Heredity, race, and society.

  • Dunn, L. C. (Leslie Clarence), 1893-1974.
Date:
1947
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Heredity, race, and society. Source: Wellcome Collection.

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    acquired traits are inherited. He even invented what he himself called a provisional hypothesis of pangenesis to visualize how such inheritance might take place. Ac cording to this hypothesis, every part of the body pre pares a kind of diminutive copy of itself, which he called a pangene. These pangenes are transported by blood to the sex glands, where they unite to form the sex cells. A body part which has acquired a new char acter, say an arm the muscles of which have bee ft strengthened by exercise, will bud off an altered pai > gene, and this pangene will produce a modified o r gan in the progeny. \ Darwin knew that his hypothesis of pangenesis was just a guess; this is why he stressed its provisional char acter. But it fulfilled the most important function of any scientific hypothesis: it stimulated a great amount of research and experimentation. For at least thirty years, many biologists, among whom the names of Weis mann and Galton should be mentioned most promi nently, made studies on plants and animals to see whether acquired characters are ever inherited. The number of believers in this contingency dwindled stead ily, because the outcome of the experiments on inheri tance of acquired characters was so uniformly negative. The rediscovery of Mendel's laws and the develop ment of genetics in the current century have produced a much better understanding of the mechanism of he redity than was available in Darwin's and Weismann's day. In the light of this understanding we can clearly see why acquired characters are not inherited. This is because heredity is transmitted through genes and not through blood mixtures (see Chapter 3). Genes arise from each other by division, they are not made in the various organs of the body as pangenes and not trans ported into the reproductive parts and into the sex cells. The genes appear to be chemical molecules which repro duce themselves from the environment, from food. The development of the body is ultimately a by-product of gene reproduction, and not vice versa.