"The Mixed-Up Brothers of Bogotá"

"Jorge moved to his desktop computer so he could see the images more closely. He clicked once more on the photo of William and the friend holding shot glasses. Now that the image was large, he could examine what he had failed, incredibly, to notice when he looked at the photo on his phone. He leaned in close, his nose practically touching the screen. The man’s hair was slicked up like a rooster’s crown, and the shirt was all wrong. But there was the full lower lip and thick brown hair that Jorge knew well. The buttons on the man’s shirt were straining slightly at the hint of a potbelly, in a way that was intimately familiar. Jorge felt a rush of confusion, and then his stomach dropped. The friend sitting next to his double had a face that Jorge knew better than his own: It was the face of his fraternal twin brother, Carlos...

Immediately, Wilber saw, with total clarity, what it took everyone else hours to grasp.

‘‘So we were swapped,’’ Wilber said, shrugging, annoyed by the sense of momentousness William seemed to want to attach to the photo. ‘‘I don’t care who they are. You’re my brother, and you’ll be my brother until the day I die."...

The meta-­analysis published this spring in Nature Genetics, which examined 50 years of studies of twins, arrived at a conclusion about the impact of heredity and environment on human beings’ lives. On average, the researchers found, any particular trait or disease in an individual is about 50 percent influenced by environment and 50 percent influenced by genes. But that simple ratio does not capture our complicated systems of genetic circuitry, the way our genes steadily interact with the environment, switching on, switching off, depending on the stimulus, sometimes with lasting results that will continue on in our genome, passed to the next generation...

Segal and Craig were eager to see the epigenetic results for the Colombian twins. Whose epigenetic profile, they wondered, would look more alike? The biologically unrelated twins who shared an environment — Segal calls them virtual twins — or the ones whose DNA was the same?

A sample of four subjects could only raise questions, not answer them."
http://www.nytimes.com/2015/07/12/magazine/the-mixed-up-brothers-of-bogota.html?_r=0

This was a really interesting read, an exploration not only of the unusual circumstances of these brothers, but of variation in human personalities and emotional needs, and great writing about genetics.