Aristotle

=== Biology ===
{{Main|Aristotle's biology}}
[[File:Tremoctopus violaceus5.jpg| thumb | upright | Among many pioneering zoological observations, Aristotle described the reproductive [[hectocotylus|hectocotyl arm]] of the [[octopus]] (bottom left).]]

==== Empirical research ====
Aristotle was the first person to study biology systematically,{{sfn| Leroi | 2015 | page=7}} and biology forms a large part of his writings. He spent two years observing and describing the zoology of [[Lesbos]] and the surrounding seas, including in particular the Pyrrha lagoon in the centre of Lesbos.{{sfn| Leroi | 2015 | page=14}}{{sfn| Thompson | 1910 | page=Prefatory Note}} His data in ''[[History of Animals]]'', ''[[Generation of Animals]]'', ''[[Movement of Animals]]'', and ''[[Parts of Animals]]'' are assembled from his own observations,<ref>{{Cite web|url=https://www.independent.co.uk/arts-entertainment/books/reviews/darwins-ghosts-by-rebecca-stott-7808310.html|title=Darwin's Ghosts, By Rebecca Stott
|website=independent.co.uk|date=2 June 2012
|access-date=19 June 2012}}</ref> statements given by people with specialized knowledge, such as beekeepers and fishermen, and less accurate accounts provided by travellers from overseas.{{sfn| Leroi | 2015 | pages=196, 248}} His apparent emphasis on animals rather than plants is a historical accident: his works on [[botany]] have been lost, but two books on plants by his pupil Theophrastus have survived.{{sfn| Day | 2013 | pp=5805–5816}}

Aristotle reports on the sea-life visible from observation on Lesbos and the catches of fishermen. He describes the [[catfish]], [[electric ray]], and [[frogfish]] in detail, as well as [[cephalopod]]s such as the [[octopus]] and [[paper nautilus]]. His description of the [[hectocotylus|hectocotyl arm]] of cephalopods, used in sexual reproduction, was widely disbelieved until the 19th century.{{sfn| Leroi | 2015 | pages=66–74, 137}} He gives accurate descriptions of the four-chambered fore-stomachs of [[ruminant]]s,{{sfn| Leroi | 2015 | pages=118–119}} and of the [[Ovoviviparity|ovoviviparous]] embryological development of the [[hound shark]].{{sfn| Leroi | 2015 | page=73}}

He notes that an animal's structure is well matched to function so birds like the [[heron]] (which live in marshes with soft mud and live by catching fish) have a long neck, long legs, and a sharp spear-like beak, whereas [[duck]]s that swim have short legs and webbed feet.{{sfn| Leroi | 2015 | pages=135–136}} [[Charles Darwin|Darwin]], too, noted these sorts of differences between similar kinds of animal, but unlike Aristotle used the data to come to the theory of [[evolution]].{{sfn| Leroi | 2015 | page=206}} Aristotle's writings can seem to modern readers close to implying evolution, but while Aristotle was aware that new mutations or [[Hybridisation (biology)|hybridizations]] could occur, he saw these as rare accidents. For Aristotle, accidents, like heat waves in winter, must be considered distinct from natural causes. He was thus critical of Empedocles's materialist theory of a "survival of the fittest" origin of living things and their organs, and ridiculed the idea that accidents could lead to orderly results.{{sfn| Sedley | 2007 | page=189}} To put his views into modern terms, he nowhere says that different species can have a [[common descent|common ancestor]], or that one kind can [[speciation|change into another]], or that kinds can become [[extinction|extinct]].{{sfn| Leroi | 2015 | page=273}}

==== Scientific style ====
[[File:Two of Aristotle's Growth Laws.svg| thumb | left | upright=1.4 | Aristotle inferred growth laws from his observations on animals, including that [[brood size]] decreases with body mass, whereas [[gestation]] period increases. He was correct in these predictions, at least for mammals: data are shown for mouse and elephant.]]

