PopSci's 2nd Annual Brilliant 10

SARAH TISHKOFF


Molecular Anthropology: U. of Maryland, College Park


From the genes of living people, she divines the story of human origins.



Sarah Tishkoff realized how far she'd strayed from the scientific mainstream when she found herself processing blood samples in a centrifuge she'd hooked to the battery of her dusty Land Rover near a village in the Ngorongoro district of Tanzania. Tishkoff, 37, searches for human origins not by hunting for ancient skulls but by examining the "fossils" in our genome: genetic mutations that are passed down through the generations.



While still a student at Yale Medical School, Tishkoff developed a novel way to analyze DNA from living people's blood. Then, by determining the frequency of mutations in DNA from various populations, she was able to conclude that African lineages are the oldest on Earth and that at some relatively recent time in the past, a small group of people migrated out of East Africa and populated the rest of the world. Her work buttressed the reigning theory of human origins that had been developed in the traditional fashion—by using
radioisotope dating to determine the ages of ancient
human bones found in Africa and elsewhere.



Tishkoff had few African DNA samples to work with, so in 2001 she headed into the bush to collect blood from as many tribal groups as possible. Map in hand, she spent days traveling between far-flung villages. At night she processed blood in her car-battery-operated centrifuge. She slept in a truckers' guesthouse and was invited into the homes of Maasai herdspeople. She won over tribespeople and wary government officials. "It was the most exciting thing I've ever done," she says. Tishkoff's new database recently yielded a key insight: Several populations thought to have originated in northeastern Africa are ancient, dating back 90,000 years. This finding too reinforces traditional detective work into the origins of modern humans: Paleontologist Tim White of UC Berkeley reported in June that three Homo sapiens skulls found in Ethiopia are the oldest known.


—Laurie Goldman