View source for Spontaneous generation

{{Short description|Theory of life arising from non-living matter}}
{{About|historical theories on the ongoing emergence of life|the origin of life|Abiogenesis}}
{{Good article}}

[[File:Spontaneous Generation of Seashells.svg|thumb|upright=1.35|Spontaneous generation of seashells, according to [[Aristotle]], varied with the nature of the seabed. Slime gave rise to [[oyster]]s; sand, to [[scallop]]s; and the hollows of rocks, to [[limpet]]s and [[barnacle]]s. People kept on wondering, though, whether the eggs of these animals might not be central to the generation process.<ref name="Bondeson 2018">{{cite book |last=Bondeson |first=Jan |title=The Feejee Mermaid and Other Essays in Natural and Unnatural History |chapter=Spontaneous Generation |publisher=[[Cornell University Press]] |publication-place=Ithaca, New York |date=31 December 2018 |doi=10.7591/9781501722271-009 |pages=193–249|isbn=9781501722271 }}</ref>]]

'''Spontaneous generation''' is a [[Superseded scientific theories|superseded scientific theory]] that held that living creatures could arise from [[abiotic component|non-living matter]] and that such processes were commonplace and regular. It was [[Hypothesis|hypothesized]] that certain forms, such as [[flea]]s, could arise from inanimate matter such as dust, or that [[maggot]]s could arise from dead flesh. The [[doctrine]] of spontaneous generation was coherently synthesized by the Greek philosopher and naturalist [[Aristotle]], who compiled and expanded the work of [[Pre-Socratic philosophy|earlier natural philosophers]] and the various ancient explanations for the appearance of [[organism]]s. Spontaneous generation was taken as scientific fact for two millennia. Though challenged in the 17th and 18th centuries by the experiments of the Italian biologists [[Francesco Redi]] and [[Lazzaro Spallanzani]], it was not discredited until the work of the French chemist [[Louis Pasteur]] and the Irish physicist [[John Tyndall]] in the mid-19th century.

Among biologists, rejecting spontaneous genesis is no longer controversial. Experiments conducted by Pasteur and others were thought to have refuted the conventional notion of spontaneous generation by the mid-1800s. Since all life appears to have [[Common descent|evolved from a single form]] approximately four billion years ago, attention has instead turned to the [[abiogenesis|origin of life]].

== Description ==
"Spontaneous generation" means both the supposed processes by which different types of life might repeatedly emerge from specific sources other than seeds, eggs, or parents, and the theoretical principles presented in support of any such phenomena. Crucial to this [[doctrine]] are the ideas that life comes from non-life and that no causal agent, such as a parent, is needed. Supposed examples included the seasonal generation of mice and other animals from the mud of the [[Nile]], the emergence of [[flea]]s from inanimate matter such as dust, or the appearance of [[maggot]]s in dead flesh.<ref name="Ball">{{cite journal |last=Ball |first=Philip |title=Man Made: A History of Synthetic Life |journal=Distillations |date=2016 |volume=2 |issue=1 |pages=15–23 |url=https://www.sciencehistory.org/distillations/magazine/man-made-a-history-of-synthetic-life |access-date=22 March 2018 |archive-date=26 December 2017 |archive-url=https://web.archive.org/web/20171226003739/https://www.chemheritage.org/distillations/magazine/man-made-a-history-of-synthetic-life |url-status=live }}</ref><ref>Stillingfleet, Edward. ''Origines Sacrae''. Cambridge University Press, 1697. [https://archive.org/details/originessacraeor00stil]</ref> Such ideas have something in common with the modern [[hypothesis]] of the [[abiogenesis|origin of life]], which asserts that life emerged some four billion years ago from non-living materials, over a time span of millions of years, and subsequently diversified into all the forms that now exist.<ref name="Bernal 1967">{{cite book |last=Bernal |first=J. D. |year=1967 |orig-year=Reprinted work by [[Alexander Oparin|A. I. Oparin]] originally published 1924; Moscow: [[Publishing houses in the Soviet Union|The Moscow Worker]] |title=The Origin of Life |url=https://archive.org/details/originoflife0000bern |url-access=registration |series=The Weidenfeld and Nicolson Natural History |others=Translation of Oparin by Ann Synge |location=London |publisher=[[Weidenfeld & Nicolson]] |lccn=67098482 }}</ref><ref name="Woese Fox 1977">{{cite journal |last1=Woese |first1=Carl R. |author1-link=Carl Woese |last2=Fox |first2=G. E. |year=1977 |title=Phylogenetic structure of the prokaryotic domain: the primary kingdoms. |journal=[[PNAS]] |volume=7 |issue=11 |pages=5088–5090 |bibcode=1977PNAS...74.5088W |doi=10.1073/pnas.74.11.5088 |pmc=432104 |pmid=270744 |doi-access=free}}</ref>

The term ''equivocal generation'', sometimes known as ''heterogenesis'' or ''xenogenesis'', describes the supposed process by which one form of life arises from a different, unrelated form, such as [[Eucestoda|tapeworm]]s from the bodies of their hosts.<ref>{{cite book |editor-last=Wiener |editor-first=Philip P. |title=Dictionary of the History of Ideas |year=1973 |publisher=Charles Scribner's Sons |location=New York |chapter=Spontaneous Generation |chapter-url=http://ftp.mpdl.mpg.de/mpiwg-berlin/data/datastreams-single/escidoc_643819+content+content.0 |volume=4 |pages=307–311 |archive-url=https://web.archive.org/web/20210706192951/http://ftp.mpdl.mpg.de/mpiwg-berlin/data/datastreams-single/escidoc_643819+content+content.0 |archive-date=6 July 2021 }}</ref><ref>{{cite journal |last=McLaughlin |first=Peter |title=Spontaneous versus equivocal generation in early modern science |journal=Annals of the History and Philosophy of Biology |date=2006 |volume=10 |pages=79–88 |url=http://ftp.mpdl.mpg.de/mpiwg-berlin/data/datastreams-single/escidoc_643819+content+content.0 |access-date=6 February 2021 |archive-date=20 November 2021 |archive-url=https://web.archive.org/web/20211120094628/http://ftp.mpdl.mpg.de/mpiwg-berlin/data/datastreams-single/escidoc_643819+content+content.0 |url-status=dead }}</ref>

