Defending science from the conservatives

Reinventing Darwin — The Great Evolutionary Debate
By Niles Eldredge
Weidenfeld and Nicolson, 1995
Reviewed by Adam Hanieh The writings of evolutionary biologist and palaeontologist Stephen Jay Gould have an enormously popular following. So it was with some excitement that I stumbled across a book by Niles Eldredge, one of Gould's main collaborators. Reinventing Darwin is a survey of recent debates concerning Darwin's theory of evolution and a critique of views held by conservative academics. Eldredge's major target is Richard Dawkins, scientist and author of the Selfish Gene and The Blind Watchmaker. Put simply, Dawkins argues that the whole process of evolution can be reduced to genes attempting to maximise their replication in successive generations. Hence, human bodies are merely machines to house, feed and protect these "selfish" genes. Eldredge points out that Dawkins presents a mechanistic and reductionist view of science. As well as at a genetic level, organisms exist in local populations within ecosystems. They also exist at a species level, class level (such as mammals), phylum level (invertebrate or vertebrate) and other higher order biological groups. Each of these levels cannot be reduced simply to the level below it and ultimately the genetic level. The whole is more than just the sum of its individual parts. Biological species are defined as groups of organisms which can reproduce with each other. Dawkins and Eldredge have different explanations for how species come into existence. Dawkins and his followers argue that organisms erect reproductive barriers between themselves to adapt more closely to the requirements of their local environment without the dilution of their gene pool through mating with different organisms. Thus, competitive reproduction explains the existence of species. But Eldredge says species exist because of differences that arise naturally in the reproductive systems of isolated communities of species. A single species may become split into different local populations that are isolated from each other. As the isolated populations continue to evolve they reach a point where they no longer recognise each other as potential mates and they become different species. Eldredge goes on to point out that an ecosystem is similarly not reducible to gene competition. Ecosystems are composed of many different populations of organisms that interact with one another. The day to day interaction between organisms in an ecosystem, whether competitive, mutualistic or neutral, determines the nature of the ecosystem. Each organism displays particular behavioural and anatomical adaptations to help it better meet its economic ("economic" in the sense it seeks resources to survive) and reproductive needs. But the laws of motion for this economic system cannot merely be reduced to reproductive needs, writes Eldredge. Another important discussion in Eldredge's book concerns the rate at which evolution occurs. Darwin's original theory of evolution proposed a slow, gradualist change in species as they adapted to meet the demands of changing environment. At the time, this was a revolutionary view because it demonstrated clearly that continuous change was a fundamental feature of the physical world. It also showed that all organisms were related to each other and that the evolution of the human species could be explained scientifically. However, Eldredge and Gould believe that Darwin's view of a slow and gradual evolution is wrong. The fossil record demonstrates that most species remain remarkably similar over long periods of time and then undergo rapid bursts of evolutionary change ("rapid" in palaeontology can mean millions of years). Gould and Eldredge have termed this view of evolution as "punctuated equilibrium". Up until recent times scientists have claimed that gaps in the fossil record were the result of lack of discoveries but recent evidence indicates that these mark the periods where change has taken place in rapid bursts. The process by which species form tends to be closely related to periods of rapid adaptive change. Eldredge suggests that this is due to "species sorting". If a population of organisms forms a new fledgling species that is very similar to the old species then it is likely to be squeezed out of the ecosystem by the more populous parent species and become extinct. However, if there is a large difference in the adaptations of the new species then it may be able to acquire its own ecological niche and continue to survive. The "punctuated equilibrium" model of evolution conforms with Karl Marx's idea of quantitative and qualitative change so it is not surprising that Eldredge and Gould have been accused of "Marxist brainwashing" by the conservative British scientific establishment. Eldredge distances himself from Marxist philosophy but does not elaborate any alternative philosophical framework.