In today's encore excerpt--data on extramarital sex from Jared Diamond, UCLA professor, Pulitzer Prize-winning author, and winner of the National Medal of Science:
"People have many reasons to lie when asked whether they have committed adultery. That's why it is notoriously difficult to get accurate scientific information about this important subject. One of the few existing sets of hard facts emerged as a totally unexpected by-product of a medical study, performed nearly a half a century ago for a different reason. That study's findings have never been revealed until now.
"I recently learned those facts from the distinguished medical scientist who ran the study. (Since he does not wish to be identified in this connection, I shall refer to him as Dr. X.) In the 1940s Dr. X was studying the genetics of human blood groups, which are molecules we acquire only by inheritance. ... The study's research plan was straightforward: go to the obstetrics ward of a highly respectable U.S. hospital; collect blood samples from one thousand newborn babies and their mothers and fathers; identify the blood groups in all the samples; and then use standard genetic reasoning to deduce the inheritance patterns.
"To Dr. X's shock, the blood groups revealed that nearly 10 percent of those babies to be the fruits of adultery! ... There could be no question of mistaken maternity: the blood samples were drawn from an infant and its mother soon after the infant emerged from its mother. A blood group present in a baby but absent from its undoubted mother could only have come from its father. Absence of the blood group from the mother's husband as well showed conclusively that the baby had been sired by some other man, extramaritally. The true incidence of extramarital sex must have been considerably higher than 10 percent ... since most bouts of intercourse do not result in conception.
"At the time Dr. X made his discovery, research on American sexual habits was virtually taboo. He decided to maintain a prudent silence, never publishing his findings, and it was only with difficulty that I got his permission to mention his results without betraying his name. However, his results were later confirmed by several similar genetic studies whose results did get published. Those studies variously showed between 5 and 30 percent of American and British babies to have been adulterously conceived. Again, the proportion of the tested couples of whom at least the wife had practiced adultery must have been higher, for the same ... reasons as in Dr. X's study."
Jared Diamond, The Third Chimpanzee, Harper Perennial, Copyright 1992 by Jared Diamond, pp. 85-86.