== Antiquity ==

=== Pre-Socratic philosophers ===

Active in the 6th and 5th centuries BCE, early Greek philosophers, called ''physiologoi'' in antiquity (Greek: φυσιολόγοι; in English, physical or [[Natural philosophy|natural philosophers]]), attempted to give natural explanations of [[phenomena]] that had previously been ascribed to the agency of the gods.<ref>{{cite book | last=Guthrie |first=William Keith Chambers |author-link=W. K. C. Guthrie |title=The Presocratic Tradition from Parmenides to Democritus |date=June 1965 |page=13 |publisher=Cambridge University Press |isbn=0-317-66577-4 |url=https://archive.org/details/historyofgreekph0002unse}}</ref> The ''physiologoi'' sought the material principle or ''[[arche]]'' (Greek: ἀρχή) of things, emphasizing the rational unity of the external world and rejecting theological or mythological explanations.<ref name="seyffert480">{{cite book |last=Seyffert |first=Oskar |year=2017 |orig-date=1894 |title=Dictionary of Classical Antiquities |publisher=Norderstedt Hansebooks |page=480 |isbn=978-3337196868 |url=https://archive.org/details/dictionaryofclas00seyfrich/page/n3/mode/2up }}</ref>

[[Anaximander]], who believed that all things arose from the elemental nature of the universe, the ''[[Apeiron (cosmology)|apeiron]]'' (ἄπειρον) or the "unbounded" or "infinite", was likely the first western thinker to propose that life developed spontaneously from nonliving matter. The [[substance theory|primal chaos]] of the ''apeiron,'' eternally in motion, served as a platform on which elemental opposites (e.g., ''wet and dry'', ''hot and cold'') generated and shaped the many and varied things in the world.<ref>{{cite book |title=The Legacy of Parmenides: Eleatic Monism and Later Presocratic Thought |author=Curd, Patricia |year=1998 |publisher=[[Princeton University Press]] |page=77 |isbn=0-691-01182-6 |url=https://books.google.com/books?id=x2JX1ulXzogC&pg=PA77}}</ref> According to [[Hippolytus of Rome]] in the third century CE, Anaximander claimed that fish or fish-like creatures were first formed in the "wet" when acted on by the heat of the sun and that these aquatic creatures gave rise to human beings.<ref>{{cite book |last1=Kahn |first1=Charles H. |author-link = Charles H. Kahn |title=Anaximander and the Origins of Greek Cosmology |date=1994 |publisher=Hackett Publishing |isbn=0872202550 |pages=247 |url=https://archive.org/details/anaximanderorigi00kahn/page/n9/mode/2up}}</ref> The Roman author [[Censorinus]], writing in the 3rd century, reported:

{{quote|text=Anaximander of Miletus considered that from warmed up water and earth emerged either fish or entirely fishlike animals. Inside these animals, men took form and embryos were held prisoners until puberty; only then, after these animals burst open, could men and women come out, now able to feed themselves.<ref>[[Censorinus]], ''[https://archive.org/details/b30335978/page/n11/mode/2up?view=theater De Die Natali]'', IV, 7</ref>}}

The Greek philosopher [[Anaximenes of Miletus|Anaximenes]], a pupil of Anaximander, thought that air was the element that imparted life and endowed creatures with motion and thought. He proposed that plants and animals, including human beings, arose from a primordial terrestrial slime, a mixture of earth and water, combined with the sun's heat. The philosopher [[Anaxagoras]], too, believed that life emerged from a terrestrial slime. However, Anaximenes held that the seeds of plants existed in the air from the beginning, and those of animals in the [[Aether (classical element)|aether]]. Another philosopher, [[Xenophanes]], traced the origin of man back to the transitional period between the fluid stage of the Earth and the formation of land, under the influence of the Sun.<ref>{{cite book |last=Osborn |first=Henry Fairfield |author-link=Henry Fairfield Osborn |title=From the Greeks to Darwin: An outline of the development of the evolution idea|url=https://archive.org/details/fromgreekstodar01osbogoog |date=1894 |publisher=Macmillan |location=New York}}</ref>

In what has occasionally been seen as a prefiguration of a concept of [[natural selection]], [[Empedocles]] accepted the spontaneous generation of life, but held that different forms, made up of differing combinations of parts, spontaneously arose as though by trial and error: successful combinations formed the individuals present in the observer's lifetime, whereas unsuccessful forms failed to reproduce.<ref>{{cite journal |last=Zirkle |first=Conway |author-link=Conway Zirkle |title=Natural Selection before the "Origin of Species" |journal=Proceedings of the American Philosophical Society |date=1941 |volume=84 |issue=1 |pages=71–123 |jstor=984852 |url=https://www.jstor.org/stable/984852 |access-date=4 January 2023 |archive-date=31 March 2023 |archive-url=https://web.archive.org/web/20230331015709/https://www.jstor.org/stable/984852 |url-status=live }}</ref>

