Evolutionary Genetics: Progress and Challenges

Genetics plays a central role in evolutionary biology, because only heri-table traits can evolve. Evolution by natural selection can be succinctly described as a consequence of heritable fitness variation among individuals of a population. Charles Darwin clearly understood that a mechanism of inheritance and a source of heritable variation were necessary components of a complete theory of evolution, but both were unknown to him. Although he thought that much heritable variation arises without reference to need, he also thought that traits acquired during the lifetime of an organism could be passed on to the next generation and used this idea of Larmarck-ian inheritance to formulate his theory. It is of significant historical interest that the revolutionary experiments that eventually led to the revelation of the true mechanism of inheritance had already been continuing for 3 years when Darwin published The Origin of Species. Gregor Mendel performed his famous series of pea cross experiments between 1856 and 1863. In 1865, Mendel read his paper entitled, " Experiments On Plant Hybridization, " at two meetings of the Natural History Society of Brno. When Mendel published his work in the Proceedings of the Brno Natural History Society (1866), he described particulate inheritance in the form of three basic laws: segregation , independent assortment, and dominance. Unfortunately, Mendel's work was unrecognized by the scientific community for the next 34 years, until it was rediscovered in 1900 by Hugo de Vries, Carl Correns, and Erich von Tschermak. The three Mendelian laws of inheritance were later integrated with the chromosomal theory of inheritance, which was developed by Thomas Morgan and colleagues in the 1910s, and formed the core of classical genetics. It is interesting to ask why Darwin did not know about Mendel's work. First, there is no evidence that Darwin subscribed to the Proceedings of the Brno Natural History Society. Second, there were apparently only 11 published references to Mendel's name before 1900, but at least 3 of these references were accessible to Darwin. One of them was in the Royal Society's