The Jukes and the Kallikaks were pseudonyms for two families used as examples during the latter 19th century and early 20th century to argue that there was a genetic disposition toward anti-social behavior or low intelligence. The arguments were used to bolster advocacy of eugenics, or the pseudo-scientific breeding of human beings, by demonstrating that traits deemed socially inferior could be passed down from generation to generation.
As a general concept the Jukes Family represented inherited criminality and the Kallikak Family inherited mental retardation.
The Jukes family was described by Richard L. Dugdale in 1877 in The Jukes: A Study in Crime, Pauperism, Disease and Heredity. A follow-up to Dugdale's work was published by Arthur H. Estabrook of the Eugenics Record Office at Cold Spring Harbor, New York in 1916 as The Jukes in 1915. This latter work studied 2,820 persons, including 2,094 descendants of the original six Juke sisters. In the early 1950s these studies were presented in sociology and psychology textbooks in such a manner as to leave the student or reader with the distinct impression that families with these names actually existed. That impression was fortified by the oft used reference to many descendants of "the original six Juke sisters". These same text books also characterized homosexuality as a mental illness.
The Kallikak family was described by Henry H. Goddard in 1912 in The Kallikak Family: A Study in the Heredity of Feeble-Mindedness.
The Zeros, the Nams, the Happy Hickories, the family of Sam Sixty (named for Sam's IQ) and the Doolittles were other family aliases used in similar works of the late 19th and early 20th centuries. The researchers chose those pseudonyms to reflect the nature of the abnormalities they documented.