和尚图片头像帅气:人类的进化由寄生虫驱使？

寄生虫催使人类进化？

Humans live in all sorts of places—high deserts, tropical lowlands, frigid tundra. Over the millennia, you’d expect each population’s assortment of genes to evolve to reflect the demands and dangers of its home environment: those who live in the deserts would possess genes for extra skin pigments to help keep their tender integument from burning (like African peoples), and those who live in sub-zero climes much of the year would have genes that keep them well-insulated in fat (like the Inuit). But what if factors other than climate, like the food available nearby or the viruses, bacteria, and parasites native to the area, also had an effect on various human populations’ genetic toolkits?

无论高原上的沙漠，热带低地还是寒冷的苔原，到处都有人类生活的痕迹。几千年以来各个物种基因的进化历程反映了存在其生活环境中的危险及与之相关的需求：生活在沙漠中的人们的基因含有较多皮肤色素以防止脆弱的包膜被晒伤（非洲人就是个很好的例子），而那些常年生活在零下气候中的其基因则帮助他们保持绝缘性能良好的脂肪（像因纽特人那样）。但是如果除开气候这一因素，像就近的食物资源或者作为原住民的病毒，细菌和寄生虫等也能对丰富的人类基因工具箱产生影响呢？

It’s a fascinating question, but, given that we have to reconstruct all this supposed evolution from the current state of modern genomes, finding an answer isn’t easy. A recent paper takes an important first step by looking for correlations between 500,000 different genetic markers and certain environmental characteristics, like humidity, temperature, the local diet, and the prevalence of parasites and other pathogens. The researchers started out with the genetic information (specifically, their  single nucleotide polymorphisms, or SNPs, small differences in the genetic code) of 1,500 people hailing from 55 different populations, including two groups of  Bantus,  Uygur, and  French Basque, and a list of environmental measurements (you can check out their starting data in the three Excel tables here)

这是个很迷人的问题，鉴于我们必须从现代基因组来重建所有假设的进化演变，找出答案十分不易。近期的一篇论文在这一方面迈出了重大的一步，其试图从500,000种不同的基因标记与包括湿度，温度，当地饮食，盛行的寄生虫与其他的病菌等环境因素之间找出他们的关联。研究人员从1500个包括班图，维吾尔族，巴斯克等不同人种的基因（特别是单核苷酸多态性，简称SNPs，即基因密码的微小差异），以及一个环境测量的目录开始。 

Most of the genetic variation between populations turned out be to attributable to drift (the gradual differences that build up between populations that don’t interbreed much), but they did find that some noticeable differences were related to pathogens, food, and climate, with pathogens, parasites especially, having the lion’s share. This suggests that parasites could have driven human evolution, the researchers write, and they opine that this might be because parasites like helminth worms have relatively long life-cycles, so humans had a chance to evolve adaptations to combat them, while short-lived bacteria and viruses might not be causing such strong effects. There are still plenty of gray areas in this realm of  population genetics, as outside experts interviewed by Nature News point out: it’s likely that climate, food, and pathogens are closely intertwined as sources of human evolutionary pressure (and furthermore, this study found correlations—not causation). But this paper is an interesting step forward in exploring what forced us to evolve.

这是个迷人的问题，鉴于我们必须从现代基因组来重建所有假设的进化演变，要想找出答案十分不易。近期的一篇论文在这一方面迈出了重大的一步，其试图从500.000种不同的基因标记与包括湿度，温度，当地饮食，盛行的寄生虫与其他病菌等环境因素之间找出它们的关联。研究人员从1500个包括班图，维吾尔族，巴斯克等不同人种的基因（特别是单核苷酸多态性，简称SNPs，即基因密码的微小差异），以及一个环境测量的目录开始。

大部分人种间的基因差异缘起漂移（在无需过多异种交配的人种间建立起来的渐进的差异）。研究人员同时发现一些明显的差异与病毒，食物，气候尤其是病毒，寄生虫相关联。后者占据大部份额。这意味着寄生虫可能驱动了人类的进化，研究人员写到。并且认为也许是因为蠕虫之类的寄生虫拥有较长的生命周期，因此人类才借机进化与之对抗，而寿命较短的细菌和病毒则无法起到如此强大的效果。在人类基因的领域里始终存在大片模棱两可的区域，正如被自然新闻采访的外行专家所指出的那样：极有可能气候，食物，病毒等因素紧密缠绕一起作为人类进化的压力（更深层次上，该研究发现了一些关联——非因果联系）。在到底是什么迫使我们进化的探索中此篇论文迈出了有趣的一步。