Events since 1959

The molecular revolution that began with the discovery of the structure of DNA in the 1950s had a profound effect on evolutionary biology. Not only have molecular mechanisms that bias the transmission of heritable information to the next mechanism been discovered, but, in addition, the mere fact that so much has been learned about the structure and function of DNA and RNA has reintensified focus on the gene.

Thus one major movement that began as early as the 1960s was to recast Darwinian selection more expressly in terms of genes— a movement perhaps best exemplified by the notion of the "selfish gene" promulgated by British biologist Richard Dawkins. Dawkins and colleagues developed a picture of the biological world centered around the importance of transmission of genetic information to the next generation: even genes compete with one another to be transmitted to the next generation.

One aspect of this line of research has been the development of sociobiology and its even more recent offshoot, human "evolutionary psychology." One problem plaguing Darwin from the very beginning was the existence of so-called altruism, whereby, instead of competing with one another for food and other resources, including mates, organisms within many species actually are observed to cooperate. British biologist W. D. Hamilton, in the 1960s, showed convincingly that the degree to which organisms cooperate is proportional to the number of genes that they share; close relatives cooperate, because cooperation in this case fosters the transmission of each individual's genes. From these critical observations, socio-biology (named and first thoroughly discussed by American biologist Edward O. Wilson in the 1970s) was developed—an evolutionary biological account of social systems from the perspective essentially of the gene.

On the other hand, paleontologists were making further discoveries on their own. In the early 1970s, for example, paleontologists Niles Eldredge and Stephen Jay Gould pointed to the long-neglected phenomenon of stasis—the tendency of most species as seen in the fossil record to remain pretty much unchanged, often for millions of years, in stark contrast to the standard expectation, going back to Darwin, that species will almost inevitably change slowly and gradually through geological time. In their notion of punctuated equilibria, Eldredge and Gould combined their observations on stasis with the Mayr/Dobzhansky theory of speciation.

Still further work in paleontology has revealed the importance of mass extinctions in evolution. The net effect has been a re-emphasis on the importance of the physical environment in causing extinctions and in triggering renewed bursts of evolution as an aftermath to extinction. Turnover pulses, a term coined by paleontologist Elisabeth S. Vrba, are episodes of sudden extinction of many species within a regional ecosystem, followed by bursts of speciation—all triggered by pronounced regional environmental change leading to disruption of entire biomes. Such turnovers are an essential ingredient of the Sloshing Bucket theory of evolution.

Much remains to be done; science never rests, and no answers are final. Although biologists agree that life has evolved, they still disagree about some of the details of exactly how evolution actually occurs. Creationists point to this disagreement as evidence that evolutionary biology is not true science—as if chemists and physicists did not openly and actively disagree with one another! Much progress has been made in understanding how the evolutionary process works. The task now, for even further progress, is to integrate the gene-centered view with the environmentally oriented views set forth above. There still is plenty to be done in evolutionary biology!

—Niles Eldredge

See also: Adaptation; Darwin, Charles; Evolutionary Biodiversity; Evolutionary Genetics; Human Evolution; Linnaean Hierarchy; Natural Selection; Paleontology; Punctuated Equilibria; Speciation; Species; Systematics; Wallace, Alfred Russell

Bibliography

Darwin, Charles R. 1859. On the Origin of Species. London: John Murray; Dawkins, Richard. 1976. The Selfish Gene. New York: Oxford University Press; Eldredge, Niles. 1989. Macroevolutionary Dynamics: Species, Niches and Adaptive Peaks. New York: McGraw-Hill; Eldredge, Niles. 1999. The Pattern of Evolution. New York: W. H. Freeman; Futuyma, Douglas J. 1997. Evolutionary Biology. Sunderland, MA: Sinauer; Maynard Smith, John. 1993. The Theory of Evolution. Cambridge: Cambridge University Press; Mayr, Ernst. 2001. What Evolution Is. New York: Basic; Williams, George C. 1966. Adaptation and Natural Selection. Princeton: Princeton University Press; Wilson, Edward O. 1975. Sociobiology. Cambridge: Harvard University Press.

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