Aristotle did not do experiments in the modern sense.{{sfn| Taylor | 1922 | page=42}} He used the ancient Greek term ''pepeiramenoi'' to mean observations, or at most investigative procedures like dissection.{{sfn| Leroi | 2015 | pages=361–365}} In ''Generation of Animals'', he finds a fertilized hen's egg of a suitable stage and opens it to see the embryo's heart beating inside.{{sfn| Leroi | 2011}}{{sfn| Leroi | 2015 | pages=197–200}}

Instead, he practiced a different style of science: systematically gathering data, discovering patterns common to whole groups of animals, and inferring possible causal explanations from these.{{sfn| Leroi | 2015 | pages=365–368}}{{sfn| Taylor | 1922 | page=49}} This style is common in modern biology when large amounts of data become available in a new field, such as [[genomics]]. It does not result in the same certainty as experimental science, but it sets out testable hypotheses and constructs a narrative explanation of what is observed. In this sense, [[Aristotle's biology]] is scientific.{{sfn| Leroi | 2015 | pages=365–368}}

From the data he collected and documented, Aristotle inferred quite a number of [[biological rules|rules]] relating the life-history features of the live-bearing tetrapods (terrestrial placental mammals) that he studied. Among these correct predictions are the following. Brood size decreases with (adult) body mass, so that an elephant has fewer young (usually just one) per brood than a mouse. [[Life expectancy|Lifespan]] increases with [[gestation period]], and also with body mass, so that elephants live longer than mice, have a longer period of gestation, and are heavier. As a final example, [[fecundity]] decreases with lifespan, so long-lived kinds like elephants have fewer young in total than short-lived kinds like mice.{{sfn| Leroi | 2015 | page=408}}{{Clear}}

==== Classification of living things ====

{{further|Scala naturae}}

[[File:Scyliorhinus retifer embryo.JPG|thumb |Aristotle recorded that the [[embryo]] of [[Mustelus canis|<!--a different species shown-->a dogfish]] was attached by a cord to a kind of placenta (the [[yolk sac]]), like a higher animal; this formed an exception to the linear scale from highest to lowest.{{sfn|Leroi|2015|pages=72–74}}]]

Aristotle distinguished about 500 species of [[animal]]s,{{sfn|Bergstrom|Dugatkin|2012|page=35}}{{sfn|Rhodes|1974|page=7}} arranging these in the ''History of Animals'' in a graded scale of perfection, a nonreligious version of the ''[[scala naturae]]'', with man at the top. His system had eleven grades of animal, from highest potential to lowest, expressed in their form at birth: the highest gave [[viviparity|live birth]] to hot and wet creatures, the lowest laid cold, dry mineral-like eggs. Animals came above [[plant]]s, and these in turn were above minerals.{{sfn|Mayr|1982|pages=201–202}}{{sfn|Lovejoy|1976}} He grouped what the modern zoologist would call [[vertebrate]]s as the hotter "animals with blood", and below them the colder [[invertebrate]]s as "animals without blood". Those with blood were divided into the live-bearing ([[mammal]]s), and the egg-laying ([[bird]]s, [[reptile]]s, [[fish]]). Those without blood were insects, crustacea (non-shelled – cephalopods, and [[crustacea|shelled]]) and the hard-shelled [[mollusc]]s ([[bivalve]]s and [[gastropod]]s). He recognised that animals did not exactly fit into a linear scale, and noted various exceptions, such as that sharks had a [[placenta]] like the tetrapods. To a modern biologist, the explanation, not available to Aristotle,<!--Leroi |p= 113--> is [[convergent evolution]].{{sfn|Leroi|2015|pages=111–119}} Philosophers of science have generally concluded that Aristotle was not interested in taxonomy,<ref>{{cite book |last=Lennox |first=James G. |title=Aristotle's Philosophy of Biology: Studies in the Origins of Life Science |date=2001 |publisher=[[Cambridge University Press]] |location=Cambridge |isbn=0-521-65976-0 |pages=346}}</ref><ref>{{cite journal |last1=Sandford |first1=Stella |title=From Aristotle to Contemporary Biological Classification: What Kind of Category is "Sex"? |journal=Redescriptions: Political Thought, Conceptual History and Feminist Theory |date=3 December 2019 |volume=22 |issue=1 |pages=4–17 |doi=10.33134/rds.314 |s2cid=210140121 |language=en |issn=2308-0914|doi-access=free }}</ref> but zoologists who studied this question in the early 21st century think otherwise.<ref>{{cite journal |last1=Voultsiadou |first1=Eleni |last2=Vafidis |first2=Dimitris |title=Marine invertebrate diversity in Aristotle's zoology |journal=Contributions to Zoology |date=1 January 2007 |volume=76 |issue=2 |pages=103–120 |doi=10.1163/18759866-07602004 |s2cid=55152069 |url=https://doi.org/10.1163/18759866-07602004 |language=en |issn=1875-9866}}</ref><ref>{{cite journal |last1=von Lieven |first1=Alexander Fürst |last2=Humar |first2=Marcel |title=A Cladistic Analysis of Aristotle's Animal Groups in the "Historia animalium" |journal=History and Philosophy of the Life Sciences |date=2008 |volume=30 |issue=2 |pages=227–262 |jstor=23334371 |pmid=19203017 |url=https://www.jstor.org/stable/23334371 |issn=0391-9714}}</ref><ref>{{cite journal |last1=Laurin |first1=Michel |last2=Humar |first2=Marcel |title=Phylogenetic signal in characters from Aristotle's History of Animals |journal=Comptes Rendus Palevol |date=2022 |volume=21 |issue=1 |pages=1–16 |doi=10.5852/cr-palevol2022v21a1 |s2cid=245863171 |language=fr|doi-access=free }}</ref> He believed that purposive final causes guided all natural processes; this [[teleological]] view justified his observed data as an expression of formal design.{{sfn|Mason|1979|pp=43–44}}

