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【科普】太平洋上的人群定居
Local languages and stomach bacteria both tell the story of how people migrated out of Asia and spread across the Pacific, scientists say in two complementary studies in the January 23 issue of Science.
Researchers have long been interested in how humans populated the Pacific, including its many far-flung, isolated islands, Colin Renfrew explains in a Perspective that discusses both articles. Taking a new approach to the problem, Yoshan Moodley and colleagues sampled Helicobacter pylori bacteria from aboriginals in Taiwan and Australia, highlanders in New Guinea, and Melanesians and Polynesians in New Caledonia. H. pylori occurs in the stomachs of about half the population that does not have access to modern medicines. Because it is so specific to humans it has spread around the world and diverged genetically alongside its host. Moodley and colleagues compared the DNA sequences of their bacterial samples and identified two strains that appear to have been evolving separately for thousands of years. One, which they call hpSahul, split from Asian populations of H. pylori more than 30,000 years ago, probably as people migrated across the exposed land bridges of what is now the Indonesian Archipelago, into New Guinea and Australia. The other strain, hpMaori, dispersed from Taiwan about 5,000 years ago, as a second wave of people migrated to the Philippines and into Polynesia and New Zealand.
R.D. Gray and colleagues analyze this second migration in more detail in their comparison of Austronesian languages. They constructed an evolutionary tree showing the relationships among 400 languages, based on similarities, or “cognates” across a set of 210 core vocabulary words. The results indicate that the Austronesian language family has a root in Taiwan and began diversifying about 5,000 years ago. The migration also included two major pauses, the first between settlement of Taiwan and the Philippines, possibly due to the difficulties in crossing the 350-kilometer channel separating the two, and the second in Western Polynesia, perhaps because further technological and/or social innovations were necessary for dealing with the vast distances between islands in Eastern Polynesia.
科学家们在２篇互为参证的研究中说，地区性的语言和胃里的细菌都告诉了我们人类是如何从亚洲迁徙出来并在整个太平洋中散布开来的。
研究人员长期以来都对人群是如何在太平洋上各地区定居的感到兴趣，包括人们是如何在许多地处偏远且与外界隔离的岛屿上定居的。Colin Renfrew在一篇讨论这２篇文章的Perspective中，对这一问题进行了解释。Yoshan Moodley及其同僚对这一问题采用了一种新的研究方法，他们对台湾和澳大利亚的土著人、新几内亚高地人以及居住在新喀里多尼亚的美拉尼西亚和波利尼西亚人体内的幽门弯曲菌（Helicobacter pylori）进行了采样。在那些无法获取现代医药的人群中，大约有一半的人的胃中有幽门弯曲菌。由于这种细菌是人特有的，因此它随着其宿主在世界上传播，而且随着宿主而发生遗传上的歧化。Moodley及其同僚对他们的细菌样本的DNA序列进行了比较并发现了2个菌株，这两个菌株看来已经分别演化达数千年之久。其中一个菌株（他们称为hpSahul）在3万年前就与亚洲人的幽门弯曲菌分道扬镳，这可能与人们跨越暴露的大陆桥（即现在的印度尼西亚群岛）进入新几内亚和澳大利亚有关。另外一个菌株（hpMaori）是在大约5000年前从台湾播散出去的，当时第二波的人潮迁徙到了菲律宾并进入波利尼西亚和新西兰。
R.D. Gray及其同僚在他们对南岛语言的比较中对这一第二波的迁徙进行了更为详尽的分析。他们基于跨越一整套内有210个核心词汇的字的语言的相似性（或称“同源性”）构建了一颗演化树，从中显示了400种语言之间的关系。结果表明，南岛语系植根于台湾，并在大约5000年前开始多元化。人口的迁徙也包括2次主要的停顿，第一次停顿发生在人们定居在台湾和定居在菲律宾的时期之间（造成这一停顿的原因可能是人们在跨越隔开两者的长达350英里的海峡时遭遇困难）；第二次的停顿发生在西波利尼西亚（造成这一停顿的原因或许是人们在应付与东波利尼西亚的岛屿之间的辽阔的距离时必须要有更进一步的技术和/或社会的创新）。 [标签:content1][标签:content2]
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作者:admin@医学,生命科学 2011-04-16 05:11
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