解释基因多样性锐减的最佳答案：古代氏族间的战争

　　Men inherit their Y chromosomes from their fathers. And they get an almost exact copy, other than a few mutations. Meaning very little changes about the Y chromosome from generation to generation.

　　人类从他们的父辈那里继承Y染色体。除了些许突变，他们几乎是一个复制体。也就是说，代代相传，而Y染色体只改变一点点而已。

　　"You may just have 100 people with the same Y chromosome, because they’re all descended from one man." Marcus Feldman, a population geneticist at Stanford. "They all had this great great-great-great-great-great-great-grandfather. And every male relative of that individual who’s a first-degree relative has the same Y chromosome."

　　“一百个人由于都继承于一个男性个体，因此他们也许有同样的Y染色体。” 斯坦福的人类基因学家，马库斯.费尔德曼说，“他们都有这位爷爷的爷爷的爷爷的爷爷的爷爷的爷爷的爷爷的爷爷的Y染色体。第一代亲戚的每个男性个体的亲戚都有着同样的Y染色体。”

　　Researchers have thus used Y chromosome data—along with mitochondrial DNA, which is passed down only by our mothers—to investigate aspects of ancient populations. For example, one recent study found a huge drop in Y chromosome diversity five-to-seven thousand years ago. At the same time, mitochondrial DNA diversity continued to grow, implying a possible crash in the male population, with 17 women to every man. But:

　　研究者有了这样的Y染色体资料-再加上从母体继承的线粒体DNA，就可以调查研究古代人口的各个方面情况。例如，最近一项研究发现5到7千年前Y染色体急剧减少。同时，线粒体多样性在不断上升，这个现象暗示了男性数量可能出现了塌方式锐减，男女比例呈现1:17。但：

　　"It seemed to us that the 17-to-1 sex ratio was just too extreme to be real."

　　“1:17的性别比例看起来有点不可思议，甚至于不真实。”

　　So Feldman and his team used computational models to investigate other ideas. And they found that bloody fights between genetically homogenous clans could have produced the same results. "Essentially we’re saying the clans fighting one another are built around having the same Y chromosome."

　　因此，费尔德曼和他的团队利用电脑模型对他们的猜想进行了研究调查。他们发现基因同族之间的骨肉相残可能产生了这样的结果。“从根本上来讲，有着着同样的Y染色体的氏族之间发生了争斗。”

　　Imagine a single deadly battle knocking out a whole clan of men with the same Y chromosomes. Then repeat that unpleasant scenario a few times. You’d get a huge drop in the diversity of Y chromosomes, as the victorious clans won battles and expanded. The details are in the journal Nature Communications.

　　想象一下，有这样一场致命的争斗，它造成了继承有同样的Y染色体全部消失。然后同样令人堪忧的剧情上演了多次。那么，由于胜利的族群赢得了战斗并且迅速扩张，Y染色体的多样性就会出现急剧减少。详细信息刊登在了NATURE COMMUNICATIONS。

　　Eventually, Y chromosome diversity bounced back, as smaller clan structures were replaced by large, genetically diverse cities and societies—a cultural innovation that we, too, inherited.

　　最终，由于更小的族群结构由庞大，基因多样的城市和社会群体替代，Y染色体的多样性就出现了反弹—我们也继承了这样的文化革新。