In this five-part series, Jonathan Miller returns to his roots in medicine and tells the story of how we came to understand reproduction & heredity. Disposing with the idea of an external, perhaps even supernatural, vitalising force, he describes how we have arrived at the picture of ourselves and all organisms as Self-Made Things.
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This week, Jonathan Miller describes the research that eventually led us to identify the gene as the key agent of inheritance.
One of the most important figures in this search was a nineteenth century Augustinian monk called Gregor Mendel. Robert Olby tells Jonathan about Mendel's hybridisation experiments which showed for the first time that plants inherited characteristics according to a mathematical pattern. Mendel recognised that characteristics could be recessive or dominant, so that traits could 'disappear' from one generation and 'reappear' in the next.
In 1859, Charles Darwin published 'On the Origin of Species' which laid out the theory of evolution by natural selection. But as Enrico Coen says, Darwin had little idea about the actual physical processes of inheritance. He thought that hereditary particles representing each part of the body - he called them gemules - were somehow collected together and passed on to the next generation. The fact that circumcised males managed to pass foreskins on to their male offspring was something Darwin was unable to explain.
The ideas of Darwin 's contemporary, the German biologist August Weissmann, were far more convincing. Richard Dawkins is full of admiration for Weismann's concept of a river of hereditary particles, insulated from environmental influences, flowing through the generations and determining the characteristics of individual species.
But as Evelyn Fox Keller argues, it wasn't until the beginning of the twentieth century that scientists began to realise that the key to inheritance lay as much in the mechanisms that activate the genes, as in the genes themselves.