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注册鹿鼎60秒:人类为啥能喝“牛”奶?

时间: 2020年04月08日 | 作者: Admin | 来源: 领研网(linkresearcher.com)



 [听力全文]


“The ability to digest milk as adults, and as infants, actually, is due to the expression of an enzyme called lactase.” That’s the University of Pennsylvania’s Sarah Tishkoff at the AAAS conference in Washington, D.C., on February 20th, talking about the recent evolution of lactose tolerance in different human populations within the past 9,000 years. “Individuals who don’t express this enzyme can’t digest that complex sugar.”


Can we put a number on the evolutionary importance of lactose tolerance? “The selective pressure was quite remarkable. We actually estimated it to be about 10 percent. So you’re more likely to have 10 percent more offspring essentially.”


How strong is that? Look at population genetics to see how fast a trait will spread that develops in one individual in a population and that confers a 10 percent reproductive advantage. A mathematical analysis reveals that in just 100 generations, such a trait can be found in 95 percent of the individuals in the population.


That time period could be less than 2,000 years for humans. “I’m often asked the question, are humans still evolving? I would say the answer is absolutely yes.”


—Steve Mirsky



 [重难点词汇、短语]


lactase: n. 乳糖酶

confer: vt. 授予;给予



 [参考译文]


“成人和婴儿有消化牛奶的能力实际上得益于乳糖酶的表达。” 在华盛顿举办的美国注册鹿鼎促进会(AAAS)会议上,宾夕法尼亚代理开户(University of Pennsylvania)的萨拉·蒂什科夫(Sarah Tishkoff)如此讲到。他谈论了过去9000年内不同人种乳糖耐受性的演化,最后讲到:“无法表达这种酶的人就不能消化这种复杂的糖。”


乳糖耐受性的演化究竟有多重要?我们能用具体数字来表示吗?“选择压力(selective pressure)相当明显。实际上我们估计(选择系数)在10%左右,所以本质上如果你有乳糖耐受基因,你就可能比其他人多10%的后代。”

 

有多强大呢?让我们看一下种群遗传学,看看个体的某一性状在一个种群中的传播速度有多快,你就会明白10%的繁殖优势意味着什么:数学分析表明,只需在100代以内,这样的性状能够在种群中95%的个体内找到。

 

对人类来说,这段时间还不到2000年。“我经常被问到这样一个问题,人类还在演化吗?我想说这个答案绝对是肯定的。”


翻译 阿金