Thehistory of zoology beforeCharles Darwin's 1859 theory ofevolution traces the organized study of theanimal kingdom fromancient tomodern times. Although the concept ofzoology as a single coherent field arose much later, systematic study of zoology is seen in the works ofAristotle andGalen in the ancientGreco-Roman world. This work was developed in the Middle Ages byIslamic medicine and scholarship, and their work was in turn extended by European scholars such asAlbertus Magnus.

During the EuropeanRenaissance and early modern period, zoological thought was revolutionized in Europe by a renewed interest inempiricism and the discovery of many novel organisms. Prominent in this movement were the anatomistVesalius and the physiologistWilliam Harvey, who used experimentation and careful observation, and naturalists such asCarl Linnaeus andBuffon who began toclassify the diversity of life and thefossil record, as well as the development and behavior of organisms.Microscopy revealed the previously unknown world of microorganisms, paving the way forcell theory. The growing importance ofnatural theology, partly a response to the rise ofmechanical philosophy, encouraged the growth of natural history (although it entrenched theargument from design).

Over the 18th and 19th centuries, zoology became an increasingly professionalscientific discipline. Explorer-naturalists such asAlexander von Humboldt investigated the interaction between organisms and their environment, and the ways this relationship depends on geography—laying the foundations forbiogeography,ecology andethology. Naturalists began to rejectessentialism and consider the importance ofextinction and themutability of species.Cell theory provided a new perspective on the fundamental basis of life. These developments, as well as the results fromembryology andpaleontology, were synthesized inCharles Darwin's theory ofevolution bynatural selection. In 1859, Darwin placed the theory of organic evolution on new footing through his discovery of a process by which it could occur, and observational evidence suggesting that it had done so.

Theearliest humans must have gathered and transmitted knowledge aboutanimals to increase their chances of survival. This may have included unsystematic knowledge of human and animal anatomy and aspects of animal behavior (such as migration patterns). With theNeolithic Revolution (about 10,000 years ago), humansdomesticated animals, and in civilizations such as those ofancient Egypt,pastoralism and farming emerged as alternatives to thehunter-gatherer lifestyle.^[1]

The ancient cultures ofMesopotamia, theIndian subcontinent, andChina, among others, produced renowned surgeons and students of the natural sciences such asSusruta andZhang Zhongjing, reflecting sophisticated and independent systems of natural philosophy. Taoist philosophers, such asZhuangzi in the 4th century BC, expressed ideas related toevolution, such as denying the fixity of biological species and speculating that species had developed differing attributes in response to differing environments.^[2] The ancient IndianAyurveda tradition developed a theory of three humors, resembling but unrelated to thefour humors ofancient Greek medicine (and including further complications, such as the body being composed offive elements and seven basictissues). Ayurvedic writers also classified living things into four categories based on the way they were born (from the womb, from eggs, from seeds, or via heat and moisture) and explained the conception of afetus in detail. They also made considerable advances in the field ofsurgery, often without the use of humandissection or animalvivisection.^[3] One of the first known Ayurvedic treatises was theSushruta Samhita, attributed to Sushruta in the 6th century BC. It can be considered an early contribution to themateria medica genre, describing 700 medicinal plants, 64 preparations from mineral sources, and 57 preparations based on animal sources.^[4] Notwithstanding such developments, the roots of modern zoology are usually traced back to thesecular tradition ofancient Greek philosophy.^[5]

Thepre-Socratic philosophers asked many questions about life but produced little systematic knowledge of specifically zoological interest—though the attempts of theatomists to explain life in purely physical terms would recur periodically through the history of zoology. However, the medical theories ofHippocrates and his followers, especiallyhumorism, had a lasting impact.^[6]

The philosopherAristotle createdthe science of biology, basing its theory on both hismetaphysical principles and on observation. He proposed theories for the processes of metabolism, temperature regulation, information processing, embryonic development, and inheritance. He made detailed observations of nature, especially the habits andattributes ofanimals in the sea atLesbos. He classified 540 animal species, and dissected at least 50.^[7][8][9]

Aristotle, and nearly all Western scholars after him until the 18th century, believed that creatures were arranged in a graded scale of perfection rising from plants on up to humans: thescala naturae orGreat Chain of Being.^[10]

