Blogs / 80beats

The small band of Homo sapiens that left Africa around 60,000 years ago, taking the first steps on a journey that would eventually disperse humans all around the world, may have been composed mostly of men. A new analysis of DNA variations in contemporary humans indicates that non-Africans descend from a population that contained far more males than females [New Scientist].

In the study, published in Nature Genetics [subscription required], researchers compared genetic samples from present-day African, European, and Asian populations. They were looking at the chromosomes that determine sex (two X chromosomes in women, one X and one Y chromosome in men), as well as the other 22 chromosome pairs, which are the same in both sexes. They examined the rate at which mutations randomly spread through the X chromosome over dozens or hundreds of generations as compared to the mutation rate in other, non-sex, chromosomes [AFP].

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The tumult of the Spanish Inquisition, which began over 500 years ago, has echoed down through the generations of people living on the Iberian peninsula in a remarkable way. A new genetic study has revealed that many current Spaniards have Sephardic Jewish or North African heritage, indicating that their ancestors converted to Christianity during the religious upheaval of the 15th century in order to remain in Spain. The study showed that one in ten Iberians has a North African ancestor, while one in five had Jewish forebears.

This melting pot probably occurred after centuries of coexistence and tolerance among Muslims, Jews and Christians ended in 1492, when Catholic monarchs converted or expelled the Islamic population, called Moriscos. Sephardic Jews, whose Iberian roots extend to the first century AD, received much the same treatment. “They were given a choice: convert, go, or die,” says Mark Jobling, a geneticist at the University of Leicester, UK. Some of those that became Christian would have ended up contributing genes to the Iberian pool [New Scientist].

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The newly elected president of the Maldives, the island chain south of India, says his country must start saving up money to buy a new homeland, in case global warming causes sea levels to rise so much that the waves submerge the archipelago entirely. Says Maldivian President Mohamed Nasheed: “We can do nothing to stop climate change on our own and so we have to buy land elsewhere. It’s an insurance policy for the worst possible outcome…. We do not want to leave the Maldives, but we also do not want to be climate refugees living in tents for decades,” he said [The Guardian].

The Maldives are the lowest-lying nation on the planet: most of the islands are only a few feet above sea level, and the highest point, in the capital city of Malé, is about seven feet above sea level. But the white sandy beaches are a major tourist attraction bringing in billions of dollars every year…. Mr Nasheed’s plan is to create a “sovereign wealth fund” using tourism revenues to buy land so that future generations will have somewhere to rebuild their lives if they have to leave. He wants somewhere within the region, where the culture is similar - possibly India or Sri Lanka [BBC News]. However, Nasheed also mentioned Australia as a possibility, because of the vast swaths of unoccupied land on that continent.

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Researchers have long debated whether human migration out of Africa was spurred by climate changes that forced the early humans to move along or by technological innovation that let them take advantage of new possibilities; now a new analysis of stone tools from southern Africa is lending support to the latter camp. Researchers determined that two types of tools were developed during the crucial age from 60,000 to 80,000 years ago when modern humans began to move towards new regions of the globe.

Researchers examined tools from nine sites in South Africa, Namibia, and Lesotho. The sophisticated Still Bay tools were made from hard, fine-grained rock called silcrete, and were fashioned between 71,000 and 71,900 years ago. The Howieson’s Poort implements were made between 59,500 and 64,800 years ago, and were composed of chipped silcrete rock attached to wood shafts to form weapons. Comparing these dates with palaeoenvironmental records failed to turn up a close correlation between the industries and dramatic climatic changes, [lead researcher Zenobia] Jacobs says. “We see no consistent pattern between the timing of these industries and major climatic changes” [Nature News].

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The first migration of Homo sapiens, when they left the East African landscapes where they evolved and began a long trek across the Sahara, may have followed a different route than previously believed. A new study shows that prehistoric river channels fed by monsoons once traced a path north through the desert and argues that the modern humans may have followed those channels, going from oasis to oasis until they reached the sea.

The Sahara has had several periods of increased rainfall that made it a wetter and greener place, including one interlude between 130,000 to 170,000 years ago when the researchers believe these river channels flowed with water. Now only visible with satellite radar, the channels flowed intermittently from present-day Libya and Chad to the Mediterranean Sea, says [lead researcher] Anne Osborne…. Up to five kilometres wide, the channels would have provided a lush route from East Africa – where modern humans first evolved – to the Middle East, a likely second stop on Homo sapiens‘ world tour [New Scientist].

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When the Vikings set sail for the British Isles they had small, furry stowaways aboard their ships, and researchers say that the descendants of those mice can offer clues about the voyages taken by Viking seafarers. A new study examined the DNA of house mice throughout the British Isles and found that mice from areas where the Vikings are thought to have settled are genetically distinct from mice in other regions.

Says study coauthor Cath Jones: “We have found that most of the mice in the north of Scotland – from Orkney, Shetland and Caithness – are all of one very similar type that we have named the Orkney lineage and they are very similar to Norwegian mice. And the only explanation for that is that when the Vikings came raping and pillaging to Scotland they took their house mice with them” [Scotsman].

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By examining half a million tiny differences in the genomes of Europeans, researchers can determine with surprising accuracy where on the continent each person comes from, easily distinguishing the Irish from the English, for example. Two new studies reveal that our DNA contains a sort of global positioning system, which researchers can use to pinpoint where in the world both we and our relatives came from [ScienceNOW Daily News].

The findings surprised geneticists by showing that despite centuries of immigration and intermarriage throughout Europe, genetic differences between Europeans are almost entirely related to where they were born. This, however, does not mean that the citizens of each European nation represent miniature races. “The genetic diversity in Europe is very low. There isn’t really much,” says Manfred Kayser [New Scientist], author of one of the studies.

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A clump of hair that lay frozen in the Greenland tundra for 4,000 years has yielded DNA from the earliest Arctic residents, and offers clues to their origins.

Researchers have long wondered who those rugged settlers were, and where they came from. Were they part of a massive migration that swept through all of North America, or were they a separate tribe that eventually gave rise to Greenland’s present-day Eskimos?

Until now, no ancient human remains had been found in that harsh climate to allow researchers to study the genetics of those “Paleo-Eskimos.” But the new discovery sheds some light on the people, and suggests that neither of the earlier theories is correct; in fact, they were a distinct tribe that journeyed all the way from Siberia to Greenland, but didn’t stick around to populate the frozen north.

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