Martin later returned to Philadelphia, where he married a woman of the upper class and raised a family. The bar maid, meanwhile, gave birth to Martin's child and not-so-feeblemindedly named him Martin Kallikak Jr. As an adult, the fictitious Martin, Jr. was known as "Old Horror." Dr. Goddard reported that 143 of this man's descendants were feebleminded, and included prostitutes, alcoholics, people with epilepsy, and criminals.
Dr. Goddard traced the lineage of Martin Kallikak's family with his wife and found only successful, upstanding individuals of normal or better intelligence. Dr. Goddard's conclusion, which he published in a widely-read book entitled The Kallikak Family, was that mental retardation is hereditary and the root cause of many social problems.
Goddard's story was widely read because it said what people wanted to believe: that we had in our midst a group of people who, if allowed, will ruin the genetic strain. Goddard stated: "There are Kallikak families all about us. They are multiplying at twice the rate of the general population, and not until we recognize this fact, and work on this basis, will we begin to solve [our] social problems."
Goddard's book was eventually repudiated when his underlying research was exposed as scientifically invalid.