Part One
THE EVOLUTIONARY IDEA
The universe is changing in time, and it has evolved from something simpler to something more complex. That is the lesson to be learned from recent advances in evolutionary theory; the emergence of order has colored biology since Darwin and twentieth-century cosmology alike.In Darwin's day, the exact manner of the inheritance of characteristics was not known; Darwin himself believed that certain characteristics were acquired by an organism as a result of environmental change and could be passed to the organism's offspring, an idea popularized by the French naturalist Jean- Baptiste Lamarck. In 1900, the work done by Mendel some fifty years earlier was brought to light, and the gene, though its exact nature was unknown at the time, became a player in "the modern synthesis" of Mendel and Darwin. This synthesis, which reconciled genetics per se with Darwin's vision of natural selection, was carried out in the early 1930s by R.A. Fisher, J.B.S. Haldane, and Sewall Wright, and augmented a few years later by the work of the paleontologist George Gaylord Simpson, the biologist Ernst Mayr, and the geneticist Theodosius Dobzhansky, who expanded on this neo-Darwinian paradigm. Nevertheless, there is still discord in the ranks of evolutionary biologists. The principal debates are concerned with the mechanism of speciation; whether natural selection operates at the level of the gene, the organism, or the species, or all three; and also with the relative importance of other factors, such as natural catastrophes.
Among the evolutionary biologists, George C. Williams is the senior figure in the book. People outside the field who take an interest in evolution are much more likely to think of Stephen Jay Gould or the British evolutionary biologist Richard Dawkins; few laypeople have heard of Williams. Yet nearly all evolutionary biologists, even those who do not agree with him, admire him. Williams was the first to emphasize that it was the gene on which natural selection acted. In this regard, he precedes Richard Dawkins, with whom he shares a great many ideas, and he is in a different camp from Stephen Jay Gould, who has a hierarchical theory of selection processes, of which the gene is only one level. Williams' book Adaptation and Natural Selection, published in 1966, was a treatise on what has become known as ultra-Darwinism. In recent work, Williams describes the gene as having a "codical" as well as a physical character — that is, he views the gene as a package of information, not an object.
Stephen Jay Gould is known among evolutionary biologists for three things: "punctuated equilibria," a theory he developed with Niles Eldredge which says that one species does not gradually turn into another but that species emerge suddenly; resuscitation of the study of relationships between embryology and evolution, as expressed in his landmark book Ontology and Phylogeny; and a famous paper, written with the population geneticist Richard Lewontin, titled "The Spandrels of San Marco and the Panglossian Paradigm; A Critique of the Adaptationist Program." He is also widely read. His books (Wonderful Life, Bully for Brontosaurus) are on best-seller lists around the world.
Paleontologists study the fossil record. The questions they face concern such things as long-term patterns in the history of life, and the extinction of species over millions of years. In this regard, Gould carries forward the attitude of many paleontologists towards evolutionary biology: namely, skepticism regarding the domains and the powers of natural selection. He is often critical of the ultra-Darwinian views of mainstream evolutionists such as Williams and Dawkins.
Gould is attempting to weave together three themes in order to expand the current Darwinian model: the first is the hierarchical theory of natural selection; the second notes the limitations on evolution imposed by biological constraints on adaptation; the third concerns catastrophic events in geologic time, which can cause mass extinctions. Because Gould is a prolific and gifted popularizer, the educated public, at least in America, assumes that his approach to evolutionary biology is the mainstream position. Not so; he is a critic of the mainstream, which is dominated by Williams, the English evolutionary biologist John Maynard Smith, and Dawkins.
Richard Dawkins is considered by his peers to be the ultimate ultra-Darwinist. He is also a gifted writer, who is known for his popularization of Darwinian ideas as well as for original thinking on evolutionary theory. He has invented telling metaphors that illuminate the Darwinian debate: His book The Selfish Gene argues that genes — molecules of DNA — are the fundamental units of natural selection, the "replicators." Organisms, including ourselves, are "vehicles," the packaging for "replicators." The success or failure of replicators is based on their ability to build successful vehicles. There is a complementarity in the relationship: vehicles propagate their replicators, not themselves; replicators make vehicles. In The Extended Phenotype, he goes beyond the body to the family, the social group, the architecture, the environment that animals create, and sees these as part of the phenotype — the embodiment of the genes. He also takes a Darwinian view of culture, exemplified in his invention of the "meme," the unit of cultural inheritance; memes are essentially ideas, and they, too, are operated on by natural selection.
