Wilhelm Weinberg's early contribution to segregation analysis.

Wilhelm Weinberg (1862-1937) is a largely forgotten pioneer of human and medical genetics. His name is linked with that of the English mathematician G. H. Hardy in the Hardy-Weinberg law, pervasive in textbooks on population genetics since it expresses stability over generations of zygote frequencies AA, Aa, aa under random mating. One of Weinberg's signal contributions, in an article whose centenary we celebrate, was to verify that Mendel's segregation law still held in the setting of human heredity, contrary to the then-prevailing view of William Bateson (1861-1926), the leading Mendelian geneticist of the time. Specifically, Weinberg verified that the proportion of recessive offspring genotypes aa in human parental crossings Aa × Aa (that is, the segregation ratio for such a setting) was indeed p=1/4. We focus in a nontechnical way on his procedure, called the simple sib method, and on the heated controversy with Felix Bernstein (1878-1956) in the 1920s and 1930s over work stimulated by Weinberg's article.