In his paper "The average contribution of each several ancestor to the total heritage of the offspring," published in the Proceedings of the Royal Society 61 (1897) 401-413, English polymath Francis Galton published his “Law of Ancestral Heredity,” based on both human and basset hound pedigrees. Galton first proposed the law in 1876, and revised it several times over the next two decades. His basic conception was that on average, parents provide offspring with half of inherited traits, grandparents contribute one quarter, great grandparents one eighth, and so on.
"The "law of ancestral heredity," as it turned out, was mistaken. Although he was interested in individual variations, Galton's mathematical methods treated them as "errors." In Gregor Mendel's more carefully conceived experiments with culinary peas, variations represented the expression of discrete alternative factors or (as we would say today) genes. Galton, in his personal correspondence with Darwin, came close to this conception, but never proceeded to a testable formulation." (http://www.genomenewsnetwork.org/resources/timeline/1876_Galton.php,)
J. Norman (ed) Morton's Medical Bibliography 5th ed (1991) no. 239.