Darwinism, Modern

The Reconciliation of Mendelism and Darwinism

Soon after the publication of On the Origin of Species, the Achilles heel of the whole theory of evolution via natural selection was recognized in an inheritance theory used by Darwin. Darwin worked with the blended-inheritance theory commonly accepted by his contemporaries, which, however, logically undermines the very nature of the evolutionary mechanism as suggested by Darwin, an accumulation of a small inherited adaptive changes through a long time. If inheritance is blended, any accumulation of inherited variations, which is a key element in the gradual building of complex adaptive structures, is impossible. For if heredity is of a blending type, any new variation is halved in every generation, and in fact it disappears very soon. Darwin tried to answer the problem by his own ad hoc theory of heredity (calledpangenesis), a totally speculative one. He flirted with his own version of the inheritance of acquired characteristics (despite the fact that he was strongly critical of Lamarckian theory of evolution), but he never was happy with it. Paradoxically, at the same time, the right answer was already there—in Gregor Mendel's theory of inheritance. Mendel came up with the idea of hereditary “atoms” (he called them “factors”), which cannot blend, but can only combine in a particular rations. Mendel's work was published in 1865, but unfortunately it remained unknown (although not inaccessible to Darwin, as well as to almost all his contemporaries)until it was rediscovered two decades after Darwin's (1882)and Mendel's (1884) deaths at the beginning of 20th century.

German biologist August Weismann (1834–1914) is now known as a forerunner of neo-Darwinism, since he recognized that the Darwinian mechanism of evolution can work perfectly without any kind of Lamarckian inheritance of acquired characteristics, and all it needs is a generation of random changes in hereditary material and selection of those individuals who carry not the best possible adaptations, but better than their competitors.

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