=== Aristotle ===
{{further|Aristotle's biology}}

In [[Aristotle's biology|his biological works]], the natural philosopher [[Aristotle]] theorized extensively the reproduction of various animals, whether by [[sexual reproduction|sexual]], [[parthenogenesis|parthenogenetic]], or spontaneous generation. In accordance with his fundamental theory of [[hylomorphism]], which held that every physical entity was a compound of matter and form, Aristotle's basic theory of sexual reproduction contended that the [[semen|male's seed]] imposed form, the set of characteristics passed down to offspring on the "matter" ([[menstrual blood]]) supplied by the female. Thus female matter is the ''[[Four causes#Matter|material cause]]'' of generation—it supplies the matter that will constitute the offspring—while the male semen is the ''[[Four causes#Agent|efficient cause]]'', the factor that instigates and delineates the thing's existence.<ref name=Leroi2014>{{cite book |last=Leroi |first=Armand Marie |author-link=Armand Marie Leroi |title=The Lagoon: How Aristotle Invented Science |title-link=Aristotle's Lagoon |publisher=Bloomsbury |date=2014 |isbn=978-1-4088-3622-4 |pages=215–221}}</ref><ref>{{cite book |editor-last=Brack |editor-first=André |title=The Molecular Origins of Life |year=1998 |publisher=Cambridge University Press |isbn=978-0-521-56475-5 |page=[https://archive.org/details/molecularorigins0000brac/page/1 1] |chapter=Introduction |chapter-url=http://assets.cambridge.org/97805215/64755/excerpt/9780521564755_excerpt.pdf |url=https://archive.org/details/molecularorigins0000brac/page/1 }}</ref> Yet, Aristotle proposed in the ''[[History of Animals]]'', many creatures form not through sexual processes but by spontaneous generation:

{{quote|Now there is one property that animals are found to have in common with plants. For some plants are generated from the seed of plants, whilst other plants are self-generated through the formation of some elemental principle similar to a seed; and of these latter plants some derive their nutriment from the ground, whilst others grow inside other plants ... So with animals, some spring from parent animals according to their kind, whilst others grow spontaneously and not from kindred stock; and of these instances of spontaneous generation some come from putrefying earth or vegetable matter, as is the case with a number of insects, while others are spontaneously generated in the inside of animals out of the secretions of their several organs.<ref name="HistAnimV">{{cite book |author=Aristotle |author-link=Aristotle |others=translated by D'Arcy Wentworth Thompson |title=History of Animals |url=https://ebooks.adelaide.edu.au/a/aristotle/history/complete.html |orig-year=c. 343 BCE |year=1910 |publisher=Clarendon Press |location=Oxford |chapter=Book V |chapter-url=http://ebooks.adelaide.edu.au/a/aristotle/history/book5.html |isbn=978-90-6186-973-3 |access-date=7 January 2009 |archive-date=8 May 2018 |archive-url=https://web.archive.org/web/20180508025913/https://ebooks.adelaide.edu.au/a/aristotle/history/ |url-status=dead }}</ref>|Aristotle|''[[History of Animals]]'', Book V, Part 1}}

According to this theory, living things may come forth from nonliving things in a manner roughly analogous to the "enformation of the female matter by the agency of the male seed" seen in sexual reproduction.<ref name=Lehoux2017p22>{{cite book |last1=Lehoux |first1=Daryn |title=Creatures Born of Mud and Slime: The Wonder and Complexity of Spontaneous Generation |date=2017 |publisher=Johns Hopkins University Press |location=Baltimore |page=22 |isbn=9781421423814 |url=https://books.google.com/books?id=E749DwAAQBAJ}}</ref> Nonliving materials, like the seminal fluid present in sexual generation, contain ''[[pneuma]]'' (πνεῦμα, "breath"), or "[[vital heat]]". According to Aristotle, ''pneuma'' had more "heat" than regular air did, and this heat endowed the substance with certain vital properties:

{{quote|The power of every soul seems to have shared in a different and more divine body than the so called [four] elements ... For every [animal], what makes the seed generative inheres in the seed and is called its "heat". But this is not fire or some such power, but instead the ''pneuma'' that is enclosed in the seed and in foamy matter, this being analogous to the element of the stars. This is why fire does not generate any animal{{nbsp}}... but the heat of the sun and the heat of animals does, not only the heat that fills the seed, but also any other residue of [the animal's] nature that may exist similarly possesses this vital principle.|Aristotle|''[[Generation of Animals]]'', 736b29ff.<ref>{{cite book |last1=Lehoux |first1=Daryn |title=Creatures Born of Mud and Slime: The Wonder and Complexity of Spontaneous Generation |date=2017 |publisher=Johns Hopkins University Press |location=Baltimore |page=23}}</ref>}}

Aristotle drew an analogy between the "foamy matter" (τὸ ἀφρῶδες, ''to aphrodes'') found in nature and the "seed" of an animal, which he viewed as being a kind of foam itself (composed, as it was, from a mixture of water and ''pneuma''). For Aristotle, the generative materials of male and female animals (semen and menstrual fluid) were essentially refinements, made by male and female bodies according to their respective proportions of heat, of ingested food, which was, in turn, a byproduct of the elements earth and water. Thus any creature, whether generated sexually from parents or spontaneously through the interaction of vital heat and elemental matter, was dependent on the proportions of ''pneuma'' and the various elements which Aristotle believed comprised all things.<ref>{{cite book |last1=Lehoux |first1=Daryn |title=Creatures Born of Mud and Slime |date=2017 |publisher=Johns Hopkins University Press |pages=26–28}}</ref> While Aristotle recognized that many living things emerged from [[Putrefaction|putrefying]] matter, he pointed out that the putrefaction was not the source of life, but the byproduct of the action of the "sweet" element of water.<ref>{{cite book |author=Aristotle |author-link=Aristotle |others=translated by Arthur Platt |title=On the Generation of Animals |url=https://ebooks.adelaide.edu.au/a/aristotle/generation/complete.html |access-date=2009-01-09 |orig-year=c. 350 BCE |year=1912 |publisher=Clarendon Press |location=Oxford |chapter=Book III |chapter-url=http://ebooks.adelaide.edu.au/a/aristotle/generation/book3.html |isbn=90-04-09603-5 |archive-date=2015-09-10 |archive-url=https://web.archive.org/web/20150910034528/https://ebooks.adelaide.edu.au/a/aristotle/generation/complete.html |url-status=dead }}</ref>