Brian Goodwin looks on biology as an exact science, and sees the "new biology" less as a historical science than as an enterprise similar to physics in its emphasis on principles of order. He represents the structuralist approach, which resonates with the Scottish zoologist D'Arcy Thompson's idea that evolutionary variation is constrained by structural laws; not all forms are possible. Goodwin is passionately opposed to the reductionist view of the ultra-Darwinians, and much more comfortable with the complexity ideas of Stuart Kauffman and with Francisco Varela's holistic approach to biology.
Steve Jones is a highly regarded geneticist and snail biologist. He is interested in why so much diversity exists in animals and plants: why no two individuals are alike. Surely, it can be argued, natural selection should instead inevitably lead to the evolution of one perfect form for each species. He works on the striking variety of shell color and banding patterns in the land snail Cepaea nemoralis. Cepaea has been seen as an archetype of diversity since the nineteenth century. In the 1950s, the English biologists Arthur Cain and Phillip Sheppard argued that such apparently trivial differences were under the action of natural selection (in this case because birds would attack the conspicuous forms). Jones finds that climate is also involved and — most important — that differences in microclimate on the scale of a few inches can alter the behavior and survival of snails of different pattern. Ecologically complex habitats hence foster genetic diversity. Jones has been writing and lecturing about science to a general audience for ten years. His most recent book, The Language of the Genes, won the 1994 Science Book Prize.
Niles Eldredge, a paleontologist who is closely associated with Stephen Jay Gould, believes that species are information repositories; the theory of punctuated equilibria provides evidence that species, once they originate, tend to remain stable, while change occurs by rapid events of branching by small populations splitting off from ancestral species. Eldredge is known for his work on the hierarchical structure of biological systems and for his criticisms of the adaptationist program. Since the late 1960s, he and Gould, the "naturalists," have been locked in intellectual debate with George Williams, John Maynard Smith, and Richard Dawkins over such issues as where selection takes place. Eldredge believes that metaphors of competition, while appropriate at the level of reproductive biology, fail as an explanatory principle for large-scale biological systems. He also makes the point that while the ultra-Darwinians consider themselves reductionists, they go down only to the genes-within- populations level, and don't pay much attention to molecular biology.
Biologist Lynn Margulis would extend evolutionary studies nearly four billion years back in time. Her major work has been in cell evolution, in which the great event was the appearance of the eukaryotic, or nucleated, cell — the cell upon which all larger life-forms are based. Nearly thirty years ago, she argued for its symbiotic origin: that it arose by associations of different kinds of bacteria. Her ideas were generally either ignored or ridiculed when she first proposed them; symbiosis in cell evolution is now considered one of the great scientific breakthroughs.
Margulis is also a champion of the Gaia hypothesis, an idea developed in the 1970s by the free lance British atmospheric chemist James E. Lovelock. The Gaia hypothesis states that the atmosphere and surface sediments of the planet Earth form a self- regulating physiological system — Earth's surface is alive. The strong version of the hypothesis, which has been widely criticized by the biological establishment, holds that the earth itself is a self-regulating organism; Margulis subscribes to a weaker version, seeing the planet as an integrated self- regulating ecosystem. She has been criticized for succumbing to what George Williams calls the "God-is good" syndrome, as evidenced by her adoption of metaphors of symbiosis in nature. She is, in turn, an outspoken critic of mainstream evolutionary biologists for what she sees as a failure to adequately consider the importance of chemistry and microbiology in evolution.
Excerpted from The Third Culture: Beyond the Scientific Revolution by John Brockman (Simon & Schuster, 1995) . Copyright © 1995 by John Brockman. All rights reserved.