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近期发表在美国《国家科学学会学报》上的一项研究报告显示，在人类进化过程中，女性将会变矮、体重会增加、身体会更健康，而且生育周期会更长。如果按照这项研究的趋势发展，到2409年的时候，女性的平均身高将会减少2厘米，体重增加1公斤，生育头胎的年龄将会提前5个月，而停经期将会推后10个月。这项研究是由耶鲁大学进化生物学教授史蒂芬•斯特恩斯组织进行的，他和他的研究小组对马萨诸塞州弗雷明汉镇1.4万居民中2238名已过生育年龄的女性医疗史进行研究，并测量了她们的身高、体重、胆固醇、血压以及其他指标。结果发现，身材矮小、体重较重的女性生的孩子比高个、苗条的女性要多；血压和胆固醇指标较低的女性多育的几率也较高。研究还发现，母亲的这些身体特质都会遗传给女儿，并由此影响到下一代的生育状况。
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New research at Yale University has provided the strongest evidence yet that humans are evolving – and suggests that women of the future will be shorter, heavier, and healthier, and will have children for longer. |
New research at Yale University has provided the strongest evidence yet that humans are evolving – and suggests that women of the future will be shorter, heavier, and healthier, and will have children for longer.
As medicine has allowed people who would previously have died young to live to childbearing age and beyond, many have assumed that natural selection no longer works on our species.
But Prof Stephen Stearns, the evolutionary biologist at Yale University behind the study, says: "That's just plain false."
While survival to reproductive age is no longer such a hurdle for humans, other evolutionary pressures – including sexual selection and reproductive fitness – are still working away in full force.
If the trends the research detected are representative and continue for another 10 generations, Prof Stearns says that the average woman in 2409AD will be 2cm (0.8in) shorter and 1kg (2lb 3oz) heavier, will bear her first child five months earlier, and enter the menopause 10 months later.
Prof 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 and spanning three generations.
It looked at 2,238 women past reproductive age – so that they had had all the children they were going to – and tested their height, weight, cholesterol, blood pressure, and other traits, to see if there was a correlation with the number of children they had borne.
It 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.
Women who gave birth early or had a late menopause were likely to have more children as well.
More importantly, however, these traits were 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. Prof Stearns’ team controlled for other factors, including social and cultural change.
He told New Scientist: "It's interesting that the underlying biological framework is still detectable beneath the culture."
Research suggesting humans are evolving has been carried out before, but this is believed to be the first that directly compares reproductive success of individuals with physiological changes.
The research is published in the Proceedings of the National Academy of Sciences journal.
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(Agencies)
（英语点津 Helen 编辑）
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