Identical twins separated at birth and reunited as adults in a Minnesota twin study turned up with parallel careers, the same taste for Miller Lite, and, in one documented case, a childhood dog with the same name — the coincidences got the study famous, but they weren’t why it mattered

By the time the Minnesota Study of Twins Reared Apart wound up in 1999, 137 separated pairs had come through the lab, 81 of them identical. Niels Waller and colleagues ran 53 identical and 31 fraternal separated pairs through five measures of religious interests, attitudes and values, with several hundred reared-together pairs alongside them for comparison. Separated twins still shared a womb. A 2015 meta-analysis led by Tinca Polderman and Danielle Posthuma, published in Nature Genetics, swept up virtually every twin study of the previous fifty years: 17,804 traits, more than 14 million twin pairs. Separated pairs keep surfacing, too.