This paper inquires into the very possibility of the units of selection debate’s origin in the problem of altruism, function in articulating the evolutionary synthesis, and philosophical status as a problem in clarifying what makes something a level or unit of selection. What makes the debate possible? In terms of origins, there are a number of logically possible ways to deviate from the model of Darwinian individual selection to explain evolved traits. In terms of function, adherence to the evolutionary synthesis (...) yields norms which restrict these possibilities to a manageable few. In terms of philosophical status, the abstract structure of selection mechanisms permits a causal construal, on which the unit of selection is identified with the “unit of possession”, that which possesses the causally efficacious trait selected for. It also allows a teleological interpretation, on which the unit of selection is identified with the “unit of benefit”, that for the sake of which the causally efficacious trait is selected. It is proposed that a unit of selection is really a pair of units, consisting of both a unit of possession and a unit of benefit. (shrink)

A set of constraints forces trade-offs which prevent us from achieving the best possible definitions of the ‘level’ and ‘unit’ of natural selection. This set consists in decisions concerning conflicting pre-analytic intuitions in problematic cases, the relative roles of various conceptual resources in the definitions, which facts need to be accounted for using the definitions, how the relation between selection and evolution orients the definitions, and the relation between the level and unit concepts. Systematic reconstruction and evaluation of leading analyses (...) along these dimensions favors a new functional analysis over Williams’ consequentialist analysis, Sober’s causal analysis, and Dawkins’ teleological analysis. (shrink)

Evolutionary psychology is a science in the making, working toward the goal of showing how psychological adaptation underlies much human behavior. The knee-jerk reaction that sociobiology is unscientific because it tells “just-so stories” has become a common charge against evolutionary psychology as well. My main positive thesis is that inference to the best explanation is a proper method for evolutionary analyses, and it supplies a new perspective on the issues raised in Schlinger's (1996) just-so story critique. My main negative thesis (...) is that, like many nonevolutionist critics, Schlinger's objections arise from misunderstandings of the evolutionary approach.Evolutionary psychology has progressed beyond telling just-so stories. It has found a host of ingenious special techniques to test hypotheses about the adaptive significance and proximate mechanisms of behavior. Naturalistic data using the comparative method combined with controlled tests using statistical analyses of data provide good evidence for a variety of hypotheses about behavioral control mechanisms — whether in nonhumans or in humans. For instance, the work of Gangestad and Thornhill on evolved mate preferences and fluctuating asymmetry of body type (FA) is a model of success. As the quantity and quality of evidence increase, we are entitled not just to regard such evolutionary hypotheses as preferable, but also as true. Such studies combine to show that the best explanation of “the psychic unity of humankind” — common patterns across societies, history, and cultures exposed by evolutionists — is the gendered, adapted, evolved species-typical design of the mind. (shrink)