{{quote|Animals and plants come into being in earth and in liquid because there is water in earth, and air in water, and in all air is vital heat so that in a sense all things are full of soul. Therefore living things form quickly whenever this air and vital heat are enclosed in anything. When they are so enclosed, the corporeal liquids being heated, there arises as it were a frothy bubble.|Aristotle|''[[Generation of Animals]]'', Book III, Part 11}}

With varying degrees of observational confidence, Aristotle theorized the spontaneous generation of a range of creatures from different sorts of inanimate matter. The [[testacea]]ns (a genus which for Aristotle included [[bivalvia|bivalves]] and snails), for instance, were characterized by spontaneous generation from mud, but differed based upon the precise material they grew in—for example, [[clam]]s and [[scallop]]s in sand, [[oyster]]s in slime, and the [[barnacle]] and the [[limpet]] in the hollows of rocks.<ref name=HistAnimV/>

=== Latin and early Christian sources ===

Athenaeus dissented towards spontaneous generation, claiming that a variety of [[anchovy]] did not generate from [[roe]], as Aristotle stated, but rather, from [[sea foam]].<ref>{{cite book |author=Athenaeus of Naucratis |author-link=Athenaeus |editor-last=Yonge |editor-first=C. D. |title=The deipnosophists, or, Banquet of the learned of Athenæus |url=http://digicoll.library.wisc.edu/cgi-bin/Literature/Literature-idx?type=article&did=Literature.AthV1.i0010&id=Literature.AthV1&isize=M&pview=hide |series=University of Wisconsin Digital Collection |volume= I |publisher=Henry G. Bohn |location=London |pages=433–521 |chapter=Book VII |archive-url=https://web.archive.org/web/20121021022851/http://digicoll.library.wisc.edu/cgi-bin/Literature/Literature-idx?type=article&did=Literature.AthV1.i0010&id=Literature.AthV1&isize=M&pview=hide |archive-date=21 October 2012 |chapter-url=http://digicoll.library.wisc.edu/cgi-bin/Literature/Literature-idx?type=article&did=LITERATURE.ATHV1.I0010&isize=M&pview=hide }}</ref>

As the dominant view of philosophers and thinkers continued to be in favour of spontaneous generation, some Christian [[Theology|theologians]] accepted the view. The Berber theologian and philosopher [[Augustine of Hippo]] discussed spontaneous generation in ''[[City of God (book)|The City of God]]'' and ''The Literal Meaning of Genesis'', citing Biblical passages such as "Let the waters bring forth abundantly the moving creature that hath life" ({{bibleverse||Genesis|1:20|KJV|}}) as decrees that would enable ongoing creation.<ref name="irisfry">{{cite book |last=Fry |first=Iris |title=The Emergence of Life on Earth |url=https://books.google.com/books?id=6KoRvUeUUuEC |chapter=Chapter 2: Spontaneous Generation – Ups and Downs |access-date=2009-01-21 |year=2000 |publisher=[[Rutgers University Press]] |isbn=978-0-8135-2740-6}}</ref>

== Middle Ages ==

{{multiple image
|total_width=400
|footer=In the [[Middle Ages]], it was thought that the goose barnacle gave birth to the barnacle goose, supporting the [[virgin birth of Jesus]].<ref name="Gerald of Wales"/>
|image1=Barnacle Geese Fac simile of an Engraving on Wood from the Cosmographie Universelle of Munster folio Basle 1552.png
|caption1=Barnacles turning into geese, in the 1552 ''[[Cosmographia (Sebastian Münster)|Cosmographia]]''
|image2=Pollicipes cornucopia.jpg
|caption2=The [[Pollicipes cornucopia|goose barnacle]]
|image3=Branta leucopsis.jpg
|caption3=The [[Branta leucopsis|barnacle goose]]
}}

From the [[decline of the Roman Empire|fall of the Roman Empire]] in 5th century to the [[East–West Schism]] in 1054, the influence of [[Greek science]] declined, although spontaneous generation generally went unchallenged. New descriptions were made. Of the beliefs, some had doctrinal implications. In 1188, [[Gerald of Wales]], after having traveled in Ireland, argued that the [[barnacle goose myth]] was evidence for the [[virgin birth of Jesus]].<ref name="Gerald of Wales">{{cite book |author=Giraldus Cambrensis |author-link=Gerald of Wales |title=Topographia Hiberniae |url=http://www.fordham.edu/halsall/source/1188geraldwales-barnacle.html |year=1188 |publisher=Humanities Press |isbn=0-85105-386-6 |archive-url=https://web.archive.org/web/20220509162745/https://sourcebooks.fordham.edu/source/1188geraldwales-barnacle.asp |archive-date=9 May 2022 |url-status=live}}</ref> Where the practice of fasting during [[Lent]] allowed fish, but prohibited fowl, the idea that the goose was in fact a fish suggested that its consumption be permitted during Lent. The practice was eventually prohibited by decree of [[Pope Innocent III]] in 1215.<ref>{{cite book |last=Lankester |first=Edwin Ray |author-link=Edwin Lankester |title=Diversions of a Naturalist |edition=illustrated |orig-year=1915 |year=1970 |publisher=Ayer Publishing |isbn=978-0-8369-1471-9 |pages=117–128 |chapter=XIV. The History of the Barnacle and the Goose |chapter-url=https://archive.org/details/diversionsofnatu0000lank_e1a6/page/n7/mode/2up }}</ref>

