#29942496) Homepage
    The variations that are being discussed in the article are not all all outside the variations already observed in humans over that period of time. While our DNA has been reasonably set for ten thousand generations, as you say, the dominance of certain phenotypes varies with time and location. For instance many humans have dramatically different skin tones and facial structures. Variations similar to what is discussed in the article have occurred in a variety of places of the past 60 years (although mostly attributable to dietary changes).

    Finally, the sample size used was 14000 (if the an above post is correct) and they are discussing evolutionary pressures which cause one group to be more able to produce offspring than others, thus the results may hold for a much larger sample (assuming that the phenotypes correlate with the underlying cause which may not be valid but could reasonably be).
  • by Anonymous Coward on Sunday November 01, 2009 @01:25PM (#29942528)
    It's an indisputable fact that people with lower incomes tend to have more children []. And the GP didn't say anything about welfare queens or politics; he simple stated the fact that the many transfer programs in this country mean being unable or unwilling to provide for your offspring no longer limits your reproductive potential.
  • by harvey the nerd ( 582806 ) on Sunday November 01, 2009 @02:11PM (#29942780)
    "Welfare queens" are not a myth, they are history. TANF was developed and passed in 1996 specifically to replace AFDC for this reason, after peaking in about the 1970s when some states began to tighten up their rules. Many bricks form the social net, also there are income credits (EIC), Social Security (for deceased/disabled spouses) and still various forms of charity.

    Also careful shopping can reduce food cost far below average. I've been hiring 2-3 low wage earners/week this year and I notice they spend far more on junk (20 oz branded soda, Cheetos, etc) alone than I spend on half or more of my at home meals (e.g. carved ham, $1.29/lb, two eggs, @$.78-1.10/doz, toast, tomato, $1.99/gal milk/tea and vitamin, 3 cents). Chicken, $0.78/ lb, and fresh produce are usually cheaper, too. I am sure that I am a more careful shopper, although I just pick up staples and specials at their lowest cost place in my part of town, passing by.

    Even today, I am not so sure about welfare being below the incremental cost per child for careful shoppers (e.g. $3/day for healthy food, thrift shop or handed down clothes, and often incrementally free housing.)
  • by Maxo-Texas ( 864189 ) on Sunday November 01, 2009 @03:49PM (#29943518)

    Your facts are less correct than they were 50 years ago. []
    "The movement of families up and down the economic ladder is the promise that lies at the heart of the American dream. But it does not seem to be happening quite as often as it used to." []
    Eighty percent of Americans still believe it's possible to pull yourself up by the proverbial bootstraps. That's according to a New York Times poll reported last week, but a recent mobility study suggests the American Dream may be more style than substance. []
    Upper nonmanual occupations have the highest level of occupational inheritance. [3] []
    As his father did before him, Hurd attended the Browning School - a prestigious all-boys school where classmate Jamie Dimon, now CEO of J.P. Morgan Chase, remembers seventh-grader Hurd as a good basketball player

    The wealthy own the media and push the "you could be wealthy!" idea hard. It helps keep the lower class folks voting against their own self interests. It's why the wizard of wall street pays a lower tax rate on his monumental earnings than his secretary pays on her salary.

    There is a tiny chance you will break into the wealthy classes. But, for the most part, they pass the good jobs down to their own. Just look at the way hollywood has been taken over by 2nd and 3rd generation actors. CEO jobs are less obvious but essentially the same.

    Any idiot can bankrupt themselves-- but it takes a lot more than simple hard work to get into the executive class.

  • by negRo_slim ( 636783 ) <> on Sunday November 01, 2009 @04:40PM (#29944014) Homepage

    The average Caucasian height was about the same 300 years ago.

    According to this [], the average United States citizen has gained 5cm since the mid 19th century.

  • by cayenne8 ( 626475 ) on Sunday November 01, 2009 @07:28PM (#29945390) Homepage Journal
    "The anorexic ones don't reproduce."

    I"m not talking about unhealthy thin...but, fit and healthy thing...something like Jennifer Anniston, I mean that lady is 40 and STILL looking hot...or something along the body fitness of Adriana Lima (I think that's her name) of Victoria Secrets. These women are very healthy, no pudging bellies, no cottage cheese thighs...something that looks good with their midriffs showing.

    There's a difference between being fit and being anorexic.

  • by shawb ( 16347 ) on Monday November 02, 2009 @12:01AM (#29947114)
    I think GP meant that 300 years ago the average Caucasian height was about the same as that of other races... it has only been since the agricultural and industrial revolutions that our average height has increased. I believe a similar increase in height is currently occurring in China and other Asian countries as the adopt a more occidental style of diet with higher protein levels.
  • by Maxo-Texas ( 864189 ) on Monday November 02, 2009 @01:07AM (#29947504)

    I guess I left out some words.

    Here's a good article... []
    where it says, in part:
    The average height for an early 17th-century English man was approximately 5' 6". For 17th-century English women, it was about 5' ½". While average heights in England remained virtually unchanged in the 17th and 18th centuries, American colonists grew taller. Averages for modern Americans are just over 5' 9" for men, and about 5' 3 ¾" for women. The main reasons for this difference are improved nutrition, notably increased consumption of meat and milk, and antibiotics.

    For modern white Americans, the average stature for males is 69.1", or just over 5' 9", and for women, 63.7", or about 5' 3 ¾".


    Some chinese are tall now. As their food quality improves, I think their average height will improve.

    It looks like the japanese have increased from 5'5" to 5'7" since WWII.

    There was an article a few months ago that some group of humans have stopped getting taller (one of the nordic countries I think) so they may have found the limit of nutrition effects.

The other line moves faster.