A few scholars in theHellenistic period under thePtolemies—particularlyHerophilus of Chalcedon andErasistratus of Chios—amended Aristotle's physiological work, even performing experimental dissections and vivisections.^[11]Claudius Galen became the most important authority on medicine and anatomy. Though a few ancientatomists such asLucretius challenged theteleological Aristotelian viewpoint that all aspects of life are the result of design or purpose, teleology (and after the rise ofChristianity,natural theology) remained central to biological thought until the 18th and 19th centuries.^[12]

The decline of theRoman Empire led to the disappearance or destruction of much knowledge, though physicians still incorporated many aspects of the Aristotelian tradition into training and practice. InByzantium and theIslamic world, many of Aristotle's works were translated intoArabic and commented upon by scholars such asAvicenna andAverroes.^[13]

MedievalMuslim physicians,scientists andphilosophers made significant contributions to zoological knowledge between the 8th and 13th centuries during theIslamic Golden Age. The Arab scholaral-Jahiz (781–869) described the idea of afood chain,^[14] and was an early adherent ofenvironmental determinism.^[15]

During theHigh Middle Ages, a few European scholars such asHildegard of Bingen,Albertus Magnus andFrederick II expanded the natural history canon. Magnus'sDe animalibus libri XXVI was one of the most extensive studies of zoological observation published before modern times.^[16][17]

TheRenaissance was the age of collectors and travellers, when many of the stories were actually demonstrated as true when the living or preserved specimens were brought to Europe. Verification by collecting of things, instead of the accumulation of anecdotes, then became more common, and scholars developed a new faculty of careful observation.^[18] The Renaissance brought expanded interest in both empirical natural history and physiology. In 1543,Andreas Vesalius inaugurated the modern era of Western medicine with his seminalhuman anatomy treatiseDe humani corporis fabrica, which was based on dissection of corpses. Vesalius was the first in a series of anatomists who gradually replacedscholasticism withempiricism in physiology and medicine, relying on first-hand experience rather than authority and abstract reasoning.Bestiaries—a genre that combines both the natural and figurative knowledge of animals—also became more sophisticated.Conrad Gessner's great zoological work,Historiae animalium, appeared in four volumes, 1551–1558, at Zürich, a fifth being issued in 1587. His works were the starting-point of modern zoology. Other major works were produced byWilliam Turner,Pierre Belon,Guillaume Rondelet, andUlisse Aldrovandi.^[19] Artists such asAlbrecht Dürer andLeonardo da Vinci, often working with naturalists, were also interested in the bodies of animals and humans, studying physiology in detail and contributing to the growth of anatomical knowledge.^[20]

In the 17th century, the enthusiasts of the new sciences, the investigators of nature by means of observation and experiment, banded themselves into academies or societies for mutual support and discourse. The first founded of surviving European academies, theAcademia Naturae Curiosorum (1651) especially confined itself to the description and illustration of the structure of plants and animals; eleven years later (1662) theRoyal Society of London was incorporated byroyal charter, having existed without a name or fixed organisation for seventeen years previously (from 1645). A little later theAcademy of Sciences ofParis was established byLouis XIV,^[18] later still theRoyal Society of Sciences in Uppsala was founded. Systematizing, naming and classifying dominated zoology throughout the 17th and 18th centuries.Carl Linnaeus published a basictaxonomy for the natural world in 1735 (variations of which have been in use ever since), and in the 1750s introducedscientific names for all his species.^[21] While Linnaeus conceived of species as unchanging parts of a designed hierarchy, the other great naturalist of the 18th century,Georges-Louis Leclerc, Comte de Buffon, treated species as artificial categories and living forms as malleable—even suggesting the possibility ofcommon descent. Though he was writing in an era before evolution was recognized, Buffon is a key figure in thehistory of evolutionary thought; his "transformist" theory would influence the evolutionary theories of bothJean-Baptiste Lamarck andCharles Darwin.^[22]

Before theAge of Exploration, naturalists had little idea of the sheer scale of biological diversity. The discovery and description of new species and the collection of specimens became a passion of scientific gentlemen and a lucrative enterprise for entrepreneurs; many naturalists traveled the globe in search of scientific knowledge and adventure.^[23]

Extending the work of Vesalius into experiments on still living bodies (of both humans and animals),William Harvey investigated the roles of blood, veins and arteries. Harvey'sDe motu cordis in 1628 was the beginning of the end for Galenic theory, and alongsideSantorio Santorio's studies of metabolism, it served as an influential model of quantitative approaches to physiology.^[24]

