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Heredity (the adjective is hereditary) is the transfer of characteristics from parent to offspring, either through their genes or through the social institution called inheritance (for example, a title of nobility is passed from individual to individual according to relevant customs and/or laws).
Biology
In biology, heredity refers to the transfer of biological characteristics from a parent organism to offspring, and is practically a synonym for genetics, as genes are now recognized as the carriers of biological information. In humans, defining which characteristics of a final person are due to heredity and which are due to environmental influences is often controversial especially regarding complex traits such as intelligence and race. (See also the nature versus nurture debate.)
History of heredity in biology
It was apparent to ancient humans that offspring resembled their parents. For example, Genesis 30-46 tells how Jacob and Laban split their sheep into white and speckled varieties so they could distinguish the two to ensure none were later stolen. Although it was clear that traits were hereditary, the precise mechanism of heredity was not clear.The Bible's understanding of heredity was primitive at best. The same passage in Genesis suggests that spotted sheep are produced by rams & ewes mating in front of black & white tree branches.Various hereditary mechanisms were envisaged without being properly tested or quantified. These included blending inheritance and the inheritance of acquired traits. Nevertheless, people were able to develop domestic breeds of animals as well as crops through artificial selection. The inheritance of acquired traits also formed a part of early Lamarckian ideas on evolution.
Charles Darwin proposed a theory of evolution in 1859 and one of its major problems was the lack of an underlying mechanism for heredity. Darwin believed in a mix of blending inheritance and the inheritance of acquired traits (pangenesis). Blending inheritance would lead to uniformity across populations in only a few generations and thus would remove variation from a population on which natural selection could act. This led to Darwin adopting some Lamarckian ideas in later editions of The Origin and his later biological works. Darwin's primary approach to heredity was to outline how it appeared to work (noticing that traits could be inherited which were not expressed explicitly in the parent at the time of reproduction, that certain traits could be sex-linked, etc.) rather than suggesting mechanisms.
Darwin's initial model of heredity was adopted by, and then heavily modified by, his cousin Francis Galton, who laid the framework for the biometric school of heredity. Galton rejected the aspects of Darwin's pangenesis model which relied on acquired traits.
The inheritance of acquired traits was shown to have little basis in the 1880s when August Weismann cut the tails off many generations of mice to find that their offspring did continue to develop tails.
The idea of particulate inheritance of genes can be attributed to the Austrian monk Gregor Mendel who published his work on pea plants in 1865. However, his work was not widely known and was rediscovered in 1901. It was initially assumed the Mendelian inheritance only accounted for large (qualitative) differences, such as those seen by Mendel in his pea plants — and the idea of additive effect of (quantitative) genes was not realised until R.A. Fisher's (1918) paper on The Correlation Between Relatives on the Supposition of Mendelian Inheritance. For the subsequent history of genetics, see history of genetics.
In the 1930s, work by Fisher and others resulted in a combination of Mendelian and biometric schools into the modern synthesis of evolution.
Trofim Lysenko however caused a backlash of what is now called Lysenkoism in the Soviet Union when he emphasised Lamarckian ideas on the inheritance of acquired traits. This movement affected agricultural research and led to food shortages in the 1960s and seriously affected the USSR.
Sociology
The social institution called inheritance. One's bloodline is one's familial ancestry. See also meme.
References
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"Heredity"