Evolutionary psychology and behavior analysis are both committed to a scientific understanding of human behavior. This paper argues that--despite decades of mutual misunderstanding--greater convergence between these two theoretical orientations is now possible. Observations from evolutionary neurobiology, trait psychology, and behavior genetics allow us to move beyond old controversies. Keywords: Evolutionary psychology; Behavior Analysis; Behaviorism ********** It could be argued that many of the great leaps in human understanding occur when separate domains of inquiry are discovered to be united by some previously unsuspected commonality. Examples include; Descartes' unification of geometry and algebra (Singer, 1959) and the neo-Darwinian synthesis of natural selection and Mendelian genetics. In the latter case it is worth noting the acrimony that existed between Darwinians and Mendelians before the synthesis. The followers of Mendel had come to see inherited traits as discrete while the Darwinians thought in terms of continuous variation and tended toward Lamarckian notions of heredity. At the time these camps seem irreconcilable, yet the combined work of empirical investigators and mathematical theorists was able to create a powerful theory that embraced both Mendelian genetics and selection (Mayr, 1982). One wonders if such a synthesis is now possible between the discoveries of behavioral analysis and the insights of evolutionary psychology. There is a deep history of antagonism between these two approaches, which has reappeared in various guises over the last half century (e.g. Lorenz, 1965). It is not hard to find instances of misunderstanding and even incomprehension of the rival point of view. For example, Schlinger (1996) claims that: the problem with evolutionary explanations of behavior is that the evidence proffered to support them is so fraught with methodological problems that it is simply insufficient to warrant any conclusions about the role of genes and, thus, evolution (p. 75) While, Pinker's (2002) persuasive polemic for evolutionary and genetic influences on human behavior gratuitously, The Blank Slate, dismisses Skinner as a Maoist (p. 246). Skinner (1953) was certainly open to the possibility that genes and natural selection shape behavior. Skinner (1948), through the fictional Frazier, founder of Walden Two, argues: What is 'original nature of man?' I mean, what are the basic psychological characteristics of human behavior--the inherited characteristics, if any, and the possibilities of modifying them and creating others? That's certainly an experimental question--for a science of behavior to answer (p. 162). This statement is typical of Skinner's comments on this topic, he always admits that genes and evolution may play role, but is vague about what those influences might be or is skeptical about our ability to understand or study those influences. For example, in Science and Human Behavior he even seems favorably disposed to such unorthodox ideas as Huntington's (1938) climatic determinism and Sheldon's (Sheldon & Stevens, 1942) theory of somatotypes. Yet, just when he acknowledges these intriguing possibilities, he dismisses their relevance to the study of behavior: Even when it can be shown that some aspect of behavior is due to season of birth, gross body type, or genetic constitution, the fact is of limited use. It may help us in predicting behavior, but it is of little value in an experimental analysis or in practical control because such a condition cannot be manipulated after the individual has been conceived. The most that can be said is that knowledge of the genetic factor may enable us to make better use of other causes. If we know that an individual has certain inherent limitations, we may use our techniques of control more intelligently, but we cannot alter the genetic factor (Skinner, 1953, p. …