Abstract
For the past 120 years, the Weismann barrier and associated germ plasm theory of heredity have been a doctrine that has impacted evolutionary biology and our concepts of inheritance through the germline. Although August Weismann in his 1872 book was correct that the sperm and egg were the only cells to transmit molecular information to the subsequent generation, the concept that somatic cells do not impact the germline (i.e., the Weismann barrier) is incorrect. However, the doctrine or dogma of the Weismann barrier still influences many scientific fields and topics. The discovery of epigenetics, and more recently environmentally induced epigenetic transgenerational inheritance of phenotypic variation and pathology, have had significant impacts on evolution theory and medicine today. Environmental epigenetics and the concept of epigenetic transgenerational inheritance refute aspects of the Weismann barrier and require a re-evaluation of both inheritance theory and evolution theory.
Highlights
August Weismann was an influential biologist of the late 1800s who helped formulate thoughts on heredity and evolution, laying some of the foundation for our current understanding of mechanisms of inheritance
He proposed the idea of ‘the continuity of the germ line’; the idea that germ cells contain all the necessary information to form all the different cells of the generation, and that this germ plasm information is replicated and kept isolated in the germ line cells as it is passed from generation to generation (Table 1)
Germ cells, when they form embryos, can direct the formation of the somatic cells that make up the rest of an organism, but somatic cells do not pass heritable information to germ plasm
Summary
August Weismann was an influential biologist of the late 1800s who helped formulate thoughts on heredity and evolution, laying some of the foundation for our current understanding of mechanisms of inheritance. Germ cells, when they form embryos, can direct the formation of the somatic cells that make up the rest of an organism, but somatic cells do not pass heritable information to germ plasm This last point came to be known as the Weismann barrier or Weismann doctrine [2]. Weismann’s theories on germ plasm were presented at a time when the ideas of Darwin and Lamarck were being vigorously debated Both Darwin [3] and Lamarck [4] had proposed the idea that acquired characteristics in an organism could be inherited. Weismann’s ideas were in direct opposition to this, and the experimental evidence of the time seemed to support the idea that somatic cells did not pass to or influence the heritable information in germ cells [5]. A re-evaluation of the Weismann barrier can affect how we think about environmental research, disease etiology, and neo-Darwinian evolution theory
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