A comprehensive scan of the human genome finds that hundreds of our genes have undergone positive natural selection during the past 10,000 years of human evolution.

    Genes are the instructions organisms use to make proteins. They are encoded in genetic material, usually DNA, and some come in different versions, called “alleles." Positive natural selection occurs when one allele is favored over another due to changes in the environment.

    Researchers from the University of Chicago analyzed the genomes of 209 unrelated individuals from three distinct human populations: East Asians, Europeans and Yorubans from Nigeria. Each population contained roughly 250 positively selected genes; however, most of the affected genes differed depending on the group.

    “This study addresses the question 'Are humans still evolving?', and the answer is 'Absolutely,'" study team member Benjamin Voight said.

    The new study links genetic changes to major events in the history of our species.

    “There have been a lot of recent changes—the advent of agriculture, shifts in diet, new habitats, climatic changes—over the past 10,000 years," said Jonathan Pritchard, a human geneticist at the University of Chicago who led the study.

    The researchers also found positive selection in four pigment genes important for lighter skin in Europeans that were not known before. Scientists think humans evolved lighter skin in Europe as an adaptation to less sunlight.

    And in East Asians, they found strong evidence of positive selection in genes involved in the production of alcohol dehydrogenase (ADH), a protein necessary for breaking down alcohol. Many East Asians can't metabolize alcohol because they carry a mutation that prevents them from making ADH. The new finding suggests that the mutation may confer some currently unknown additional benefit.

    The study, which used data collected by the International HapMap Project, is detailed in the March 7 issue of the journal Public Library of Science-Biology.

    一次針對人類基因組的全面掃描顯示：在過去的一萬年中，人類體內(nèi)上百組基因仍在經(jīng)歷積極的自然選擇。

    基因是制造蛋白質(zhì)的指導(dǎo)性有機體。它們藏于遺傳物質(zhì)中，一般在脫氧核糖核酸中，也有的在等位基因中。當一個等位基因比其他的更能適應(yīng)環(huán)境時，積極的自然選擇就會發(fā)生作用。

    芝加哥大學的研究人員從東亞人、歐洲人和尼日利亞的約魯巴人這三種截然不同的人種身上提取基因并進行分析。每種人體內(nèi)都含有大約250組被積極選擇的基因；但是每種人基因進化的具體情況又是不同的。

    研究人員本杰明·沃埃特說：“這項研究讓我們思考一個問題：人類還在進化嗎？答案是：絕對在進化。”

    這項新研究讓我們聯(lián)想到人類歷史上發(fā)生的重大事件。

    主研究員、芝加哥大學的人類遺傳學專家喬納森·皮查德說：“人類最近有很多進化現(xiàn)象：在過去一萬年中，農(nóng)業(yè)、飲食、棲息地、和氣候都有很大變化。”

    研究人員還首次發(fā)現(xiàn)四種色素基因的進化對歐洲人至關(guān)重要。科學家認為歐洲人的膚色很淺的原因正是為了避免吸入過多的陽光。

    科學家在中東人體內(nèi)的乙醇脫氫酶中也發(fā)現(xiàn)了積極選擇的證據(jù)。這種酶能夠快速瓦解酒精。很多中東人都有基因突變現(xiàn)象，導(dǎo)致不能產(chǎn)生乙醇脫氫酶。科學家相信這種突變也一定是為了適應(yīng)某種環(huán)境而發(fā)生的。

    此項研究根據(jù)國際人類基因組單體型圖計劃提供的數(shù)據(jù)撰寫而成，刊登在3月7日的生物科學公共圖書館雜志中。