After Aristotle’s works were reintroduced to Western Europe, they were translated into Latin from the original Greek or Arabic. They reached their greatest level of acceptance during the 13th century. With the availability of Latin translations, the German philosopher [[Albertus Magnus]] and his student [[Thomas Aquinas]] raised Aristotelianism to its greatest prominence. Albert wrote a paraphrase of Aristotle, ''De causis et processu universitatis'', in which he removed some commentaries by Arabic scholars and incorporated others.<ref>{{Cite book |date=March 20, 2006 |contribution=Albert the Great |contribution-url=http://plato.stanford.edu/entries/albert-great/ |editor-last=Zalta |editor-first=Edward N. |editor-link=Edward N. Zalta |title=Stanford Encyclopedia of Philosophy |edition=Winter 2009 |location=Stanford, California |publisher=The Metaphysics Research Lab |oclc=179833493 |url=http://plato.stanford.edu/ |access-date=2009-01-23 |isbn=1-158-37777-0 |archive-date=27 December 1996 |archive-url=https://web.archive.org/web/19961227155812/http://plato.stanford.edu/ |url-status=live }}</ref> The influential writings of Aquinas, on both the physical and metaphysical, are predominantly Aristotelian, but show numerous other influences.<ref>{{Cite book |date=July 12, 1999 |publication-date=January 9, 2005 |contribution=Saint Thomas Aquinas |contribution-url=http://plato.stanford.edu/entries/aquinas/ |editor-last=Zalta |editor-first=Edward N. |editor-link=Edward N. Zalta |title=Stanford Encyclopedia of Philosophy |edition=Winter 2009 |location=Stanford, CA |publisher=The Metaphysics Research Lab |oclc=179833493 |url=http://plato.stanford.edu/ |access-date=2009-01-23 |isbn=1-158-37777-0 |archive-date=27 December 1996 |archive-url=https://web.archive.org/web/19961227155812/http://plato.stanford.edu/ |url-status=live }}</ref>

[[File:Trees that generate both fishes and birds. Wellcome M0005642.jpg|thumb|upright|[[Claude Duret]]'s 1605 ''Histoire admirable des plantes et herbes esmerueillables et miraculeuses en nature...'' illustrated numerous supposed examples of spontaneous generation,<ref name="Bondeson 2018"/> such as this tree generating both fishes and birds]]
Spontaneous generation is described in literature as if it were a fact well into the [[Renaissance]]. [[William Shakespeare|Shakespeare]] wrote of snakes and crocodiles forming from the mud of the [[Nile]]:<ref>{{Folger inline|Ant|2|7|24–28|bare=true}}</ref> 

{{quote|<poem>[[Marcus Aemilius Lepidus (triumvir)|Lepidus]]: You’ve strange serpents there?
[[Mark Antony|Antony]]: Ay, Lepidus.
Lepidus: Your serpent of Egypt is bred now of your mud by the operation of your sun; so is your crocodile.
Antony: They are so.
</poem> Shakespeare: ''[[Antony and Cleopatra]]'': Act 2, scene 7}}

The author of ''[[The Compleat Angler]]'', [[Izaak Walton]] repeats the question of the origin of eels "as rats and mice, and many other living creatures, are bred in Egypt, by the sun's heat when it shines upon the overflowing of the river...". While the ancient question of the origin of eels remained unanswered and the additional idea that eels reproduced from corruption of age was mentioned, the spontaneous generation of rats and mice stirred up no debate.<ref>{{cite book |last=Walton |first=Izaak |author-link=Izaak Walton |title=The Compleat Angler or the Contemplative Man's Recreation |url=https://commons.wikimedia.org/wiki/File:The_complete_angler,_or,_The_contemplative_man%27s_recreation_(IA_anglerorcomplete00waltrich).pdf |orig-year=1653 |year=1903 |publisher=George Bell & Sons |chapter=XIII. Observations of the eel, and other fish that want for scales, and how to fish for them |isbn=0-929309-00-6 |access-date=4 January 2023 |archive-date=14 March 2023 |archive-url=https://web.archive.org/web/20230314014948/https://commons.wikimedia.org/wiki/File%3AThe_complete_angler%2C_or%2C_The_contemplative_man%27s_recreation_%28IA_anglerorcomplete00waltrich%29.pdf |url-status=live }}</ref>

The Dutch biologist and microscopist [[Jan Swammerdam]] rejected the concept that one animal could arise from another or from putrification by chance because it was [[Impiety|impious]]; he found the concept of spontaneous generation irreligious, and he associated it with [[atheism]].<ref name="OslerFarber2002">{{cite book |last1=Osler |first1=Margaret J. |last2=Farber |first2=Paul Lawrence |title=Religion, Science, and Worldview: Essays in Honor of Richard S. Westfall|url=https://books.google.com/books?id=jbLWJPca_zoC&pg=PA236 |date=22 August 2002 |publisher=Cambridge University Press |isbn=978-0-521-52493-3 |pages=230–}}</ref>

