Telos vs. Natural Selection

Before the, let’s say, 17th century, accounts for why the world is the way that it is relied heavily on God’s intentions. For instance, the natural philosopher William Paley argued that:

  1. If you were to find a pocket watch in a field, it would be reasonable to suppose that some person designed the watch, since it would be extremely improbable for such an elegant and complex machine to occur by chance.
  2. Natural organisms, e.g. the human eye, are machines that are at least as elegant and complex as a pocket watch.
  3. Therefore, it is reasonable for us to assume that natural organisms were designed by some person (i.e. God), since it would be extremely improbable for such an elegant and complex machine to occur by chance.
So for Paley, the elegant design of natural organisms could only be accounted for by assuming that they were created by a designer, a conscious agent who created organisms for some purpose. The ancient Greek word for purpose is telos; a teleological account of something explains it in terms of how it serves some purpose. Whence the internet on which you are reading this essay? It was purposively designed by American scientists in order to communicate. Why is Obama in office? Because a majority of Americans (via the electoral college) thought he would better serve their respective agendas than Mitt Romney. Who is John Galt? He’s a talking prop which Ayn Rand invented to articulate her beliefs. Something is teleological insofar as it exists for some purpose.*

The reason I know about William Paley is that he’s used in undergraduate courses as Charles Darwin’s punching bag. Darwin is known as the father of evolutionary theory, although this is a little misleading: plenty of scientists in the mid-nineteenth century advocated adaptive evolution, i.e. the process by which organisms change to adapt to their environment. The problem was that there was no clear mechanism: how did e.g. a species suited to cold, dry climates change into a species suited to hot, wet climates?

Darwin’s mechanism was natural selection. It works like this: suppose you’ve got a population of pigeons living in a mostly-gray area. Suppose that about half of them are gray, and half of them are neon pink. Suppose that there are predators which try to eat the pigeons. It’s obvious that the neon pink pigeons will be more visible to the predators than the gray ones, and hence the neon pink pigeons will tend to die more often and more quickly than the gray pigeons. Over time, this will change the pigeon population: more gray pigeons will survive into adulthood (and hence be able to procreate even more gray pigeons) than neon pink pigeons. Eventually the pigeons will be entirely, or almost entirely, gray.

This is actually a pretty intuitive idea when you think about it. It basically says that organisms (or more properly, heredity-lines) which are successful at surviving and breeding will tend to survive and breed more, while those which aren’t very good at surviving and breeding will tend not to survive and breed, and will eventually die out. Natural selection is complemented by the idea of natural variation: the idea that members of a species tend to have slight differences (e.g. hair color), and if one of those differences causes them to become more (or less) likely to survive and procreate, then natural selection will make that difference become more (or less) widespread in the population.

As you can see, this process leads to organisms which have functions (i.e. they’re uniquely good at some activity) but not purposes. This is the upshot of Darwin’s theory of natural selection: it removes the need to inelegantly postulate a divine designer by providing a mechanism by which complexity can arise out of simplicity through a series of incremental changes.
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