Evolving Thoughts

Evolution, culture, philosophy and chocolate! John Wilkins' continuing struggle to come to terms with impermanence... "Humanus sum, nihil humanum a me alienum puto" - Terence

Monday, June 20, 2005

The not-so-Great Chain

This item in Nature was brought to my attention by a post on sci.bio.evolution, which I had missed when it was published four weeks ago because I'm getting sloppy in my reading (well, I'm reading stuff published in the middle ages through to the 18th century, so cut me some slack).

It is a short comment by Stephen Nee on the tendency of evolutionary thinkers to reinvent or reassert the Great Chain of Being, a view of life first substantially and clearly expressed by historian of ideas, E. O. Lovejoy in 1936. But it goes back to Aristotle and is found throughout the middle ages until now. Basically it is the idea that there is a continuous scale of organisation from very simple living things to us.

But the Great Chain is more than a hangover; it is a durable idea. It infects anthropology, cognitive studies, and philosophy as well as biology, and it was inserted into evolutionary traditions when Lamarck borrowed the scale from Bonnet in the early years of the 19th century and turned it on its side. No longer did the ladder range from bottom to top (approaching God in the process); now it ranged from early to late, with later being better in some way.

Darwinian evolution, however, is not a Great Chain. Later is just... later. Of course Darwin himself got a bit confused about this from time to time, but the message that Darwinian evolution was not necessarily progressive, and that humans are not the single most spectacular opus of Nature ever was clear, and offensive! Rejecting this implication of evolution, in cultural evolution as well as biological evolution, became a cottage industry, involving reinterpretations of Schopenhauer, Hegel, and Kant, as well as devising sometimes mystical evolutionary accounts (Teilhard or Bergson), or special cases for culture (Gould comes to mind, but there are many others, such as Rescher).

Nobody seemed too happy to accept that humans were just another organism, special in its own way as every species is, not not special in a unique style. Nor did they seem happy to accept that history no more than biology is not linear and progressive. Still it persists. Maynard Smith and Szathmary, as noted in the article, treat the seven stages of evolution from microbe to us (at any rate the ones they deem significant) as linear and in a way predetermined.

I sometimes suspect that scientists are so keen to see the Great Chain in biology because it underpins their belief that science is likewise progressive. But science is not progressive in any simple linear sense at all - theories go dormant to be revived two thousand years later (atomism, material heredity), or they die because they are dead ends (phlogiston, ether), or bad results don't get published, leaving the implication that science progresses (Pasteur published only 10% of his results on heterogeny - spontaneous generation of modern organisms - discarding the "wrong" ones. It caused a scandal in France when this was published). The impression that science or biology progresses can only be maintained by ignoring all the "wrong" events, processes and tendencies.

So, boys and girls, I strongly recommend you all purge yourselves of the belief that it's getting better all the time. Sometimes it does, and sometimes it doesn't. And sometimes being us is no real improvement by any measure.

Lovejoy, A. O. (1936). The great chain chain of being: a study of the history of an idea.
Cambridge, Mass., Harvard University Press.