{|class="wikitable" style="font-size: 80%;"
|+ Aristotle's ''[[Scala naturae]]'' (highest to lowest)
! Group !! Examples<br/>(given by Aristotle) !! Blood !! Legs !! Souls<br/>(Rational,<br/>Sensitive,<br/>Vegetative) !! Qualities<br/>({{font color|red|Hot}}–{{font color|blue|Cold}},<br/>{{font color|green|Wet}}–{{font color|brown|Dry}})
|-
|Man||Man||with&nbsp;blood||2 legs||R, S, V||{{font color|red|Hot}}, {{font color|green|Wet}}
|-
|[[Mammal|Live-bearing tetrapods]]||Cat, [[hare]]||with&nbsp;blood||4 legs||S, V||{{font color|red|Hot}}, {{font color|green|Wet}}
|-
|[[Cetaceans]]||[[Dolphin]], [[whale]]||with&nbsp;blood||none||S, V||{{font color|red|Hot}}, {{font color|green|Wet}}
|-
|[[Birds]]||[[Bee-eater]], [[nightjar]]||with&nbsp;blood||2 legs||S, V||{{font color|red|Hot}}, {{font color|green|Wet}}, except {{font color|brown|Dry}} eggs
|-
|[[Reptile|Egg-laying tetrapods]]||[[Chameleon]], [[crocodile]]||with&nbsp;blood||4 legs||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}} except scales, eggs
|-
|[[Snakes]]||Water snake, [[Ottoman viper]]||with&nbsp;blood||none||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}} except scales, eggs
|-
|Egg-laying [[fish]]es||[[Sea bass]], [[Sparisoma cretense|parrotfish]]||with&nbsp;blood||none||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}}, including eggs
|-
|(Among the egg-laying fishes):<br />placental [[selachian]]s||[[Shark]], [[Skate (fish)|skate]]||with&nbsp;blood||none||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}}, but [[placenta]] like tetrapods
|-
|[[Crustaceans]]||[[Shrimp]], [[crab]]||without||many legs||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}} except shell
|-
|[[Cephalopods]]||[[Squid]], [[octopus]]||without||tentacles||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}}
|-
|[[Mollusc|Hard-shelled animals]]||[[Cockle (bivalve)|Cockle]], [[Charonia variegata|trumpet snail]]||without||none||S, V||{{font color|blue|Cold}}, {{font color|brown|Dry}} (mineral shell)
|-
|Larva-bearing insects||[[Ant]], [[cicada]]||without||6 legs||S, V||{{font color|blue|Cold}}, {{font color|brown|Dry}}
|-
|[[Spontaneous generation|Spontaneously generating]]||[[Sponges]], [[worm]]s||without||none||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}} or {{font color|brown|Dry}}, from earth
|-
|[[Plants]]||[[Common fig|Fig]]||without||none||V||{{font color|blue|Cold}}, {{font color|brown|Dry}}
|-
|[[Mineral]]s||Iron||without||none||none||{{font color|blue|Cold}}, {{font color|brown|Dry}}
|}