The Genographic Project focuses on the Y chromosome in males, which is handed down intact from father to son, and on mitochondrial DNA (mtDNA), which a mother passes to her offspring. Over generations, small, harmless mutations accumulate on these two snippets of DNA; to Wells and other scientists these genetic markers constitute a history book. As ancient human populations migrated out of Africa, splitting off from each other and entering new lands, they accumulated different patterns of markers that reflect that history. Each individual today retains such a pattern.
In recent centuries those prehistoric paths have reconnected in New York and other immigrant havens. “From the beginning of the project,” Wells says, “I’ve wondered if it would be possible to sample all the major lineages on Earth on a single street.” On 30th Avenue he almost did—the 193 volunteers turned out to be carrying genetic markers for virtually all the major migrations that peopled the continents. The only missing lineage was the oldest one, which Genographic scientists found in Khoisan hunter-gatherers in southern Africa; their ancestors initially diverged from other modern humans more than 100,000 years ago.
The DNA of small, relatively unmixed groups like the Khoisan still preserves clear signals of their unique population histories. In places like Queens, where people from around the world have been swapping DNA for generations, those histories are being lost; a Y chromosome, say, doesn’t reflect the whole ancestry of its owner, let alone of a population. If the Genographic Project usually targets populations that have so far escaped the melting pots, it’s precisely because those pots are such a rich confusion of genes.
“Everybody talks about Astoria like it's Greek,” says George Delis, a retired community manager and a Greek immigrant himself. “Well, it’s not Greek. It’s everything.” —Jamie Shreeve