== Previous beliefs ==

* [[Frog|Frogs]] were believed to have spontaneously generated from mud.<ref name=":0">{{Cite web |title=Spontaneous Generation in Antiquity –TAPA 51:101‑115 (1920) |url=http://penelope.uchicago.edu/Thayer/E/Journals/TAPA/51/Spontaneous_Generation*.html#:~:text=There%20was%20a%20well-established%20notion%20in%20antiquity%20that%20frogs%20were%20generated%20from%20mud,%E2%80%8B65%20an%20idea%20that%20persisted%20beyond%20the%20Middle%20Ages. |access-date=2023-05-22 |website=penelope.uchicago.edu}}</ref>
* [[Mouse|Mice]] were believed to become pregnant though the act of licking salt, or grew from the moisture of the earth.<ref name=":0" />
* [[Barnacle goose|Barnacle geese]] were thought to have emerged from a [[crustacean]], the [[goose barnacle]] (see the [[barnacle goose myth]]).
* [[Snake|Snakes]] could generate from the marrow of the human [[Vertebral column|spine]],<ref name=":0" /> and had previously generated from the blood of [[Medusa]].
* [[Eel|Eels]] had multiple stories. Aristotle claimed that [[eel]]s emerged from [[earthworm]]s, and were lacking in [[sex]] and [[milt]], [[spawn (biology)|spawn]] and passages for these.<ref>{{cite book |author=Aristotle |url=https://ebooks.adelaide.edu.au/a/aristotle/history/complete.html |title=The History of Animals |publisher=Clarendon Press |year=1910 |isbn=90-6186-973-0 |location=Oxford |translator=D'Arcy Wentworth Thompson |chapter=Book IV |author-link=Aristotle |access-date=2009-01-06 |chapter-url=http://ebooks.adelaide.edu.au/a/aristotle/history/book4.html |archive-url=https://web.archive.org/web/20171118011659/https://ebooks.adelaide.edu.au/a/aristotle/history/complete.html |archive-date=2017-11-18 |url-status=dead |orig-year=c. 343 BCE}}</ref><ref>{{cite book |author=Aristotle |url=https://ebooks.adelaide.edu.au/a/aristotle/history/complete.html |title=History of Animals |publisher=Clarendon Press |year=1910 |isbn=90-6186-973-0 |location=Oxford |translator=D'Arcy Wentworth Thompson |chapter=Book VI |author-link=Aristotle |access-date=2009-01-06 |chapter-url=http://ebooks.adelaide.edu.au/a/aristotle/history/book6.html |archive-url=https://web.archive.org/web/20171118011659/https://ebooks.adelaide.edu.au/a/aristotle/history/complete.html |archive-date=2017-11-18 |url-status=dead |orig-year=c. 343 BCE}}</ref> Later authors dissented. The Roman author and natural historian [[Pliny the Elder]] did not argue against the anatomic limits of eels, but stated that eels reproduce by budding, scraping themselves against rocks, liberating particles that become eels.<ref>{{cite book |author=Gaius Plinius Secundus |url=https://www.perseus.tufts.edu/cgi-bin/ptext?lookup=Plin.+Nat.+toc |title=Natural History |year=1855 |editor1-last=Bostock |editor1-first=John |editor1-link=John Bostock (physician) |volume=Book IX. The natural history of fishes |chapter=74. (50.) – The generation of fishes |author-link=Pliny the Elder |access-date=21 February 2021 |editor2-last=Riley |editor2-first=Henry Thomas |editor2-link=Henry Thomas Riley |chapter-url=https://www.perseus.tufts.edu/cgi-bin/ptext?doc=Perseus%3Atext%3A1999.02.0137&query=head%3D%23492 |archive-url=https://web.archive.org/web/20080915064348/http://www.perseus.tufts.edu/cgi-bin/ptext?lookup=Plin.+Nat.+toc |archive-date=15 September 2008 |url-status=live |orig-year=c. 77}}</ref> The Greek author [[Athenaeus]] described eels as entwining and discharging a fluid which would settle on mud and generate life. 
* [[Bookworm (insect)|Bookworms]] could generate from excessive wind. [[Vitruvius]], a [[Ancient Rome|Roman]] [[architect]] and writer of the 1st century BCE, advised that to stop their generation, [[libraries]] be placed facing eastwards to benefit from morning light, but not towards the south or the west as those winds were particularly offensive.<ref>{{cite book |author=Marcus Vitruvius Pollio |url=https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Vitruvius/home.html |title=On Architecture (de Architectura) |publisher=Priestley and Weale |others=electronic format by Bill Thayer |year=1826 |volume=Book VI |location=London |translator=Joseph Gwilt |chapter=Part 4 |author-link=Vitruvius |access-date=2009-02-03 |chapter-url=https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Vitruvius/6*.html#4.1 |orig-year=c. 25 BCE}}</ref>
* [[Bee|Bees]] were generated in decomposing cows, through a process known as [[bugonia]]. [[Samson's riddle]] led some to believe they could also generate through the body of a [[lion]]. 
* [[Wasp|Wasps]] could be generated from decomposing horses.
* [[Cicada]] were generated from the spittle of the [[cuckoo]].<ref name=":0" />

== Experimental approach==

=== Early tests ===

The Brussels physician [[Jan Baptist van Helmont]] described a recipe for mice (a piece of dirty cloth plus wheat for 21 days) and scorpions ([[basil]], placed between two bricks and left in sunlight). His notes suggest he may have attempted to do these things.<ref>{{Cite web |last=Pasteur |first=Louis |author-link=Louis Pasteur |date=7 April 1864 |title=On Spontaneous Generation |type=Address delivered by Louis Pasteur at the "Sorbonne Scientific Soirée" |url=http://shell.cas.usf.edu/~alevine/pasteur.pdf |access-date=1 July 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090326183109/http://shell.cas.usf.edu/~alevine/pasteur.pdf |archive-date=26 March 2009 }}</ref>

Where Aristotle held that the [[embryo]] was formed by a [[coagulation]] in the [[uterus]], the English physician [[William Harvey]] showed by way of [[dissection]] of [[deer]] that there was no visible embryo during the first month.<!--Bayon 1947 esp pp 73–75--> Although his work predated the [[microscope]], this led him to suggest that life came from invisible eggs. In the [[Book frontispiece|frontispiece]] of his 1651 book ''Exercitationes de Generatione Animalium'' (''Essays on the Generation of Animals''), he denied spontaneous generation with the motto ''omnia ex ovo'' ("everything from eggs").<ref name="irisfry"/><ref name="Bayon 1947">{{cite journal |last=Bayon |first=H. P. |title=William Harvey (1578–1657): His Application of Biological Experiment, Clinical Observation, and Comparative Anatomy to the Problems of Generation |journal=Journal of the History of Medicine and Allied Sciences |date=1947 |volume=2 |issue=1 |pages=51–96 |doi=10.1093/jhmas/II.1.51 |jstor=24619518 |pmid=20242557 |url=https://www.jstor.org/stable/24619518 |access-date=4 January 2023 |archive-date=25 January 2023 |archive-url=https://web.archive.org/web/20230125230800/https://www.jstor.org/stable/24619518 |url-status=live |url-access=subscription }}</ref>

[[File:Illustration of Redi's 1668 experiment to refute spontaneous generation.svg|thumb|upright=1.5|Illustration of Redi's 1668 experiment to refute spontaneous generation]]

