8,000 Years Ago, 17 Women Reproduced for Every One Man
八千年前，17名女性为1名男性传宗接代
【编者按：原谅我不得不写一段长长的按语。本文所报道的研究非常有意思，但报道本身写得很差。这项研究所揭示的其实是这样一个事实：从大约一万年前开始，也就是农业诞生后不久，人类男性中留下后代的比例经历了一次急剧下降，这段下降期为时约四千年，接着又迅速回升。对此，研究者作出的猜测是：在此期间男性的性竞争强度剧增，原因可能是财富和权势积累并集中在少数人手里。所面临的性选择压力。当然，男性之间的性竞争强度历来很高，而且远远高于女性，对比两幅图可以看出，在历史上大部分时间，留下后代的男性数量大概只有女性的1/4，但农业起源后，这一比例突然跌到1/17，这是极不寻常的。】
An analysis of modern DNA uncovers a rough dating scene after the advent of agriculture.
一项对现代DNA的分析揭示了农业出现以后人类两性关系的大致图景。
Threshing wheat in ancient Egypt. 古埃及的打麦场面（Photo: Carlos E. Solivérez/Wikimedia Commons）
Once upon a time, 4,000 to 8,000 years after humanity invented agriculture, something very strange happened to human reproduction. Across the globe, for every 17 women who were reproducing, passing on genes that are still around today—only one man did the same.
很久以前，在农业诞生之后4000到8000年间，人类繁衍活动中发生了一些非常奇怪的事情。全世界每17名女性进行生育繁衍、从而得以将其基因留传至今的同时，却仅1名男性有这样的机会。
“It wasn’t like there was a mass death of males. They were there, so what were they doing?” asks Melissa Wilson Sayres, a computational biologist at Arizona State University, and a member of a group of scientists who uncovered this moment in prehistory by analyzing modern genes.
“看来并不像是男性经历了大规模死亡，他们都安然地活着。可既然如此，他们到底怎么啦？”Melissa Wilson Sayres问道，她来自亚利桑那州立大学的一位计算生物学家，包括她在内的一群科学家，正试图通过分析现代基因来解密这一史前现象。
Another member of the research team, a biological anthropologist, hypothesizes that somehow, only a few men accumulated lots of wealth and power, leaving nothing for others. These men could then pass their wealth on to their sons, perpetuating this pattern of elitist reproductive success.
该研究团队的另一名成员，一位生物人类学家，提出了这样一个假设：只有少数男性能够积累大量财富与权势，而其他男性则一无所有。这些有钱有势的男性将他们的财富传给自己的子孙，以保持世世代代精英繁衍的模式。
Then, as more thousands of years passed, the numbers of men reproducing, compared to women, rose again. “Maybe more and more people started being successful,” Wilson Sayres says. In more recent history, as a global average, about four or five women reproduced for every one man.
如此过了几千年之后，有繁殖机会的男性的比例（相对于女性）再次升高。“也许是成功男士越来越多了。”Wilson Sayres说。在较晚近的历史时期，全球范围内平均4到5名女性为1名男性传宗接代。
These two graphs show the number of men (left) and women (right) who reproduced throughout human history. (Chart: Monika Karmin et al./Genome Research)
这两幅图展示了人类历史上进行了生育的男性数量（左）与女性数量（右）
Physically driven natural selection shaped many human traits.Ethnic Africans and Europeans had to evolve to digest milk, for example, while most ethnic Tibetans have adaptations to deal with the lower oxygen levels at high altitudes. But if Wilson Sayres’ team’s hypothesis is correct, it would be one of the first instances that scientists have found of culture affecting human evolution.
针对生理方面的自然选择塑造了人类的种种特性。例如（民族意义上的）非洲人和欧洲人进化得能够消化牛奶，而多数西藏人则拥有了对付高海拔地区稀薄氧气的适应器。可是假如Wilson Sayres团队提出的假说是正确的，这将是科学家找到的第一批人类文化影响自身进化的例证之一。
The team uncovered this dip-and-rise in the male-to-female reproductive ratio by looking at DNA from more than 450 volunteers from seven world regions. Geneticists analyzed two parts of the DNA, Y-chromosome DNA and mitochondrial DNA. These don’t make up a large portion of a person’s genetics, but they’re special because people inherit Y-chromosome DNA exclusively from their male ancestors and mitochondrial DNA exclusively from their female ancestors.
研究团队观察分析了来自全球7个地区450多名志愿者的DNA后，发现男女生育比例的这一大起大落。遗传学家分析了DNA的两个部分——Y染色体DNA和线粒体DNA。它们只占个体遗传物质的一小部分，但其特殊之处在于，Y染色体DNA只能继承自父系祖先，而线粒体DNA只能继承自母系祖先。
By analyzing diversity in these parts, scientists are able to deduce the numbers of female and male ancestors a population has. It’s always more female.
通过分析不同个体间Y染色体DNA和线粒体DNA的多样化程度，科学家得以此推测一个种群中男性祖先和女性祖先的数量。女性祖先总是多于男性祖先。
So much for what our DNA can tell us. This study, published last week in the journal Genome Research, can’t directly account for why the dip occurred. Instead, the team members tried to think through other explanations. “Like was there some sort of weird virus that only affected males across the whole globe, 8,000 years ago?” Wilson Sayres asks—a hypothesis the team found unlikely.
我们的DNA能告诉我们的就这么多了。上周在 Genome Research 期刊上发表的这项研究，并不能直截了当的解释上述大起大落的原因。研究团队也在努力寻找其他可能的解释。“比如说8000年前全球爆发了一种只感染男性的奇怪病毒？”Wilson Sayres说道——但这个假设大家都觉得不太可能。
To further test the wealth-and-power idea, the researchers plan to look for other genetic markers that would indicate that something cultural, not physical, kept those early male farmers from reproducing. Team members could also collaborate with anthropologists and archaeologists, to see if they have any clues.
为了进一步验证“财富与权势”假说，研究者们计划寻找适当的遗传标记，能够揭示某些妨碍早期男性农耕者生育繁衍的文化而非生理因素。他们也希望与人类学家和考古学家开展合作，看看他们能否提供什么线索。
Nature is a harsh taskmaster, but so, it seems, is human culture. Although the popular notion is that farming and settlement cushioned people against “survival of the fittest,” this study shows that’s not true. Something cultural happened 8,000 years ago that’s marked us even today.
大自然是个严酷的工头，但现在看来，人类文化似乎也是。尽管流行观点认为，农耕与定居已将人类从“最适者生存”的法则中解放，但这项研究却告诉我们真相并非如此，8000年前的某些文化条件留在我们身上的印迹至今仍在。
翻译：Eartha（@王小贰_Eartha)
校对：陆嘉宾（@晚上不买白天买不到）
编辑：辉格@whigzhou