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

Sunday, June 12, 2005

On devolution

I recently received this question in email. I hope the correspondent doesn't mind my posting it anonymously.
I notice from www.dictionary.com that the word "Devolution" is a term in biology which means "degeneration". Is it an antonym of the word "Evolution" (which is the most likely reason why creation "scientists" state tiresome statements like "evolution would argue for improvements all the time")? Or does the word "devolution" touch on stuff that may or may not be related to evolutionary biology?
Traditionally, degeneration meant simply change from the type. There was no indication that this was a loss of information or fitness, but of form. Prior to the 17th century, species were regarded as the result of generation - any change from the species was hence "degeneration".

"Devolution" means something like passing down or imparting (for example, the passing of home rule powers to a territory or subject nation):

1. A passing down or descent through successive stages of time or a process.

2. Transference, as of rights or qualities, to a successor.

3. Delegation of authority or duties to a subordinate or substitute.

4. A transfer of powers from a central government to local units.

5. Biology Degeneration.
From the American Heritage Dictionary (OED is offline right now, for some reason).

Although the dictionaries I have accessed do seem to say that devolution and degeneration mean retrograde (biological) evolution, this is not regarded as a biological term as such. A biological dictionary at biology-online.org gives it as:
A continuing process of degeneration or breaking down, in contrast to evolution.
But the root "volvo" or "volutus" means a rolling-down. So de-volving would involve (sorry) a de-rolling down. That is, a rolling up.

The term evolution originally meant, in a biological context, a rolling out of the generation of an organism. In the context of the debates over generation of the pre-modern period, this meant that development was pre-determined (two theories were the preformationists and the epigenesists - the first that God put all future generations in the first seed of Adam or Eve, and the second that unformed matter was formed by some power to become the mature organism).

The first theories of evolution were a temporalised version for species of evolution of organisms. That is, it meant that evolution (the process we call evolution) was predetermined. Each species was, in effect, formed at the beginning and only later expressed. So if there is a developmental sequence for species, then anything that reverses that sequence is devolution and degeneration.

But Darwin's view of what he called transmutation (only later did he accept "evolution", and then under some pressure, due to the prior usage by Spencer and others) had not implicit direction. Any change was evolution, including reversals. So it is wrong to call evolutionary change devolution unless it is indexed to some important character. For example, the vestigial males of rotifers and other zooplankton, where the male is little more than a sperm donor and lives attached to the female, is degeneration from the ancestral form of a male, but is just evolution.

It has become a commonplace phrase amongst those who object to evolution because they think, wrongly, that all evolutionary change must be an advance in all respects. This is not true except in the very general sense that no variant can be less fit to any great degree than its supplanted competitors. If this means that adult males become degenerate, then so be it - it's still evolution.