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This is Scientific American ― 60-Second Science. I'm Christopher Intagliata.
In Latin America, Native Americans, Africans, and Europeans have intermixed for centuries.
So, a few years back, researchers sought to learn more about the ancestry of more than 7,300 people from Brazil, Chile, Colombia, Mexico and Peru.
The volunteers provided DNA samples. And they also answered the question: what do you think your background is?
Turns out that what they thought―that is, their predicted ancestry―
told a different story than their genes did―with skin color a key factor.
"Their predicted ancestry is actually very well correlated with their skin color,
but poorly correlated with their actual genetic ancestry.
So that showed us people are actually trying to predict their whole ancestry by just looking at their skin color,
which is a pretty crude thing to do, but that's how the attitude is in Latin America."
Kaustubh Adhikari, who studies human genetics at University College London.
In particular, lighter-skinned volunteers tended to overestimate their European ancestry
whereas darker-skinned subjects overestimated their Native American or African backgrounds.
Now a new study by Adhikari and his colleagues offers a reason for the mismatch.
The skin color data and the DNA sequences led the researchers to identify a genetic variant for lighter skin that arose in Asia 20- to 30-thousand years ago.
That event appears to be independent of the evolution of lighter skin in Europe.
这里是科学美国人――60秒科学。我是克里斯托弗・因塔利亚塔。
数个世纪以来,美洲原住民、非洲人和欧洲人在拉丁美洲混合居住。
因此,几年前,研究人设法进一步了解来自巴西、智利、哥伦比亚、墨西哥和秘鲁的7300多人的血统。
志愿者提供了DNA样本。他们也回答了这个问题:你认为自己的血统背景是什么样的?
结果表明,他们的想法――也就是他们预想的血统――
与其基因得出的结果并不一致――这里以肤色为关键因素。
“他们预想的血统实际上与其肤色密切相关,
但与他们真正的遗传血统相差甚远。
因此,这表明人们实际上是仅看肤色来预测自己的整个血统,
这是非常鲁莽的做法,但这就是拉丁美洲人的态度。”
在伦敦大学学院研究人类基因的考斯塔布・阿德希卡里说到。
特别是,肤色较浅的志愿者往往会高估自己的欧洲血统,
而肤色较深的志愿者则会高估自己的美洲原住民或非洲背景。
现在,阿德希卡里及其同事进行的一项新研究提出了这种错配的原因。
依据肤色数据和DNA序列,研究人员找到了一种导致较浅肤色的基因变体,这种变体在2万到3万年前出现。
这一事件似乎与欧洲较浅肤色的进化无关。
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