“Early Observations of Genetic Diseases”, Maik Urban1999-12 (heritability)⁠:

In 1902 Archibald E. Garrod published an epidemiological study in The Lancet in which he proposed that alcaptonuria had a recessive mode of transmission that followed Gregor Mendel’s principles. With this milestone, the connection had been made between a human disease and the laws of inheritance published by Mendel in 1865. Since then our knowledge of genetically determined diseases has increased explosively.

…The recurrence of specific signs in successive generations in a given family had been observed by naturalists and physicians long before Mendel’s time. Pierre Louis Moreau de Maupertuis, who under Frederick the Great was president of the Berlin Academy, published in 1752 the pedigree of a family in which isolated hexadactyly occurred in 4 generations. He also showed that this minor malformation could be transmitted to their children by either parent. [The first true pedigree?] But the mechanism of inheritance remained a mystery for doctors until 1900.

See Also:

• The Debate Between Two of the Founders of American Psychiatric Genetics, Aaron Rosanoff and Abraham Myerson, on Mendelian Models for Psychiatric Illness (1911^–₆1917_107ya)

• The Prehistory of Psychiatric Genetics: 1780^–₁₃₀1910_114ya

• Theory and Method: An Analysis of European and American Animal Breeding Practices, from the 18^th to the 21^st Century

• Imre Festetics and the Sheep Breeders’ Society of Moravia: Mendel’s Forgotten ‘Research Network’