Beyond Empathy

Of the many uses to which we put twins, from plot devices to product mascots to literary symbols, the most problematic is the scientific twin study. Often considered a gold standard when investigating an aspect of the human condition, twins have been the subject of studies of autism, attention deficit hyperactive disorder and anxiety—to name only a few of the conditions starting with A. Sadly, investigators with more ambition than humanity have been known to treat twins abominably. A repugnant recent example is John Money, the fraudulent sexologist who attempted to reassign the gender of one of a pair of identical twin boys, resulting in the eventual suicide of both twins.

But in the annals of twin exploitation, Josef Mengele, the Nazi physician who spared twins from the Auschwitz crematorium in order to use them as nothing more than the contents of a Petri dish, will remain the most repulsive. Although nearly all of the 3,000 twins he experimented on perished, the...