Blackwell Publishing

The rise of evolutionary biology - What was the impact of Mendel's theory of inheritance?


The modern synthesis

By the second decade of the century, research on Mendelian genetics had already become a major enterprise. Within the theory of evolution, the main problem was to reconcile the atomistic Mendelian theory of genetics with the fact that real populations show continuous variation.

This reconciliation was achieved in many stages:

• In 1918 R. A. Fisher demonstrated there that the continuous variation in real populations could be derived from Mendelian principles.

• The next step was to show that natural selection could operate with Mendelian genetics. The theoretical work was mainly done, independently, by R. A. Fisher, J. B. S Haldane, and Sewall Wright. Their synthesis of Darwin's theory of natural selection with the Mendelian theory of heredity established what is known as neo-Darwinism, or the modern synthesis. The old dispute between Mendelians and Darwinians was ended. Darwin's theory now possessed what it had lacked for half a century: a firm foundation in a well tested theory of heredity.

• The reconciliation between Mendelism and Darwinism soon inspired new genetical research in the field and laboratory, such as investigations of evolution in populations of fruitflies and studies of selection in natural populations, mainly of moths.

Helena Cronin describes the modern synthesis.

The image opposite is of Ronald Aylmer Fisher (1890 - 1962) taken in 1912.

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