Selection Experiments as a Tool in Evolutionary and Comparative Physiology: Insights into Complex Traits--an Introduction to the Symposium.

‘‘The whole organism is so tied together that when slight variations in one part occur, and are accumulated through natural selection, other parts become modified. This is a very important subject, most imperfectly understood.’’ (Darwin, 1859, The Origin of Species). ‘‘Hence if man goes on selecting, and thus augmenting, any peculiarity, he will almost certainly modify unintentionally other parts of the structure, owing to the mysterious laws of correlation.’’ (Darwin, 1859, The Origin of Species). ‘‘Biological reality is so complex that we are very far from any reasonably mechanistic understanding of evolutionary processes.’’ (Felsenstein, 1988, p. 468) ‘‘Apparent complexity usually means a lack of understanding.’’ (McCarthy and Roberts, 1989, p. 134)