博主胡德良：邢台学院外语系英语教授,中国译协专家会员,河北省译协常务理事,邢台市译协副会长。爱好翻译,内容涉及宇宙探秘、医疗卫生、家庭保健、生命科学、能源科学、地球科学、环境科学、散文小说和纪实文学等领域。所译文章曾见于《光明日报》《科技日报》《健康时报》《健康报》《英语世界》《英语知识》《科技英语学习》《科学之友》《科学与文化》《世界科学》《生命世界》等全国各大报刊。博客特色：英汉对照、图文并茂,融趣味性、科学性、知识性为一体。
一项研究表明，人们是多次分批达到南北美洲的。
Tracing Humanity's Path
By Michael Balter 胡德良 译
| Most researchers agree that modern humans got their start in Africa and then spread throughout the world beginning about 50,000 years ago. But scientists are still working out the details of how the planet was peopled, such as who went where, and when. A new study, employing sophisticated modeling techniques, confirms the prevailing Out of Africa model but also comes up with some surprises, including evidence that the Americas' first human inhabitants arrived in multiple waves. | 多数研究人员同意这个观点：现代人类起源于非洲，后来在大约5万年前开始向世界各地流散。但是，科学家们仍然在研究人类曾经在地球上分布的详细情况，如：何人迁移到何地，又是在何时进行迁移的，等等。一项新研究利用尖端的模拟技术，不但证实了“源自非洲”的流行理论模型，而且还发现了一些令人吃惊的情况，其中包括有证据显示最初的美洲居民是多次分批迁移而至的。 |
| Archaeologists and anthropologists worldwide have dug up plenty of skeletons over the years, but the bones seldom say much about where ancient peoples originally came from. Thus researchers have tried using variations in the genes of living individuals to trace their ancestries back to prehistoric times. In general, the closer two modern populations are genetically, the more likely that they share a common ancestry; yet this ancestral heritage is sometimes obscured by genetic changes that have taken place over thousands of years, as well as by interbreeding between populations. Happily, efforts to get around these complications have been boosted by an ever-growing mound of data about genetic differences between human populations. | 多年来，全世界的考古学家和人类学家挖出了大量的人类骨架，但这些骨架很难充分说明古代人类最初源于何地的问题。这样，研究人员尝试利用活人基因的变异情况追溯到史前的年代，以探索其祖先的来源。一般说来，两个现代人类种群在基因上越接近，他们拥有共同祖先的可能性就越大。然而，由于不同种群之间的杂交繁殖以及几千年来所发生的基因变化，祖先的遗传特点有时会变得模糊不清。令人欣慰的是，有关人类种群之间基因差异的数据资料不断得到丰富，有助于摆脱上述的复杂因素。 |
| A team led by geneticist Daniel Falush of University College Cork in Ireland developed a new mathematical model to compare not just individual genes or short DNA segments, as previous studies have done, but also very long stretches of DNA. Falush and his colleagues analyzed 32 DNA segments, each consisting of more than 300,000 base pairs, from 927 people representing 53 different populations from around the globe. Plugging this huge amount of data into computer simulations, the team worked out which migration scenarios were most likely to have created the genetic variation we see today. The results, reported today in PloS Genetics, suggest that modern humans peopled the world in nine phases, beginning in Africa, moving on to Europe and Asia, and finally colonizing the Americas and the Pacific islands. (The team illustrates humanity's journey in two movies accompanying the paper; see below.) The team did not try to date the migrations. | 爱尔兰科克大学的遗传学家丹尼尔·法拉士领导着一个研究小组，开发了一种新型数学模拟法，不但可以象以前的研究所做的那样——对比个人基因或短链DNA片段，而且还可以比较特长链DNA。法拉士及同事分析了32个DNA片段，每个片段包括30多万碱基对，采样于729人，他们来自全世界各地，代表着53个不同的人类种群。把这些大量的数据资料输入计算机进行模拟时，研究小组经计算得知哪些迁移设想最可能产生我们今天看到的基因变异情况。研究结果报道在今天出版的《科学公共图书馆-遗传学》上。该研究结果表明：现代人类在世界上的定居分九个阶段，最初在非洲，后来迁移到欧洲和亚洲，最后在美洲及太平洋诸岛开辟了殖民地。研究小组没有努力考证迁移的具体时间。 |
| The study came up with two unexpected findings. One is that the people of the Orkney Islands, to the north of Scotland, share some ancestry with Siberians, possibly because some ancestors of modern Orcadians ventured to Asia via the Arctic Circle. The team also found that North and South America were colonized independently by at least two different waves of migration from different parts of Asia, although both waves appear to have arrived via the Bering Strait. This conclusion contradicts the conventional view, which postulates just one migratory wave out of Asia. | 该研究获得了两个出人意料的发现。一个发现是，苏格兰以北奥克尼群岛上的某些人们的祖先同样也是西伯利亚人的祖先，可能是由于现代奥克尼人的一些祖先曾经冒险途径北极圈迁移到亚洲的缘故。研究小组还发现，至少有前后两批来自亚洲不同地区的移民分别在南北美洲开辟了殖民地，两批移民好像都是经过白令海峡到达美洲的。这个结论与传统的观点相矛盾，据传统的观点推测，只有一批移民来自亚洲。 |
| "I like the paper very much," says Jonathan Pritchard, a human geneticist at the University of Chicago in Illinois. "It's a very novel and creative way of thinking about the data" that "may provide a better representation of human history." Ripan Malhi, a molecular anthropologist at the University of Illinois, Urbana-Champaign, says that the team's approach "holds great potential to give us important and novel insights into the peopling of the Americas." Nevertheless, Malhi cautions that the multiple migrations Falush and his colleagues detect in the Americas might be an artifact of ancient population movements "more complex than the simple models created in this study can accommodate." | “我很喜欢这篇论文，”伊利诺斯州芝加哥大学的人类遗传学家乔纳森·普里查德说，“它利用非常新颖而富有创建性的方法分析了数据，这些数据可能会更加清晰地展现人类历史。”伊利诺斯大学厄本那-香槟分校的分子人类学家里潘·马里指出，研究小组的研究方法“极有可能使我们对美洲人的定居情况产生重大而全新的了解”。然而马里警告说，法拉士及同事在美洲发现的多次移民活动可能是古代人口走动的产物，“这个问题更加复杂，并非该研究创设的简单模拟所能解决的。” |
译自：美国《科学》杂志网（23 May 2008）
月亮飞船经典日志导读
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