Introduction to molecular population genetics

The study of evolutionary biology is commonly divided into two components: study of the processes by which evolutionary change occurs and study of the patterns produced by those processes. By “pattern” we mean primarily the pattern of phylogenetic relationships among species or genes. Studies of evolutionary processes often don’t often devote too much attention to evolutionary patterns, except insofar as it is often necessary to take account of evolutionary history in determining whether or not a particular feature is an adaptation. Similarly, studies of evolutionary pattern sometimes try not to use any knowledge of evolutionary processes to improve their guesses about phylogenetic relationships, because the relationship between process and pattern can be tenuous. Those who take this approach argue that invoking a particular evolutionary process seems often to be a way of making sure that you get the pattern you want to get from the data. Or at least that’s the way it was in evolutionary biology when evolutionary biologists were concerned primarily with the evolution of morphological, behavioral, and physiological traits and when systematists used primarily anatomical, morphological, and chemical features (but not proteins or DNA) to describe evolutionary patterns. With the advent of molecular biology after the Second World War and its application to an increasing diversity of organisms in the late 1950s and early 1960s, that began to change. Goodman [2] used the degree of immunological cross-reactivity between serum proteins as an indication of the evolutionary distance among primates. Zuckerkandl and Pauling [16] proposed that