DARWIN, CHARLES

(1809–1882)

The naturalist Charles Robert Darwin expounded the first successful theory of evolution based on the processes of natural selection in botanical and animal populations. The son of a physician and the grandson of a well-known polymath, Erasmus Darwin, Charles Darwin drifted from medicine at Edinburgh to preparation for a career in the Church of England at Cambridge while enjoying country pursuits such as hunting, shooting, and specimen collection throughout his young adulthood. Recognition of his skills as a naturalist first came in the form of an offer to undertake the geological, zoological, and botanical side of the official naval survey of the South American coast carried out by the HMS Beagle from 1831 to 1836. Upon his return, private wealth enabled Darwin to remain an independent scientist for the rest of his life.

In the course of trying to make sense of his observations, Darwin hit upon the main ideas that were later to constitute the theory of natural selection. Reading the economist T. R. Malthus's Essay on Population in 1838 provided an essential step in that process. Darwin was familiar with competition for survival in the animal kingdom, but the quasi-mathematical form of Malthus's theory of the potential force exerted by population growth on resources in unchecked populations proved fruitful. It revealed that there was a persistent process at work by which individual members of any species that possessed slight advantages in the struggle for survival would succeed while others either failed to breed or went extinct. Lack of room and nourishment sets up a competition in which the better adapted have a greater chance of breeding and thus of passing on the original variation. Publication of Darwin's findings was much delayed: The Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life was not published until 1859 after Darwin learned that the scientist Alfred Russel Wallace (1823–1913), who had also been influenced by reading Malthus, was about to publish a similar theory.

The study of animal populations in terms of why they fail to show the exponential properties suggested by Malthus's geometric ratio, the interaction between birth rates and death rates, and the effect of density and territoriality in constraining fluctuations in population size followed in the wake of the interest shown in human populations. For Darwin and Wallace that interest centered on positive checks and their implications for natural selection.

Detailed studies of the principles of population interaction and competition were delayed until the twentieth century. David Lack, for example, showed that birds exercise reproductive control through natural selection. Clutch size converges on the "efficient" solution: It corresponds to the largest number of young for which the parents can on average find sufficient food.

Malthus, who was attacked for stressing the aspects of behavior that humankind shares with animals, became important to biology precisely because of this fact. Malthus's habits as an observer, balancing speculation with detailed observation, are similar to those involved in natural history. Any reader with the experience of Darwin and Wallace would recognize the same mentality, procedures, and need to fill the gaps in knowledge created by the absence of scope for controlled experimentation with natural populations. Ultimate and proximate causes need to be separated, but that can be done only with great difficulty. Migration to other regions also causes similar problems when one tries to draw inferences. This led to Darwin's problem in proving that what could be observed as a result of artificial selection was also true of natural selection. Because of the current availability of accurate human population statistics, Darwin's observations continue to offer a benchmark for noting differences in animal population behavior.

Darwin's theory, having acknowledged its debts to the human or social sciences, exerted a reciprocal influence on the study of human populations. It did this not so much through questions involving quantities, Malthus's sole concern, but through questions affecting qualitative changes in human populations as judged by intelligence or other properties deemed to be heritable. This question was first addressed by Darwin's cousin, Francis Galton (1822–1911), whose studies of the inheritance of intelligence, though first undertaken without a knowledge of genetic transmission mechanisms, launched the field known as eugenics. Darwin appropriated Galton's ideas on the effect of inheritance in his Descent of Man (1871), giving his personal blessing to one version of a doctrine already in circulation, social Darwinism, or what would later be called sociobiology.

See also: Animal Ecology; Biology, Population; Eugenics; Evolutionary Demography; Galton, Francis; Malthus, Thomas Robert; Sociobiology.

BIBLIOGRAPHY

Barlow, Nora, ed. 1969. The Autobiography of Charles Darwin, 1809–1882. New York: Norton Library.

Bowler, Peter J. 1976. "Malthus, Darwin, and the Concept of Struggle." Journal of the History of Ideas 37: 631–650.

Browne, Janet. 1995. Charles Darwin; Voyaging. London: Jonathan Cape.

Darwin, Charles. 1985 (1859). The Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. London: Penguin.

——. 1998 (1871). The Descent of Man and Selection in Relation to Sex. Great Minds Series. Amherst, NY: Prometheus Books.

Galton, Francis. 1972 (1869). Hereditary Genius; An Inquiry into its Laws and Consequences. Gloucester, MA: Peter Smith.

Lack, David. 1952. The Natural Regulation of Animal Numbers. Oxford: Oxford University Press.

DONALD WINCH