Hugo de Vries Biography

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World of Genetics on Hugo de Vries

Hugo de Vries was a Dutch botanist famous for his work in genetics and evolution. He was one of three biologists who helped rediscover Mendel's laws of heredity in 1900. De Vries later became famous for his now-discredited theory that evolution proceeds by rapid mutations. Nonetheless, his work provided an important impetus to new research in the rapidly developing field of genetics in the early twentieth century.

De Vries graduated from the University of Leyden in 1870 with a medical degree. Thereafter he turned his attention to botany, which he began teaching at the University of Amsterdam in the 1870s. He became full professor there in 1881 and continued teaching there until his retirement in 1918.

In 1889, De Vries published a theory of heredity that modified the English biologist Charles Darwin's theory of pangenesis. De Vries agreed with Darwin that heredity was based on particles in the cell, but he believed these particles, which he called pangenes, could not be transferred from cell to cell. De Vries, therefore, called his theory intracellular pangenesis.

The driving force behind De Vries's interest in heredity was his desire to explain how evolution occurs. He surmised that evolution must involve new pangenes being introduced into a species, so he began conducting experiments to try to discover the mechanisms of hereditary variation. In the 1890s he produced hybrids of several plant species with different traits. For example, he crossed a hairy species with a related smooth species, and found that the first generation were all hairy, but the second generation had 392 hairy and 144 smooth individuals, which is approximately a three to one ratio.

After compiling his data on hybridization, De Vries reread Austrian botanist Gregor Mendel's classic paper on plant heredity, which at that time was relatively obscure. De Vries claimed that he rediscovered the Mendelian laws of heredity before rereading Mendel, but many historians are skeptical of this. Mendel's paper was likely a key factor in helping De Vries interpret his own data. In any case, his experiments-like Mendel's-demonstrated that plants inherit traits in pairs of discrete units (now called genes) that segregate before being passed on to the next generation.

After rediscovering Mendelian laws, De Vries continued research with plants to determine how new traits originate. He recognized that Mendelian laws did not answer this question at all. De Vries was also uncertain about how far Mendelian laws could be applied; later he thought that only a minority of traits were inherited in Mendelian fashion. In hybridization experiments with the evening primrose he noticed that occasionally certain traits suddenly appeared in some individuals without any clear antecedent. De Vries used this evidence to formulate his famous mutation theory, which he published in 1900-1903. He believed that evolution was driven by large-scale mutations, i.e., the sudden emergence of new characteristics that become hereditary. He thought that new species or at least subspecies could be formed quickly through these mutations. De Vries considered his theory an alternative to Darwin's theory of natural selection. His mutation theory also set him in opposition to the German zoologist August Weismann's (1834-1914) theory of heredity, as well as the biometrics school of the English scientists Francis Galton (1822-1911) and Karl Pearson (1857-1936), which emphasized small variations.

Later, scientists demonstrated that the mutations De Vries observed were not really introducing new genetic material into organisms at all, as De Vries thought they were. Rather they were merely manifesting latent hereditary traits. Thus the mutations De Vries observed did not provide raw material for significant evolutionary change.

De Vries's mutation theory did stimulate others, such as the American geneticist T. H. Morgan (1866-1945), to conduct experiments on genetic variability. Morhan's idea about mutations later became incorporated into evolutionary theory in the neo-Darwinian synthesis, but only after undergoing radical revisions. Most biologists today reject the idea of rapid mutations, believing instead that evolutionary variations are produced by micromutations that accumulate gradually.