Final answer:
Dr. Alfred Kinsey of Indiana University researched the postpartum sex taboo and published his findings in books on human sexuality.
Step-by-step explanation:
The research on the postpartum sex taboo was primarily conducted by Dr. Alfred Kinsey of Indiana University. In the late 1940s, Kinsey initiated large-scale survey research on human sexuality, which included studying the attitudes and behaviors surrounding postpartum sex. Kinsey's findings were published in his books, Sexual Behavior in the Human Male and Sexual Behavior in the Human Female, and they contributed to a more open dialogue on sexual topics.