And that evidence could not be measured by a DNA marker.… When Aya’s daughter was born, there was one fact in the delivery room that required no laboratory test. Aya was the person who had given birth. The question of the father was different. For centuries, people had tried to answer it indirectly. A newborn’s nose resembled the father’s. The baby’s eyes looked like the grandfather’s. Perhaps the parents shared a particular blood type, and the child had inherited a combination that seemed to fit. But resemblance is not proof, and blood groups are much better at excluding some biological relationships than confirming a particular father. Two unrelated men can have similar faces, and millions of people share the same common blood-group combinations. Aya’s husband, Ren, had never questioned that he was the father. Then, during a routine family discussion, someone casually mentioned genetic testing. The suggestion unsettled hi...