In the early 17th century, the micro-world of zoology was just beginning to open up. A few lensmakers and natural philosophers had been creating crudemicroscopes since the late 16th century, andRobert Hooke published the seminalMicrographia based on observations with his own compound microscope in 1665. But it was not untilAntony van Leeuwenhoek's dramatic improvements in lensmaking beginning in the 1670s—ultimately producing up to 200-fold magnification with a single lens—that scholars discoveredspermatozoa,bacteria,infusoria and the sheer strangeness and diversity of microscopic life. Similar investigations byJan Swammerdam led to new interest inentomology and built the basic techniques of microscopic dissection andstaining.^[25]

Debate over theflood described in the Bible catalyzed the development ofpaleontology; in 1669Nicholas Steno published an essay on how the remains of living organisms could be trapped in layers of sediment and mineralized to producefossils. Although Steno's ideas about fossilization were well known and much debated among natural philosophers, an organic origin for all fossils would not be accepted by all naturalists until the end of the 18th century due to philosophical and theological debate about issues such as the age of the earth andextinction.^[26]

Advances inmicroscopy also had a profound impact on biological thinking. In the early 19th century, a number of biologists pointed to the central importance of thecell. In 1838 and 1839,Schleiden andSchwann began promoting the ideas that (1) the basic unit of organisms is the cell and (2) that individual cells have all the characteristics oflife, though they opposed the idea that (3) all cells come from the division of other cells. Thanks to the work ofRobert Remak andRudolf Virchow, however, by the 1860s most biologists accepted all three tenets of what came to be known ascell theory.^[27]

Up through the 19th century, the scope of zoology was largely divided between physiology, which investigated questions of form and function, and natural history, which was concerned with the diversity of life and interactions among different forms of life and between life and non-life. By 1900, much of these domains overlapped, while natural history (and its counterpartnatural philosophy) had largely given way to more specialized scientific disciplines—cytology,bacteriology,morphology,embryology,geography, andgeology. Widespread travel by naturalists in the early-to-mid-19th century resulted in a wealth of new information about the diversity and distribution of living organisms. Of particular importance was the work ofAlexander von Humboldt, which analyzed the relationship between organisms and their environment (i.e., the domain ofnatural history) using the quantitative approaches ofnatural philosophy (i.e.,physics andchemistry). Humboldt's work laid the foundations ofbiogeography and inspired several generations of scientists.^[28]

The emerging discipline of geology also brought natural history and natural philosophy closer together;Georges Cuvier and others made great strides incomparative anatomy andpaleontology in the late 1790s and early 19th century. In a series of lectures and papers that made detailed comparisons between living mammals andfossil remains Cuvier was able to establish that the fossils were remains of species that had becomeextinct—rather than being remains of species still alive elsewhere in the world, as had been widely believed.^[29] Fossils discovered and described byGideon Mantell,William Buckland,Mary Anning, andRichard Owen among others helped establish that there had been an 'age of reptiles' that had preceded even the prehistoric mammals. These discoveries captured the public imagination and focused attention on the history of life on earth.^[30]

Charles Darwin, combining the biogeographical approach of Humboldt, the uniformitarian geology of Lyell,Thomas Malthus's writings on population growth, and his own morphological expertise, created a more successful evolutionary theory based onnatural selection; similar evidence ledAlfred Russel Wallace to independently reach the same conclusions.^[31]Charles Darwin's early interest in nature led him on afive-year voyage onHMS Beagle which established him as an eminentgeologist whose observations and theories supportedCharles Lyell'suniformitarian ideas, and publication of hisjournal of the voyage made him famous as a popular author.^[32] Puzzled by the geographical distribution of wildlife andfossils he collected on the voyage, Darwin investigated thetransmutation of species and conceived his theory of natural selection in 1838.^[33] Although he discussed his ideas with several naturalists, he needed time for extensive research and his geological work had priority.^[34] He was writing up his theory in 1858 whenAlfred Russel Wallace sent him an essay which described the same idea, prompting immediate joint publication ofboth of their theories.^[35]Darwin'sOn the Origin of Species, published on 24 November 1859, a seminal work of scientific literature, was to be the foundation of evolutionary biology.

• History of Zoology
• List of zoologists
• List of Russian zoologists
• Important Publications in Zoology
• Timeline of zoology

• Desmond, Adrian J.;Moore, James (1991).Darwin. Warner Books.

• History of zoology

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