INTRODUCTION

Population genetics is a subfield of evolutionary biology that aims to represent mathematically the changes in the genetic variation of populations (specifically, sexually reproducing populations with Mendelian heredity) over time. The mathematical models of population genetics provide a theoretical basis for experimental studies of laboratory populations and studies of natural populations. Our primary focus in this essay is on population genetics theory itself, rather than its applications, although towards the end of the essay we give some discussion of the latter.

Population genetics attempts to measure the influence of the causes of evolution, namely, mutation, migration, natural selection, and random genetic drift, by understanding the way those causes change the genetics of populations. But how does it accomplish this goal? We begin in Section 2 with a brief historical outline of the origins of population genetics. In Section 3, we sketch the model theoretic structure of population genetics, providing the flavor of the ways in which population genetics theory might be understood as incorporating causes. In Sections 4 and 5 we discuss two specific problems concerning the relationship between population genetics and evolutionary causes, namely, the problem of conceptually distinguishing natural selection from random genetic drift, and the problem of interpreting fitness. In Section 6, we briefly discuss the methodology and key epistemological problems faced by population geneticists in uncovering the causes of evolution. Section 7 of the essay contains concluding remarks.