Sam Kean, author of ‘Violinist’s Thumb,’ on genes and how they affect who we are

Ehlers-Danlos syndrome is a rare conglomeration of connective-tissue disorders. Symptoms include migraines, easily bruised skin, resistance to anesthetics and, most markedly, hyper-flexible joints that bend in ways bordering on the grotesque. I know all of this because I have become convinced — in the obsessive, giddy way of hypochondriacs — that I have Ehlers-Danlos syndrome. I have become convinced of this because I have just finished reading “The Violinist’s Thumb.”

“All right,” Sam Kean says, settling into a small booth at a Panera in the District. “Show me what you can do.”

(Bill O'Leary/WASHINGTON POST) - Kean was raised in South Dakota before moving to Washington. He has that Midwestern matter-of-factness to the way he speaks, tinged with nerd-boy excitement when the topic is genetics.

(Little, Brown and Company) - ”The Violinist's Thumb” by Sam Kean.

I can bend my wrist down to my forearm. I can wrench my fingers backward until they rest on my hand. A hitchhiker’s thumb might arc into a 90-degree angle; mine will go to 135.

Kean appraises my impromptu circus freak show. “Hmm,” he says. “Hmm.”

Kean is 33, slightly built, shaggy-haired. He is the author of “The Violinist’s Thumb,” a freshly published romp through the history of genetic science and the double helixes that make up our personhood. Like Kean’s 2010 bestseller “The Disappearing Spoon,” which was a mash note to the periodic table of elements, “The Violinist’s Thumb” is a loosely jointed collection of true stories. [Loose joints: Also a symptom of Ehlers-Danlos syndrome!]

We have come to this Panera to have a loosely jointed conversation about DNA, which is really a conversation about who we are — which is really a conversation about how obsessed we are with who we are. Witness the popularity of NBC’s celebrity genealogy show “Who Do You Think You Are?” or the rampaging success of “The Immortal Life of Henrietta Lacks.” (If we’re splitting hairs — and since we’re splitting cells, we might as well — we’d note that that book wasn’t about immortal life so much as it was about immortal cell lines.)

In Kean’s book, one encounters the debonair Fly Boys, whose grody work — they bred fruit flies — informed our understandings of genetic heredity. One encounters 19th-century violinist Niccolo Paganini, whose extraordinarily bendy thumbs gave Kean’s book its title. His flexibility made him a virtuoso, but it might have been a symptom of Ehlers-Danlos, the genetic abnormality that hastened his death.

“I’m kind of a sucker for the retro-diagnoses,” Kean says.

Take, for example, King Tut. Through DNA, we’ve learned that the boy king had a cleft palate, a club foot and a truckload of other medical anomalies. His parents, it turns out, were brother and sister.

Or take King Tut’s incestuous father. For a long time, archaeologists wondered if Akhenaten, too, had some kind of illness. “You look at drawings of Akhenaten, and he looks very strange,” Kean says. “He has this elongated head and enormous lips. Sometimes, he has huge buttocks or a potbelly.”

Maybe he was just ugly? I ask.

“No — not just a little off, but very off.” So scientists did a CT scan and some genetic tests. It turns out Akhenaten looked completely normal.

The big butt, the stretchy head — all of it was an artistic costume designed to give the pharaoh some of the physical qualities commonly attributed to gods. The weird body was propaganda; the scientific speculation had been just guesswork.