Purpose in Evolution

I stumbled across renegade philosopher Chris Bateman during Covidtide, and have found him a breath of fresh air in a world where intellectuals rarely say unexpected things. Bateman is difficult to categorize both philosophically and politically, a sure sign of a vivid and independent mind. He always approaches his topics with good will and generosity to his "opponents", and his arguments are lucid and always good food for thought, regardless of whether or not I agree with them.

I have only read one of Bateman's books to date (though I hope to dig into more in the future), namely, The Mythology of Evolution, which I found an invaluable resource to investigating the unspoken assumptions that we all bring to the table with powerful and pervasive "myths" like evolution. Most of the book I found well-argued, and couldn't help but agree with its conclusions, but there was one section that I took small issue with.

The structure of the book involves Bateman identifying, pursuing, and challenging six metaphors that are often taken for granted when scientists and laypeople speak about the process of evolution in living species. Bateman throughout proposes new replacement metaphors which he feels do a better job of communicating the actual features of evolution, without introducing as much accidental baggage as the metaphors commonly in use (or perhaps, introduce better accidental baggage). Frustratingly, I've been unable to locate my copy of the book, and will have to rely on my memory of a particular chapter, rather than on quotes. Luckily, no one is reading this blog.

One of the metaphors that Bateman sets out to unroot is the metaphor of "purpose". That is, since he takes "purpose" to mean "having been designed aforethought by a rational agent with a use in mind", the various body parts and structures of plants, animals, and other living things cannot be said to have purposes, and that we are led astray in understanding living things if we insist on applying this metaphor too closely.

I think this is unfair to the concept of "purpose". I don't think there's a defensible notion of something having a purpose that includes hammers, but not the tails of squirrels. In many ways, the tail of a squirrel is substantially more purposeful than a hammer, as many times more parts need to interact in unfathomably more complex ways to pursue more sophisticated ends (such as balance and warmth). Tying purpose to the historical design plans of a rational mind (I assume Bateman is not counting God in his argument) seems to empty the word "purpose" of a great deal of its actual content. A rough-and-ready approximation I would provide for a more general definition would be something along the lines of "if X occurs always and only in the context of aiding in the performance of Y, then Y is the purpose of X". It is very to the point that the tail of a squirrel does not occur in any other context than on the backside of a squirrel, and wherever that squirrel is functioning in its own distinctive fashion, it uses its tail extremely effectively as a means for a variety of ends. To say that a squirrel's tail has no purpose is only to shroud it in unnecessary mystery.

The fact that various body parts may have multiple purposes is no concern, nor that they could be "discovered" to be useful in new and surprising ways in a novel circumstances. Nor is it a problem that purposes are sometimes misattributed. If a man declares the purpose of the pineal gland to act as the seat of the immaterial soul, the correct response to him is not to say "in fact, the pineal gland, like all body parts, has no intrinsic purpose"—rather, one responds that the pineal gland's purpose is to produce melatonin, which serves a variety of further purposes in the brain.

I am inclined to think that "purpose" is a very general concept, which can have stronger or weaker cases. A rational agent designing something or other surely imbues it with a purpose (at least when the work is done well), but I call this a special case of a larger principle. Intestines have purposes, lives have purposes, waterfalls have purposes (to suddenly decrease the gravitational potential energy of water), and so on. The "strength" or "purity" of these purposes varies, certainly, but to say that purpose, by definition, includes only the works of man is to err in a most anthropocentric way.