Where We Come From
Recent advances in genetics are starting to illuminate the wanderings of early humans
Andy Carvin is a pioneer on the strange frontier of DNA genealogy. The 29-year-old Internet policy analyst had built his family tree back to ancestors in Busk, Ukraine, but that's where the trail went cold. Then he read about research tracing the Y sex chromosome, which is passed intact from father to son, all the way back to the time of Aaron, the single progenitor of the priestly cohen caste 3,000 years ago. More than once, his father had told him their family was cohanim. "I was really curious," Carvin says, "to see if there was even a small possibility that the oral tradition was true."
On the Internet, Carvin located Family Tree DNA, a small Houston firm created to answer such questions. He mailed in a sample of his DNA, gathered by swabbing the inside of his cheek, and waited. In late October, he got a call from Bennett Greenspan, president of Family Tree DNA. Not only did his Y chromosome have the cohanim markers--small genetic variations--but other markers matched with those of another man in the database, making it likely that they share a forefather within the past 250 years.
So, just before Thanksgiving, Carvin set off on a DNA-induced family reunion. He took the train from his home in Washington, D.C., to Philadelphia and met Bill Swersky, a 59-year-old federal official. "We immediately hit it off," says Carvin. "I felt like I was visiting one of my uncles." Over smoked whitefish and bagels, they paged through family photos. Andy's dad looks like Bill's father. Bill's son looks like Andy when he was younger. "He's a hell of a lot better looking than I am," Swersky says of his new relative. "I'm jealous."
It's exceedingly unusual to find such treasure in the genetic attic. Humans are very much alike genetically, with most of the variation within--rather than between--ethnic groups. Carvin and Swersky struck gold because they're part of the small cohanim group, which is itself a subset of an insular group, Jews. Finns, Sardinians, and Basques are among other groups with small founding populations that also have highly distinctive genetic pedigrees. By contrast, most people of European origin are so genetically mixed that it's impossible to tell German from Frenchman, Bosnian from Serb.
But the tools of biotechnology have become so powerful that it's now possible to deduce ancient human history from a drop of blood or a few shed skin cells. This molecular view of the past is already being employed to trace the cause of ailments such as cancer and heart disease, as well as aiding individuals like Carvin in tracking their roots. Most significantly for scientists studying past human life and culture, it offers the best insight yet into the abiding mystery of how modern Homo sapiens arose out of archaic hominids who first left Africa about 1.7 million years ago. "It's a very exciting time," says Colin Renfrew, a professor of archaeology at the University of Cambridge. "In the next 10 years the whole course of early human history is going to become very much clearer."