Nancy Segal (Deliberately Divided: Inside the Controversial Study of Twins and Triplets Adopted Apart) is an evolutionary psychologist, behavioral geneticist, and author. Nancy joins the Armchair Expert to discuss whether there’s anything predictable about a twin who comes out first, why in twin studies differences are not deficits, and her work with the Minnesota Study of Twins Reared Apart. Nancy and Dax talk about the unexpected reason identical twins are more alike that any other pair of people, the concept of inclusive fitness to explain differential genetic behavior, and why doppelgängers can be an effective test for criticism of twin research. Nancy explains her argument that twins fundamentally challenge how we think the world works, the remarkable fact that children born on the same day to two sets of identical twins are genetic fraternal twins, and why only identical twins raised apart are able to see themselves in a life unlived.

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