15.02.1996

Heresy and orthodoxy

Danny Hammill reviews 'Reinventing Darwin: The Great Evolutionary Debate' by Niles Eldredge, (Weidenfeld and Nicolson, 1995, pp244)

According to a June 1993 Gallup poll, 47% of adult Americans believe that Homo sapiens is a species created by god less than 10,000 years ago. Over the last couple of years we have seen the ascendancy of the religious right, most notably in the shape of the Christian Coalition-backed Pat Buchanan.

Scary, right? Given the rising tide of irrationalism and general hostility to scientific progress, it is always a relief to turn to a passionate defence of scientific rationality and, in particular, the Darwinian world view - which, in the words of its most articulate exponent, Richard Dawkins, “seems to be regarded as fair game for critics with any degree of ignorance” (The Blind Watchmaker, preface). Eldredge’s text will be a useful weapon in the battle against ‘sceptics’ of all hues.

Niles Eldredge is a distinguished paleontologist who in 1972, alongside the even more distinguished Stephen Jay Gould, first outlined the theory of ‘punctuated equilibria’. This scientific paper generated much heat. The editor of Biblical Creation claimed that “the credibility of our religious and scientific position has been greatly strengthened” by the theory, presumably sensing the hand of the creator behind it.

How come? Eldredge and Gould suggested that the apparent existence of ‘gaps’ in the fossil record were a true reflection of what really happened, rather than being the inevitable consequence of an ‘imperfect’ fossil record. In other words, evolution did in some sense go in sudden bursts, punctuating long periods of ‘stasis’, when no evolutionary change took place in a given species. They provocatively, and possibly unwisely, counterposed this jerky and abrupt process of ‘punctuated equilibria’ to so-called ‘phyletic gradualism’ - Darwin’s alleged belief in the constancy of rates of evolution.

Reinventing Darwin is a sustained defence of punctuated equilibria and the importance of stasis in the evolutionary process. This is a major deviation from orthodox neo-Darwinism - or, as Eldredge insists on labelling it, “ultra-Darwinism” - which fundamentally views stasis as just a passive lack of evolution, due to the absence of a driving force. Eldredge seems to be suggesting that there are genetic forces in large populations that actively resist evolutionary change.

Heretical stuff. Also, quite possibly, a fuss about nothing. Dawkins - who articulates “the general ultra-Darwinian perspective” (p195) - accuses Eldredge of confusing gradualism with ‘constant evolutionary speedism’, which was not Darwin’s belief. Also, if we look at fossil ‘gaps’, we are “probably not looking at an evolutionary event at all; we are looking at a migrational event. The arrival of a new species from another geographical area” (original italics, The Blind Watchmaker, p240).

Eldredge reminds us that these titanic polemics are all “attempts to paint a better picture of nature” (p227); they can only ever be approximate. The discovery that the earth is not a perfect sphere but a slightly flattened spheroid did not therefore mean that the flat earth theory was vindicated and Copernicus got it wrong. The same goes for evolutionary discourse.

Danny Hammill