Thin Is Out... By 2049

The average woman will be a touch heavier and shorter by 2049 according to a Yale University study on natural selection gleaned from two recent generations of women.

There is already plenty of controversy surrounding any talk about body weight and the effect of body image on our youth. It hit a new high in 2007 when negative publicity about the " boney apparitions" on the catwalk caused European designers to declare that super thin was now "out" and promised to keep a better eye on their models.

However, Diane von Furstenberg, president of the Council of Fashion Designers of America (CFDA), added fuel to the fire when she told a reporter that model weigh-ins in New York would happen "over my dead body."

...(women) are predicted to weigh about a kilogram more and be two centimeters shorter. They will also have lower blood pressure and cholesterol, will have babies up to five months earlier and go through menopause up to 10 months later, resulting in a longer child-bearing period.

As women have gotten heavier, models have gotten thinner and taller. Twenty-five years ago, the average female model weighed 8% less than the average American woman, according to researchers. Today, models weigh about 23% less than the average woman. The differences don't stop there. Models are usually about 5 feet 10 inches tall - a good five inches taller than they were 10 years ago - while a typical woman is about 5 feet 4 inches and weighs 155 pounds, according to a 2004 SizeUSA study.

In the U.S., only about 1% - about 10 million women and one million men - are anorexic, while nearly two-thirds of adults are overweight or obese, according to the U.S. Centers for Disease Control and Prevention.

This new report could polarize the differences between the two camps.

Writing in the Proceedings of the National Academy of Sciences, Sean G. Byars and three fellow researchers said traits can be predicted for the next generation of women based on factors with 2,000 women in the famous Framingham Heart Study which began in 1948.

Descendants of the women in the study are predicted to weigh about a kilogram more and be two centimeters shorter. They will also have lower blood pressure and cholesterol, will have babies up to five months earlier and go through menopause up to 10 months later, resulting in a longer child-bearing period.

“We found that natural selection is acting to cause slow, gradual evolutionary change,” the researchers said in the PNAS article. The study strongly disputes the contemporary and population notion that medicine-inspired longevity means that natural selection no longer applies.

The article goes on to state, “The reason is that traits that enable women to have children will continue to be subject to selection. As a first step, the Yale researchers measured the individual reproductive success of two generations of more than 2000 women who participated in the Framingham study and had reached menopause. They then surveyed the traits that conferred reproductive success. After adjusting for environmental factors such as income, education and lifestyle choices such as smoking, the researchers estimated the heritability of traits by applying correlations among all relatives. They also adjusted for the indirect effects of selection by measuring the impacts the traits have on each other – such as whether high blood pressure is correlated with lower or higher age of sexual maturity.”

Using statistical analysis, the researchers were able to determine which traits would be “conferred” on the future generation of women.

The study was funded by Yale University. Sean G. Byars, a post-doctoral researcher at Yale, was lead author of the paper. Researchers from the University of Pennsylvania and the Boston University School of Medicine contributed to the paper.

Citations:
Article on SmartPlanet (.com) entitled "Women predicted to be heavier and shorter" by John Dodge, published Nov. 2, 2009
Natural selection in a contemporary human population by Sean G. Byars, Douglas Ewbank, Diddahally R. Govindaraju, and Stephen C. Stearns published Oct. 19, 2009, in the Proceedings of National Academy of Sciences of the United States of America
Science & Engineering | Yale Bulletin entitled Evolution’s Path May Lead To Shorter, Stouter Women Who Give Birth Earlier published: Oct. 19, 2009
Newsweek Web Exclusive article entitled "Weighty Matters: We know that the trend toward super-thin models is pushing some of them to go on potentially deadly diets. What's it doing to the rest of us?" by Jessica Bennett, Sarah Childress & Susanna Schrobsdorff published Feb. 8, 2007, with updates on Feb. 20, 2008
Framingham Heart Study (.org)
The Origin of the Species, Charles Darwin

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