The ancient beliefs were subjected to testing. In 1668, the Italian physician and parasitologist [[Francesco Redi]] challenged the idea that maggots arose spontaneously from rotting meat. In the first major [[experiment]] to challenge spontaneous generation, he placed meat in a variety of sealed, open, and partially covered containers.<ref name="slowdeath">{{Cite web |last1=Levine |first1=Russell |last2=Evers |first2=Chris |url=http://webprojects.oit.ncsu.edu/project/bio183de/Black/cellintro/cellintro_reading/Spontaneous_Generation.html |title=The Slow Death of Spontaneous Generation (1668–1859) |access-date=December 19, 2008 |year=1999 |publisher=National Health Museum |location=Washington, D.C.|archive-url=https://web.archive.org/web/20160124023828/http://webprojects.oit.ncsu.edu/project/bio183de/Black/cellintro/cellintro_reading/Spontaneous_Generation.html |archive-date=24 January 2016 }}</ref> Realizing that the sealed containers were deprived of air, he used "fine Naples veil", and observed no worms on the meat, but they appeared on the cloth.<ref name="fredi">{{cite book |last=Redi |first=Francesco |author-link=Francesco Redi |translator=Mab Bigelow |title=Experiments on the Generation of Insects |url=https://archive.org/details/experimentsonge00bigegoog |orig-year=1669 |year=1909 |publisher=Open Court |location=Chicago }}</ref> Redi used his experiments to support the preexistence theory put forth by the Catholic Church at that time, which maintained that living things originated from parents.<ref name="Fry2000">{{cite book |last=Fry |first=Iris |title=Emergence of Life on Earth: A Historical and Scientific Overview |url=https://books.google.com/books?id=6KoRvUeUUuEC |date= 2000 |publisher=Rutgers University Press |isbn=978-0-8135-2740-6 |pages=27–}}</ref> In scientific circles Redi's work very soon had great influence, as evidenced in a letter from the English [[Natural theology|natural theologian]] [[John Ray]] in 1671 to members of the [[Royal Society]] of London, in which he calls the spontaneous generation of insects "unlikely".<ref>{{cite journal |title=Hutton, Charles, 1737–1823; Shaw, George, 1751–1813; Pearson, Richard, 1765–1836. The Extract of a Letter written by Mr. JOHN RAY, to the Editor, from Middleton, July 3, 1671, concerning Spontaneous Generation;... Number 73, p. 2219. |journal=The Philosophical Transactions of the Royal Society of London, from Their Commencement in 1665 |year=1800 |pages=617–618 |url=https://archive.org/details/philosophicaltra01royarich}}</ref>

[[Pier Antonio Micheli]], {{circa|1729}}, observed that when fungal [[spore]]s were placed on slices of melon, the same type of fungi were produced that the spores came from, and from this observation he noted that fungi did not arise from spontaneous generation.<ref name="Agrios2005">{{cite book |last=Agrios |first=George N. |title=Plant Pathology |url=https://books.google.com/books?id=CnzbgZgby60C&pg=PA17 |access-date=14 August 2012 |year=2005 |publisher=Academic Press |isbn=978-0-12-044565-3 |pages=17–}}</ref>

In 1745, [[John Needham]] performed a series of experiments on boiled [[broth]]s. Believing that boiling would kill all living things, he showed that when sealed right after boiling, the broths would cloud, allowing the belief in spontaneous generation to persist. His studies were rigorously scrutinized by his peers, and many of them agreed.<ref name="slowdeath"/>

[[Lazzaro Spallanzani]] did an extensive variety of observations and experiments that modified the experiments of Needham in 1768, where he attempted to exclude the possibility of introducing a contaminating factor between boiling and sealing. His technique involved boiling the broth in a sealed container with the air partially [[Vacuum|evacuated]] to prevent explosions. Although he did not see growth, the exclusion of air left the question of whether air was an essential factor in spontaneous generation.<ref name="slowdeath"/> But attitudes were changing; by the start of the 19th century, a scientist such as [[Joseph Priestley]] could write that "There is nothing in modern philosophy that appears to me so extraordinary, as the revival of what has long been considered as the exploded doctrine of equivocal, or, as Dr. [Erasmus] Darwin calls it, spontaneous generation."<ref>{{cite journal |last=Priestley |first=Joseph |author-link=Joseph Priestley |title=Observations and Experiments relating to equivocal, or spontaneous, Generation |journal=[[Transactions of the American Philosophical Society]] |year=1809 |volume=VI |pages=119–129 |url=https://archive.org/details/transactionsofam61809amer }}</ref>

In 1837, [[Charles Cagniard de la Tour]], a physicist, and [[Theodor Schwann]], one of the founders of cell theory, published their independent discovery of [[yeast]] in [[alcoholic fermentation]]. They used the microscope to examine foam left over from the process of [[brewing]] beer. Where the Dutch microscopist [[Antonie van Leeuwenhoek]] described "small spheroid globules", they observed yeast cells undergo [[cell division]]. Fermentation would not occur when sterile air or pure oxygen was introduced if yeast were not present. This suggested that airborne [[microorganism]]s, not spontaneous generation, was responsible.<ref>{{cite journal |last=Springer |first=Alfred |date=October 13, 1892 |title=The Micro-organisms of the Soil |journal=Nature |volume=46 |issue=1198 |pages=576–579 |url=https://books.google.com/books?id=LHkCAAAAIAAJ&pg=PT138 |doi=10.1038/046576b0 |bibcode=1892Natur..46R.576. |s2cid=4037475 |url-access=subscription }}</ref>

