So, decades later, I asked a third cousin who shares this paternal line with me to get tested: If our sequencing matched, my great-grandfather hadn’t been adopted, and like Queen Victoria, Edgar Allan Poe, and Charles Darwin before him, he’d kept it in the family. This genetic test analyzed something called Y-DNA. Basically, it works like this: You, your father, your grandfather, your great-grandfather, and every prior ancestor in your direct male lineage are connected by a nearly identical strand of genetic code, like a fence line extending beyond the horizon. This code lives in your Y chromosome; the last fence post is Adam.
To those of us who failed sophomore biology, having your Y-DNA put under the microscope can sound intimidating. But it’s surprisingly easier and, frankly, much cooler than trolling Ancestry.com like your Aunt Wanda’s been doing for the past decade. All you do is swab your cheek, mail the collection kit to a company like Family Tree DNA in Houston, and wait for an e-mail. What you get back is an incredible piece of personal history—the route your paternal line took when humanity began migrating from Africa about 60,000 years ago. (You might be descended from a great warrior: About 8 percent of men in Central Asia can trace their paternal line back to one male who lived roughly 1,000 years ago. It’s almost certainly Genghis Khan, who died 788 years ago and whose sons and grandsons no doubt used the family name to make the acquaintance of vast numbers of women wearing pelts.)
Which is why more guys are going under the Q-tip. In 2000, the first year Y-DNA testing was available from Family Tree DNA, the company analyzed 1,500 samples; in 2014, it processed more than 50,000. Joshua Taylor, the 29-year-old cohost of Genealogy Roadshow on PBS, says the uptick can be explained, in part, by the fact that genetic testing allows a younger, more diverse demographic to be part of a movement it’s been shut out of, mainly because research sites rely heavily on Colonial and English records. “Gen Y has begun to trace its roots,” Taylor says. “It’s not like looking at a census record or a chart of your ancestry. It’s directly related to you.”
Even in sketching our own lines, we’re slowly revealing the branches of the global family tree. A.J. Jacobs, who’s writing a book about technology and genetics, is particularly intrigued by Y-DNA’s role in this, because it’s “so pure, the little part that doesn’t mix,” he says. He’s referring to the odd fact that only the Y’s tips combine with its partner, the X, so the Y’s center remains largely unchanged through aeons. This is what links you to Adam, the earliest male whose line survived. Geneticists thought they knew who Adam was, but they don’t: Two years ago, Family Tree DNA got a sample from an African-American in South Carolina named Albert Perry who descended from a man predating Adam by at least 60,000 years.
Almost certainly, your Y-DNA will fall squarely on the standard tree; results will yield your “deep” ancestry and a list of other men with identical or nearly identical Y’s. Unless they share your last name, they’re so distantly related, it hardly matters—though Craig Kanalley, a 29-year-old social-media manager for the NHL’s Buffalo Sabres, found Kennelly and MacNeely cousins in Ireland after having his Y-DNA tested, and he met one on a recent trip there.
Of course, not every discovery is celebrated over a Guinness. If you and a male relative get tested and don’t match, one of you had at least one “non-paternal” event in your line. This could be an acknowledged adoption—or a not-so-acknowledged scenario in which a cuckold raised another man’s kid. By one estimate, that happens in 2 percent of births in which the “dad” has no clue and in 30 percent of births in which he’s suspicious. A 34-year-old genealogist I know got so into Y-DNA analysis that he helped most of the males on his mother’s side get tested, discovered one didn’t match, and had to have an awkward conversation about decades-old rumors of an affair that the relative hadn’t heard about.
Nothing that dramatic happened when my cousin and I got our results. Our Y-DNA matched. My great-grandfather wasn’t adopted. The elderly genealogist who transcribed my great-grandfather’s death certificate for me had misread “Lincoln” as “Luncolias.” This made more sense: My great-grandfather was born in 1861, the year Abraham Lincoln took office. I can’t say the news shocked me. My family can be a little odd.
This article originally appeared in Details (March 2015).