Editing Genetic variation (section)

=== Darwin's concept of heritable variation ===
[[Charles Darwin]]'s ideas of heritable variation were shaped by both his own scientific work and the ideas of his contemporaries and predecessors.<ref>{{Cite journal|last=Egerton|first=Frank N.|date=1976|title=Darwin's Early Reading of Lamarck|jstor=230686|journal=Isis|volume=67|issue=3|pages=452–456|doi=10.1086/351636|s2cid=144074540|issn=0021-1753}}</ref> Darwin ascribed heritable variation to many factors, but particularly emphasized environmental forces acting on the body. His theory of inheritance was rooted in the (now disproven) idea of [[Pangenesis|gemmules]] - small, hypothetical particles, which capture the essence of an organism and travel from all over the body to the reproductive organs, from which they are passed to offspring.<ref>{{Cite journal|last=Winther|first=Rasmus G.|date=2000|title=Darwin on Variation and Heredity|jstor=4331610|journal=Journal of the History of Biology|volume=33|issue=3|pages=425–455|doi=10.1023/A:1004834008068|s2cid=55795712|issn=0022-5010}}</ref> Darwin believed that the causal relationship between the environment and the body was so complex that the variation this relationship produced was inherently unpredictable.<ref>{{Cite journal|last=Beatty|first=John|date=2006-12-01|title=Chance Variation: Darwin on Orchids|journal=Philosophy of Science|volume=73|issue=5|pages=629–641|doi=10.1086/518332|s2cid=170396888|issn=0031-8248}}</ref> However, like Lamarck, he acknowledged that variability could also be introduced by patterns of use and disuse of organs.<ref name=":3">{{Cite journal|last=Deichmann|first=Ute|date=2010|title=Gemmules and Elements: On Darwin's and Mendel's Concepts and Methods in Heredity|jstor=20722529|journal=Journal for General Philosophy of Science|volume=41|issue=1|pages=85–112|doi=10.1007/s10838-010-9122-0|s2cid=42385140|issn=0925-4560}}</ref> Darwin was fascinated by variation in both natural and domesticated populations, and his realization that individuals in a population exhibited seemingly purposeless variation was largely driven by his experiences working with animal breeders.<ref>{{Cite journal|last=Bowler|first=Peter J.|date=2009-01-09|title=Darwin's Originality |journal=Science|volume=323|issue=5911|pages=223–226|doi=10.1126/science.1160332|pmid=19131623|s2cid=1170705|issn=0036-8075}}</ref> Darwin believed that species changed gradually, through the accumulation of small, continuous variations, a concept that would remain hotly contested into the 20th century.<ref name=":4">{{Cite book|last=Provine|first=William B. |title=The origins of theoretical population genetics|date=2001|publisher=University of Chicago Press|isbn=0-226-68463-6|edition=2nd |location=Chicago|oclc=46660910}}</ref>