Editing On the Origin of Species (section)

===Variation and heredity===
In Darwin's time there was no agreed-upon model of [[heredity]];<ref>{{harvnb|Larson|2004|p=85}}</ref> in Chapter I Darwin admitted, "The laws governing inheritance are quite unknown."<ref>{{harvnb|Darwin|1859|p=[http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=text&pageseq=28 13]}}</ref> He accepted a version of the inheritance of acquired characteristics (which after Darwin's death came to be called [[Lamarckism]]), and Chapter V discusses what he called the effects of use and disuse; he wrote that he thought "there can be little doubt that use in our domestic animals strengthens and enlarges certain parts, and disuse diminishes them; and that such modifications are inherited", and that this also applied in nature.<ref>{{harvnb|Darwin|1859|p=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F373&pageseq=152 134]}}</ref> Darwin stated that some changes that were commonly attributed to use and disuse, such as the loss of functional wings in some island-dwelling insects, might be produced by natural selection. In later editions of ''Origin'', Darwin expanded the role attributed to the inheritance of acquired characteristics. Darwin also admitted ignorance of the source of inheritable variations, but speculated they might be produced by environmental factors.<ref>{{harvnb|Larson|2004|pp=86–87}}</ref><ref>{{harvnb|Darwin|1859|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F373&pageseq=149 131–150]}}</ref> However, one thing was clear: whatever the exact nature and causes of new variations, Darwin knew from observation and experiment that breeders were able to select such variations and produce huge differences in many generations of selection.<ref name=rez /> The ''observation'' that selection works in domestic animals is not destroyed by lack of ''understanding'' of the underlying hereditary mechanism.

Breeding of animals and plants showed related varieties varying in similar ways, or tending to revert to an ancestral form, and similar patterns of variation in distinct species were explained by Darwin as demonstrating [[common descent]]. He recounted how [[Lord Morton's mare]] apparently demonstrated [[telegony (pregnancy)|telegony]], offspring inheriting characteristics of a previous mate of the female parent, and accepted this process as increasing the variation available for natural selection.<ref>{{Harvnb|Quammen|2006|pp=159–167}}</ref><ref>{{harvnb|Darwin|1859|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F373&pageseq=177 159–167]}}</ref>

More detail was given in Darwin's 1868 book on ''[[The Variation of Animals and Plants Under Domestication]]'', which tried to explain heredity through his hypothesis of [[pangenesis]]. Although Darwin had privately questioned [[blending inheritance]], he struggled with the theoretical difficulty that novel individual variations would tend to blend into a population. However, inherited variation could be seen,<ref name="flowering of genetics">{{cite web |url=https://www.theguardian.com/books/2003/feb/08/peopleinscience.evolution |title=An early flowering of genetics, Books |author=Richard Dawkins |author-link=Richard Dawkins |date=8 February 2003 |work=The Guardian |location=UK |access-date=24 October 2010}}</ref> and Darwin's concept of selection working on a population with a range of small variations was workable.<ref name="Bowler 200">{{Harvnb|Bowler|2003|pp=200–201}}</ref> It was not until the [[Extended evolutionary synthesis|modern evolutionary synthesis]] in the 1930s and 1940s that a model of heredity became completely integrated with a model of variation.<ref>{{Harvnb|Bowler|1989}}</ref> This modern evolutionary synthesis had been dubbed Neo Darwinian Evolution because it encompasses [[Charles Darwin]]'s theories of evolution with [[Gregor Mendel]]'s theories of genetic inheritance.<ref>McBride, P. D., Gillman, L. N., & Wright, S. D. (2009). Current debates on the origin of species. Journal of Biological Education, 43(3), 104–107.</ref>