However, although the idea of spontaneous generation had been in decline for nearly a century, its supporters did not abandon it all at once. As [[James Rennie (naturalist)|James Rennie]] wrote in 1838, despite Redi's experiments, "distinguished naturalists, such as [[Johann Friedrich Blumenbach|Blumenbach]], [[Georges Cuvier|Cuvier]], [[Jean Baptiste Bory de Saint-Vincent|Bory de St. Vincent]], [[Robert Brown (botanist, born 1773)|R. Brown]], &c." continued to support the theory.<ref name=JRIT>{{cite book | url=https://archive.org/details/insecttransforma00renn |last=Rennie |first=James |title=Insect Transformations |publisher=Charles Knight |year=1838 |page=10}}</ref>

===Pasteur and Tyndall===

[[File:Experiment Pasteur English.jpg|thumb|upright=1.2|[[Louis Pasteur]]'s 1859 experiment showed that a boiled nutrient broth did not give rise spontaneously to new life, but that if direct access to air was permitted, the broth decomposed, implying that small organisms (in modern terms, [[Endospore|microbial spores]]) had fallen in and started to grow in the broth.<ref name="Ball"/><ref name="TyndallFragments2"/> ]]

[[Louis Pasteur]]'s  experiment's in the late 1850's are widely seen as having settled the question of spontaneous generation.<ref>{{Cite web |url=https://www.immunology.org/pasteurs-col-de-cygnet-1859 |title=Pasteur's "col de cygnet" (1859) |website=www.immunology.org |publisher=[[British Society for Immunology]] |archive-url=https://web.archive.org/web/20190811175656/https://www.immunology.org/pasteurs-col-de-cygnet-1859 |access-date=August 11, 2019 |archive-date=11 August 2019 }}</ref> He boiled a meat broth in a [[swan neck flask]]; the bend in the neck of the flask prevented falling particles from reaching the broth, while still allowing the free flow of air. The flask remained free of growth for an extended period. When the flask was turned so that particles could fall down the bends, the broth quickly became clouded.<ref name="slowdeath" /> However, minority objections were persistent and not always unreasonable, given that the experimental difficulties were far more challenging than the popular accounts suggest. The investigations of the Irish physician [[John Tyndall]], a correspondent of Pasteur and an admirer of his work, were decisive in disproving spontaneous generation. All the same, Tyndall encountered difficulties in dealing with [[Endospore|microbial spores]], which were not well understood in his day. Like Pasteur, he boiled his [[microbiological culture|cultures]] to sterilize them, and some types of bacterial spores can survive boiling. The [[autoclave]], which eventually came into universal application in medical practice and microbiology to sterilise equipment, was introduced after these experiments.<ref name= "TyndallFragments2">{{cite book |last=Tyndall |first=John |author-link=John Tyndall |title=Fragments of Science |volume=2 |chapter=IV, XII, XIII |orig-year=1876–1878 |publisher=P. F. Collier |location=New York |date=1905 |url=https://archive.org/details/fragmenoscien02tyndrich }}</ref>

In 1862, the [[French Academy of Sciences]] paid special attention to the issue, establishing a prize "to him who by well-conducted experiments throws new light on the question of the so-called spontaneous generation" and appointed a commission to judge the winner.<ref>{{cite book |last1=Engelhardt |first1=Hugo Tristram |last2=Caplan |first2=Arthur L. |title=Scientific Controversies: Case Studies in the Resolution and Closure of Disputes in Science and Technology |url=https://books.google.com/books?id=6nkSX63VsLkC&pg=PA107 |year=1987 |publisher=Cambridge University Press |isbn=978-0-521-27560-6 |page=107}}</ref> Pasteur and others used the term ''biogenesis'' as the opposite of spontaneous generation, to mean that life was generated only from other life. Pasteur's claim followed the German physician [[Rudolf Virchow]]'s doctrine ''Omnis cellula e cellula'' ("all cells from cells"),<ref>{{cite book |last=Virchow |first=Rudolf |author-link=Rudolf Virchow |title=Die Cellularpathologie |language=de |trans-title=Cell Pathology |publisher=August Hirschwald |year=1859 |location=Berlin |url =https://archive.org/details/diecellularpatho00virc/ }}</ref> itself derived from the work of [[Robert Remak]].<ref>{{cite journal |last=Remak |first=Robert |date=1852 |title=Über extracellulare Entstehung thierischer Zellen und über Vermehrung derselben durch Theilung |language=de |trans-title=On the extracellular origin of animal cells, and their multiplication by division |journal=Archiv für Anatomie, Physiologie und Wissenschaftliche Medicin |volume=19 |pages=47–57}}</ref><ref name="slowdeath"/> After Pasteur's 1859 experiment, the term "spontaneous generation" fell out of favor. Experimentalists used a variety of terms for the study of the origin of life from nonliving materials. ''Heterogenesis'' was applied to the generation of living things from once-living organic matter (such as boiled broths), and the English physiologist [[Henry Charlton Bastian]] proposed the term ''archebiosis'' for life originating from non-living materials. Disliking the randomness and unpredictability implied by the term ''spontaneous generation'', in 1870 Bastian coined the term ''biogenesis'' for the formation of life from nonliving matter. Soon thereafter, however, the English biologist [[Thomas Henry Huxley]] proposed the term ''abiogenesis'' for this same process, and adopted ''biogenesis'' for the process by which life arises from existing life.<ref>{{cite book |last=Strick |first=James |title=Evolution & The Spontaneous Generation |chapter-url=https://books.google.com/books?id=yjKplNQv9zoC&pg=PR11 |access-date=August 27, 2012 |date= 2001 |publisher=Continuum International Publishing Group |isbn=978-1-85506-872-8 |pages=xi–xxiv |chapter=Introduction}}</ref>

==See also==

* [[Bugonia]]
* [[Barnacle goose myth]]
* [[Origin of life]]

==References==
{{Reflist}}
{{History of biology}}
{{Origin of life}}
{{Authority control}}

{{DEFAULTSORT:Spontaneous Generation}}
[[Category:Obsolete biology theories]]
[[Category:Origin of life]]
[[Category:Biological hypotheses]]

[[el:Αβιογένεση#Αυτόματη γένεση]]