Pangenesis

Pangenesis was Charles Darwin's hypothetical mechanism for heredity. He presented this 'provisional hypothesis' in his 1868 work The Variation of Animals and Plants under Domestication and felt that it brought 'together a multitude of facts which are at present left disconnected by any efficient cause'. The etymology of the word comes from the Greek words pan (a prefix meaning "whole", "encompassing") and genesis ("birth") or genos ("origin"). The hypothesis was eventually replaced by Mendel's laws of inheritance.

The pangenesis theory, similar to Hippocrates's views on the topic, imply that the whole of parental organisms participate in heredity (thus the prefix pan) while adapting to cell theory. Much of Darwin's model was speculatively based on inheritance of tiny heredity particles he called gemmules that could be transmitted from parent to offspring. Darwin emphasized that only cells could regenerate new tissues or generate new organisms. He posited that atomic sized gemmules formed by cells would diffuse and aggregate in the reproductive organs.

The hypothesis of pangenesis was developed by the ancient Greek philosophers such as Hippocrates and Democritus. Darwin wrote that Hippocrates' pangenesis was "almost identical with mine—merely a change of terms—and an application of them to classes of facts necessarily unknown to the old philosopher."

Historian of science Conway Zirkle has noted:

The hypothesis of pangenesis is as old as the belief in the inheritance of acquired characters. It was endorsed by Hippocrates, Democritus, Galen (?), Clement of Alexandria, Lactantius, St. Isidore of Seville, Bartholomeus Anglicus, St. Albert the Great, St. Thomas of Aquinas, Peter of Crescentius (?), Paracelsus, Jerome Cardan, Levinus Lemnius, Venette, John Ray, Buffon, Bonnet, Maupertius, von Haller and Herbert Spencer.

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