Version: v1, Published online: 2012
Retrieved February 20, 2019, from https://www.rep.routledge.com/articles/thematic/biological-function/v-1
Biologists ascribe functions to biological traits. For example, they tell us that it is the function of the heart to pump blood and that it is a function of the pancreas to control blood glucose levels. Philosophers attempt to understand the nature of these function ascriptions and their role in biology. Such function ascriptions are prima facie puzzling since they seem to be teleological and normative: teleological because they seem to tell us what something is for; normative because they underwrite claims about systems functioning properly or about dysfunction.
There are a number of theories of function available. Those with most currency in philosophy of biology attempt to naturalize the notion of function and so they reject the idea that it is irreducibly value-laden or that it must involve the idea of divine design. Four influential theories are as follows. The etiological theory says that the function of a phenotypic trait is what it was selected for (e.g. by natural selection). The systemic theory says that functions are capacities to contribute to complexly achieved capacities of containing systems. The propensity theory says that functions are contributions to fitness that make traits apt for future selection. And a statistical theory says that normal functions are statistically typical contributions to fitness.
Two different types of functional explanation are operational and remote (or evolutionary) explanations. Operational explanations ascribe functions to a system’s parts to explain how the system operates. They answer questions of the form, ‘how does this work?’ Evolutionary explanations explain the ‘rationale’ of a trait, why it was preserved in the population. They answer questions of the form, ‘why is this here?’ or ‘why did this evolve?’ Some philosophers claim that distinct notions of function are used in these two types of explanation.
Neander, Karen. Biological function, 2012, doi:10.4324/9780415249126-Q140-1. Routledge Encyclopedia of Philosophy, Taylor and Francis, https://www.rep.routledge.com/articles/thematic/biological-function/v-1.
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