University of Pennsylvania

Gene trekking

Science | African genes showcase diversity

Issue: "Tiananmen massacre," June 6, 2009

After 10 years of collecting blood samples and analyzing DNA-sometimes extracted in the field with portable, car battery-operated centrifuges-researchers have produced the most extensive survey of African genetics in history. The results prove Africa to be the most genetically diverse continent in the world, meaning no local population of Africans is rightly representative of the rest.

Sarah Tishkoff, a University of Pennsylvania geneticist who led the study, explained that diversity occurs when groups of people live separately for long periods of time. Among the biggest surprises to her: Most Africans can be traced to multiple ancestry groups, suggesting past migrations once mixed the now-distinct populations.

African-Americans who participated in the survey were broadly linked to populations of West Africa. Some groups that have traditionally led hunter-gatherer lifestyles, such as Pygmies and Khoesan-speakers (who incorporate "clicking" sounds in their language), were also related, although they now live hundreds of miles apart.

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Besides their interest in human origins and migration, the researchers want the medical community to use their information to understand how certain groups are more susceptible to diseases like cancer, HIV, and malaria-and to determine which drugs they'd best respond to.

Old bones

By Daniel James Devine

After hauling a 750-pound chunk of sandstone and fossil out of a Montana dig site on the back of an old truck hood, paleontologist Mary Schweitzer rushed it to a lab and discovered what she already suspected: The fossilized femur, that of a duck-billed dinosaur called a hadrosaur, contained a soft core. Careful analysis revealed proteins for blood vessels and for collagen, a connective tissue. The timeline of evolution would place the fossil at 80 million years old.

Schweitzer and her colleagues first discovered soft dinosaur tissue in 2005, in a T. rex femur. At the time, the paleontology community greeted the announcement with deep skepticism because a fossil more than a million years old wasn't expected to have any original organic material left in it. Critics said the alleged tissue must be some form of contamination. Schweitzer proposed theories of tissue preservation, while young-earth creationists said the proteins called into question the fossil's real age.

Schweitzer and her colleagues upheld even more rigorous standards for their study of the hadrosaur, published May 1 in the journal Science. They took pains to avoid contaminating the fossil and confirmed the presence of proteins through independent labs. They say their results show that soft tissue preservation may not be uncommon.

Lab notes

By Daniel James Devine

Lab notes Energy: Under the Obama administration's fiscal 2010 budget, funding will be cut off for the development of the fuel cell in hydrogen cars. Energy Secretary Steven Chu said spending on land-based fuel cell technology will continue, but that hydrogen-powered vehicles-first funded under President George W. Bush-aren't proving themselves practical.

Sociology: Popular belief says cloudy weather will influence suicide rates, but the 24-hour sunlight of Arctic ­summer days may be a more accurate predictor. Over three decades of suicide data from Greenland shows that the prevalence of suicide peaked in June and dipped in winter. Ruling out other factors, researchers think reduced sleep could play a role.

Daniel James Devine
Daniel James Devine

Daniel is managing editor of WORLD Magazine and lives in Indiana. Follow Daniel on Twitter @DanJamDevine.


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