Genetic 「Eve，」 「Adam」 lived roughly at same time： study
The most recent common ancestors to females and males， 「Eve」 and 「Adam，」 appeared on the planet roughly around the same time， U.S. researchers said Thursday.
A study led by the Stanford University School of Medicine， which appeared in the journal Science， determined that our male most recent common ancestor (MRCA) known as Y-chromosomal 「Adam」 lived 120，000 and 156，000 years ago， overlapping with Mitochondrial 「Eve」 who lived 99，000 and 148，000 years ago.
Initial estimates for the male MRCA ranged from between 50，000 to 115，000 years ago.
The researchers compared the sequences of Y-chromosome， which is passed only from father to son， among 69 men from nine globally distinct regions， including some that have only recently been available for study. Regions represented included Namibia， the Democratic Republic of Congo， Gabon， Algeria， Pakistan， Cambodia， Siberia and Mexico.
The researchers identified about 11，000 differences among the sequences， which enabled them to establish phylogenetic relationships and timelines among the sequences 「with unprecedented accuracy.」
They found that the most recent male common ancestor with a Y- chromosome appeared on the planet between 120，000 to 156，000 years ago.
By applying the same analytical techniques to mitochondrial DNA， which was passed only from mother to daughter， the researchers also calculated that mitochondria and the modern maternal lineage originated sometime between 99，000 and 148，000 years ago.
「Previous research has indicated that the male MRCA lived much more recently than the female MRCA，」 said Carlos Bustamante， professor of genetics at the Stanford University and senior author of the study. 「But now our research shows that there『s no discrepancy.」
Despite the 「Adam」 and 「Eve」 monikers， which evoke a single couple whose children peopled the world， it is 「extremely unlikely 「 that the male and female MRCAs were exact contemporaries， the researchers said.
They weren’t the only man and woman alive at the time， or the only people to have present-day descendants， the researchers said.
These two individuals simply had the good fortune of successfully passing on a portion of their genomes to the vast expanse of humanity， through the millennia to most of us， while the corresponding sequences of others have largely died out due to natural selection or a random process called genetic drift， according to the study.
相關新聞：常理上男人和女人相伴而生，傳說中亞當和夏娃孕育了人類。但實際上我們現代人類並不是由我們的共同男性祖先和女性祖先一起孕育的，「亞當」與「夏娃」可能大致生活年代相同，但並未生活在一起。這聽起來像繞口令，且看美國研究人員在《科學》雜誌上是怎麼報告的。
人類男女祖先「年齡」的秘密隱藏在Ｙ染色體與線粒體中。Ｙ染色體只從父傳子，而線粒體只從母傳女。通過這兩種遺傳物質向前追溯，可以發現所有男人都有共同的男性祖先「Ｙ染色體亞當」，所有女人都有共同的女性祖先「線粒體夏娃」。
此前研究認為，這個男性共同祖先「亞當」生活在１１．５萬到５萬年前，而這個女性共同祖先「夏娃」則生活在更早的２４萬到１５萬年前。此次美國史丹福大學的研究負責人波茲尼克說，「我們的研究顯示，這種（時間）差異並不存在。事實上，『Ｙ染色體亞當』或許（年齡）還大一點。」
研究人員對來自亞非拉等代表９個不同人群的６９名男性進行基因組測序並比較分析，結果發現，這些男性的Ｙ染色體序列中存在約１．１萬個突變，這些突變使得他們以「前所未有的準確率」構建了Ｙ染色體譜系樹，研究人類Ｙ染色體的遺傳進化。
研究人員據此得出結論認為，這個男性共同祖先「亞當」於１５．６萬年至１２萬年前生活在地球上。對線粒體採用同樣的分析技術，研究人員又推算出這個女性共同祖先「夏娃」生活在１４．８萬年至９．９萬年前。這兩個時間段存在較大重疊，據此判斷，這兩位差不多生活在同一時期，「年齡」比較接近，這個「亞當」可能還要稍早點。
研究人員指出，這裡所說的「亞當」與「夏娃」並不是說當時地球上只有他一個男人或只有她一個女人，他們只是在當時的古人類群體中幸運地將Ｙ染色體與線粒體遺傳至今的兩個個體。作為兩個個體，「亞當」與「夏娃」應該從未相遇。
（實習編輯：於曉偉）