Editing Genetic variation (section)

=== Pre-Darwinian concepts of heritable variation ===
In the mid-1700s, [[Pierre Louis Maupertuis]], a French scholar now known primarily for his work in mathematics and physics, posited that while species have a true, original form, accidents during the development of nascent offspring could introduce variations that could accumulate over time.<ref name=":0">{{Cite book|last=Bowler|first=Peter J. |title=Evolution: the history of an idea|date=1989|publisher=University of California Press|isbn=0-520-06385-6|edition=Rev. |location=Berkeley|oclc=17841313}}</ref> In his 1750 ''Essaie de Cosmologie'', he proposed that the species we see today are only a small fraction of the many variations produced by "a blind destiny", and that many of these variations did not "conform" to their needs, thus did not survive.<ref>{{Cite journal|last=Glass|first=Bentley|date=1947|title=Maupertuis and the Beginnings of Genetics |journal=The Quarterly Review of Biology|volume=22|issue=3|pages=196–210|doi=10.1086/395787|pmid=20264553|s2cid=28185536|issn=0033-5770}}</ref> In fact, some historians even suggest that his ideas anticipated the laws of inheritance further developed by [[Gregor Mendel]].<ref>{{Cite journal|last=Sandler|first=Iris|date=1983|title=Pierre Louis Moreau de Maupertuis: A precursor of Mendel? |journal=Journal of the History of Biology|volume=16|issue=1|pages=102|doi=10.1007/bf00186677|pmid=11611246|s2cid=26835071|issn=0022-5010}}</ref>

Simultaneously, French philosopher [[Denis diderot|Denis Diderot]] proposed a different framework for the generation of heritable variation. Diderot borrowed Maupertuis' idea that variation could be introduced during reproduction and the subsequent growth of offspring,<ref name=":1">{{Cite book|last=Gregory|first=Mary|doi=10.4324/9780203943823|title=Diderot and the Metamorphosis of Species|date=2006-10-23|publisher=Routledge|isbn=978-1-135-91583-4}}</ref> and thought that production of a "normal" organism was no more probable than production of a "monstrous" one.<ref>{{Cite journal|last=Hill|first=Emita|date=1968|title=Materialism and Monsters in "Le Rêve de d'Alembert"|jstor=40372379|journal=Diderot Studies|volume=10|pages=67–93|issn=0070-4806}}</ref> However, Diderot also believed that matter itself had lifelike properties and could self-assemble into structures with the potential for life.<ref name=":1" /> Diderot's ideas on biological transformation, introduced in his 1749 work [[Denis Diderot#Letter on the Blind|''Letter on the Blind'']], were thus focused on variability of spontaneously generated forms, not variability within existing species.<ref>{{Cite journal|last=Zirkle|first=Conway|date=1941|title=Natural Selection before the "Origin of Species"|jstor=984852|journal=Proceedings of the American Philosophical Society|volume=84|issue=1|pages=71–123|issn=0003-049X}}</ref>

Both Maupertuis and Diderot built on the ideas of  Roman poet and philosopher [[Lucretius]], who wrote in ''De rerum natura'' that all the universe was created by random chance, and only the beings that were not self-contradictory survived.<ref name=":2">{{Cite book|last=Gregory|first=Mary Efrosini |title=Evolutionism in eighteenth-century French thought|date=2008|publisher=Peter Lang|isbn=978-1-4331-0373-5|location=New York|oclc=235030545}}</ref> Maupertuis' work is distinguished from the work of both Lucretius and Diderot in his use of the concept of conformity in explaining differential survival of beings, a new idea among those who believed that life changed over time.<ref name=":2" />

Like Diderot, two other influential minds of the 18th century—[[Erasmus Darwin]] and [[Jean-Baptiste Lamarck]]—believed that only very simple organisms could be generated by spontaneous generation, so another mechanism was necessary to generate the great variability of complex life observed on earth.<ref name=":0" /> Erasmus Darwin proposed that changes acquired during an animal's life could be passed to its offspring, and that these changes seemed to be produced by the animal's endeavors to meet its basic needs.<ref>{{Cite journal|last=Zirkle|first=Conway|date=1946|title=The Early History of the Idea of the Inheritance of Acquired Characters and of Pangenesis|jstor=1005592|journal=Transactions of the American Philosophical Society|volume=35|issue=2|pages=91–151|doi=10.2307/1005592|issn=0065-9746}}</ref> Similarly, Lamarck's theory of the variability among living things was rooted in patterns of use and disuse, which he believed led to heritable physiological changes.<ref name=":0" /> Both Erasmus Darwin and Lamarck believed that variation, whether it arose during development or during the animal's life, was heritable, a key step in theories of change over time extending from individuals to populations.

In the subsequent century, [[William Herschel]]'s telescopic observations of diverse nebulae across the night sky suggested to him that different nebulae could each be in different stages in the process of condensation. This idea, which came to be known as the [[nebular hypothesis]], suggested that natural processes could both create order out of matter and introduce variation, and that these processes could be observed over time.<ref name=":0" />&nbsp;While it may seem to the modern reader that astronomical theories are irrelevant to theories of organic variation, these ideas became significantly conflated with ideas of biological transformation—what we now know as evolution—in the mid-19th century, laying important groundwork for the work of subsequent thinkers such as Charles Darwin.<ref>{{Cite journal|last=Schweber|first=S.S.|date=1989|title=John Herschel and Charles Darwin: A study in parallel lives |journal=Journal of the History of Biology|volume=22|issue=1|pages=1–71 |doi=10.1007/bf00209603|s2cid=122572397|issn=0022-5010}}</ref>