Animal genetics 100 years ago.

One hundred years ago, the first book with the phrase "Animal Genetics" in its title was published. It was written by F.A.E. Crew, then Lecturer in Genetics and foundation Director of the Department of Research in Animal Breeding at the University of Edinburgh. The 352 pages of text provide a most interesting summary of the knowledge of animal genetics at that time. It is impressive to see the extent to which the understanding of genetics had developed in just a couple of decades since the rediscovery of Mendelism. There was, for example, recognition that genes are borne on chromosomes; that XX/XY sex determination provides a very satisfactory explanation for most of the relevant evidence; that sex-linked inheritance has a practical application; that variation in quantitative traits is determined by the combined action of many genes and many non-genetic factors; that inbreeding results in substantial decreases in fecundity and fertility due to homozygosity for undesirable alleles; that crossing between lines or breeds gives rise to hybrid vigour (heterosis); and that many disorders are inherited in a Mendelian fashion, and hence can be controlled by informed breeding. There is, however, no mention of Fisher's 1918 paper nor of Wright's recently published inbreeding coefficient and coefficient of relationship. Crew's book inspired the next generation of geneticists, such as Fred Hutt, who travelled from Canada to Edinburgh to do a PhD with Crew, and who later published his own very influential book with the same title, which was dedicated to Crew.