One of the aspects of genetics which I think tends to reoccur is that people have a fixation on the two extreme ends of visible genetic inheritance. On the one hand you have discrete Mendelian or quasi-Mendelian traits where most of the variation is controlled by only a few genes, and which may exhibit dominance\/recessive expression patterns. And you also have the classic quantitative traits which exhibit continuous variation and a normal distribution. Mendelism leads to strange ideas about atavism\/throwbacks, and a promiscuous utilization of the idea of dominance\/recessivity (e.g., “non-white genes are dominant to white genes”). Continuous traits are more comprehensible in their confusion, as they are the intuitions which led to the models of “blending inheritance” which were in the air before the triumph of Mendelian genetics in the first decade of the 20th century. But they lead to the logical inference that variation should slowly “blend away” through admixture. This was a major problem with 19th century models of evolution through natural selection; blending eliminated the variation which was necessary for the action of selection to be effective. A blending model also explains why there is a common perception that racial admixture will lead to the elimination ...<\/p>","protected":false},"excerpt":{"rendered":"
One of the aspects of genetics which I think tends to reoccur is that people have a fixation on the two extreme ends of visible genetic inheritance. On the one hand you have discrete Mendelian or quasi-Mendelian traits where most … Continue reading