Modern humans left Africa just once, scientists say

<body leftmargin="0" bgcolor="#000060" text="#FFFFFF" link="#FFFF00" vlink="#FF9900"> <b> <p class="MsoNormal"><font face="Arial" size="5">Modern humans left Africa just once, scientists say</font></p> </b> <p class="MsoNormal"><font face="Arial" size="1">Posted May 13, 2005<br> Courtesy Science<br> and World Science Staff<br> </font> <b> <font size="2" face="Arial"><br> The first modern humans to leave East Africa and populate Asia may have traveled along a coastal route rather than through the Middle East, as the traditional view among scientists holds, according to a pair of genetic studies.  </font></b> </p> <p class="MsoNormal"><b><font face="Arial" size="2"> One of the two studies also concludes that this dispersal was a single, rapid event that could have led to the subsequent peopling of Europe and Asia.</font></b> </p> <p class="MsoNormal"><b><font face="Arial" size="2">The studies are published in today’s issue of the research journal <i>Science.</i></font></b> </p> <p class="MsoNormal"><b><font face="Arial" size="2"> Much of what we know about human migrations comes from studying mitochondrial DNA, which is inherited maternally, from modern populations. </font></b> </p> <p class="MsoNormal"><b><font face="Arial" size="2"> The amount of variation among different groups’ mitochondrial DNA sequences generally reflects the amount of time since the groups diverged from each other. Kumarasamy Thangaraj and colleagues used this approach to study indigenous tribal populations on the Andaman and Nicobar Islands, which lie between India and Myanmar. </font></b> </p> <p class="MsoNormal"><b><font face="Arial" size="2"> They identified two relatively old populations of Andaman Islanders that probably survived in genetic isolation there since the out-of-Africa migration. In contrast, the Nicobarese populations appear to be closely related to other populations in Southeast Asia, suggesting that their ancestors arrived much more recently from the east.</font></b> </p> <p class="MsoNormal"><b><font face="Arial" size="2"> The mitochondrial DNA of the aboriginal Orang Asli of Malaysia also supports the idea that humans leaving Africa dispersed along a southern coastal route through India and into southeast Asia and what is now Australia, according to a second study. </font></b> </p> <p class="MsoNormal"><b><font face="Arial" size="2"> The Orang Asli likely branched off from other Asian lineages around 60,000 years ago, soon after their ancestors left Africa. Vincent Macaulay and his international research team propose that there was an early offshoot, leading to the settlement of the Near East and Europe, but that the main dispersal from India to Australia was extremely rapid, taking only a few thousand years. A related commentary in the journal notes that populations such as the Andamanese and the Orang Asli are dwindling, so time is short for gathering data about them.<br> </font></b> </p> </body>