Random Samples

Science  28 Jul 2006:
Vol. 313, Issue 5786, pp. 419

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    Anglo-Saxon helmet, from 7th century east Anglia.CREDIT: THE TRUSTEES OF THE BRITISH MUSEUM

    The Anglo-Saxons who invaded Britain from northern Germany in the early 5th century C.E. and ruled over England for 600 years left a huge genetic imprint. Y chromosome studies show that they contributed up to 72% of the modern English gene pool.

    How did they do it? Native Britons numbered about 2 million in the 5th century, so to sweep the gene pool, the Anglo-Saxons would have had to number about 500,000—far more than suggested by archaeological and historical evidence.

    Instead, the Anglo-Saxons leveraged their DNA by ruling as an elite and separate group whose favored status allowed them to have more offspring than the Britons, claims a team led by geneticist Mark Thomas of University College London. The team used computer simulations that varied the number of invaders, the rate of intermarriage, and the postulated reproductive advantage. For example, even if the invaders were only 5% of the population, their Y chromosomes would reach the 50% mark within 15 generations if they were 1.4 times as likely as the locals to reproduce and the intermarriage rate was 7%. By keeping the intermarriage rate low, the Anglo-Saxons preserved their elite status and reproductive advantage.

    Thomas and colleagues note that their conclusions, published online 19 July in the Proceedings of the Royal Society B, are consistent with old laws that gave Anglo-Saxons higher social and economic status. “This is an exciting new contribution,” says Alex Bentley, an anthropologist at the University of Durham, U.K. It shows that “culture has had real, measurable effects on human genetic history.”


    The habitat occupied by tigers in Asia has dwindled by 40% since 1995, and the animals now range over only 7% of their original habitat, according to a report released last week at the National Zoo in Washington, D.C. “Wild tigers are slipping away from us,” said Eric Dinerstein of the World Wildlife Fund, lead author of Setting Priorities for the Conservation and Recovery of Wild Tigers: 2005–2015, a report compiled by government and conservation groups.

    The report combines current data on human land use and tiger habitats with on-the-ground tiger evidence. It identifies 76 “tiger conservation landscapes” in 13 Asian countries where conservation efforts are most likely to be productive.


    Two extremes—Adams (left) and Harding.

    In terms of intellect, John Quincy Adams, the sixth U.S. president, is the chief commander in chief, according to a new study that estimates the intelligence quotients (IQs) of all 43 U.S. presidents.

    For the rankings, psychologist Dean Simonton of the University of California, Davis, who does research on intellect and leadership, drew on studies by other researchers as well as history. Sources included IQ estimates that were based on the ages at which presidents reached intellectual milestones such as learning to read, accounts about their intellectual curiosity, and descriptions of the leaders' personality traits. Based on the descriptions, Simonton created anonymous profiles of all the presidents and asked a panel of research assistants to score each on traits associated with intelligence, including curiosity, insightfulness, and inventiveness.

    John Quincy Adams's IQ was estimated at about 170. Other smarty-pants include Thomas Jefferson, John F. Kennedy, and Bill Clinton, Simonton reports in the August issue of Political Psychology. And what of the current leader of the United States? George W. Bush's IQ score is probably about 125, which puts him in the upper range of college graduates but low among presidents. Warren Harding—who “by his own admission was not smart enough to be president,” Simonton says—was the only 20th century president to get a lower estimate. Such rankings are imprecise given the gaps in the data, says Douglas Detterman, an intelligence researcher at Case Western Reserve University in Cleveland, Ohio. Even so, he says, Simonton's approach seems reasonable.