Thursday, September 13, 2007

Stephen Jay Gould, and random mutation

"Conceptual locks are far more powerful than factual lacks as barriers to scientific understanding" - S.J.G.

Stephen Jay Gould was a prominent evolutionary biologist, whose significant achievements included the concept of punctuated equilibrium (previously discussed here), and a welter of lucid writing that seeped into popular consciousness more than any other writer in his discipline since Darwin.

He died in 2002, but not before publishing a series of books based on over 25 years worth of essays for the magazine Natural History.

I'm currently journeying through his collection Eight Little Piggies (Jonathan Cape, 1993). His writing style is clear but erudite. The essays are interesting and easy to follow. But there is a trap that I believe is common to most discourse on evolution, both at a lay and a professional level: it is so very easy to misconstrue concepts. They are often subtle, writ on different scales to our own (in terms of both time and species). On the one hand, there are many fallacies built around the key phrases that sum up the popular conceptualisation of evolution, such as "survival of the fittest" and "natural selection". On the other hand, there are so many disputes between the professionals that consensus-building seems to take substantially longer than in harder physics disciplines such as cosmology or subatomic theory. This is because theory is necessarily built on small populations of fossils that each new discovery has potential to cause paradigm shift.

And interlaced throughout is the burden of anthropocentricism, the framework that lures people into thinking too much in the context of the here and now species.

And so Gould's essays are sometimes straightforward in their ramifications, but often require a re-read to catch the "correct" nuance and avoid the hidden missteps and solipsisms.

So I go carefully. And start with some clear concepts picked up from this book.

The first essay, Unenchanted Evening, follows the course of a species of snail (Gould's original academic focus) on the French Polynesian island Moorea. He traced the meticulous work of Henry Crampton last century, who made incredibly detailed studies of the Partula.

Gould illustrated how the body of measurement, description, and sampling was valuable not just as a comprehensive snapshot, but an excellent baseline for future study of changes in that species.
Unfortunately, it was driven to extinction. First, another species of snail was accidentally introduced that drove Partula to the brink, then a third species was intentionally introduced to control the second - but which instead clinched the fate of the Partula.

Biological control is fraught, absolutely. As any Queenslander ever plagued by cane toads will tell you. Introduced to control a sugar cane pest (which they never did), they are toxic and gradually spreading their way across the whole of Australia.

Yet there was a meaningful conceptual outcome of Compton's work. The island of Moorea is based on a volcano, and its topography is such that there are ridges and valleys all around the island. The Partula snail was partial to the valleys but not the ridges, so the population consisted of a series of sub-populations that were to a great extent isolated from each other. And each of those populations was physically different in form and colour. The question was whether those differences were due to unidentified differences in those niche environments, or random differences.

Crampton interpreted the differences as being due to three major causes: isolation, mutation, and natural selection. Isolation simply created the conditions for independent populations. Crampton saw natural selection as mainly negative, simply in terms of unhelpful mutations not surviving. And so the differences were due to random mutation.

"the role of the environment is to set the limits to the habitable areas or to bring about the elimination of individuals whose qualities are otherwise determined, that is, by congenital factors".

This has parallels with Darwin's Galapagos finches, with the difference here that there is no firm necessity for the sub-population differentiations.

Gould rated Crampton's labours and conclusions very highly.

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