EVOLUTIONARY THOUGHT BEFORE DARWIN
CONTENTS
CULTURAL TRADITIONS
SCHOOLS OF THOUGHT
MATERIALIST SCHOOL
CLASSICAL SCHOOL
NATIONAL SCHOOLS
JAMES HUTTON & UNIFORMITARIANISM
GEORGES CUVIER & CATASTROPHISM
CHARLES LYELL & UNIFORMITARIANISM
MAJOR IMPACTS ON DARWIN'S THINKING
SUMMARY: IDEAS IN DARWIN'S TIME
CULTURAL TRADITIONS
The intellectuals and naturalists who have considered evolution through the ages have been influenced by the philosophical movements through history.
Materialism emphasizes the physical world and is the philosophy that matter is the only thing in the universe which has reality. Matter is, therefore, the basis of all that exists. For example, materialism holds that all mental processes are caused by physical changes in the body and nervous system; materialists deny the existence of mind or soul which is distinct from matter.
Classicism stressed order, balance and simplicity in life -- in addition to reason, logic and analysis -- in seeking that which is universally true, beautiful and good. Classical movements in the west occured first in ancient Greece (reaching its height in 400's - 300's BC) and continued into the 1600's - 1700's in western Europe.
Romanticism stressed imagination, inspiration and emotion (passion) in seeking the exceptional and unconventional. The romantic movement occurred in the 1700's - mid 1800's. Romanticism contrasts with classicism, and often was a revolt against classicism.
SCHOOLS OF THOUGHT
Ideas about evolution existed long before Charles Darwin even appeared on the face of the Earth. Prior to Darwin's treatise, On The Origin of Species ..., there were several schools of thought regarding evolution. We will consider the schools and their philosophical views in chronological order to understand the major philosophical views leading up to Darwin's publication of On The Origin of Species ....
MATERIALIST SCHOOL
The Materialist School began more than 2000 years before Darwin with Thales (640? - 546? BC), who was the founder of Greek philosophy. It was concerned with material change, and produced first ideas about processes of evolution. For example,
Empedocles' (495? - 435? BC) ideas presaged the concept of adaptation.
Lucretius (94? - 55? BC) was a Roman poet who formalized materialist views in De Rerum Natura ("On the nature of things", circa 55 BC): He apparently had a general understanding of the fundamental aspects of natural selection and adaptation, but he did not understand the mechanism. He also believed in extinction.
CLASSICAL SCHOOL OF THOUGHT
Eclipsed Materialist Tradition 3-4 BC, but demise of Materialist School did not occur till about 1 BC.
Emphasized final, static perfection in organisms.
Complex school of thought comprising many ideas contributed by a number of well known philosophers and naturalists over about 2,000 years.
Two important ideas: Fixity of Species and Scala Naturae.
Fixity of Species
Fixity of Species -- concept that each species remains unchanged indefinately after its creation. Species were viewed as discrete, fixed entities which were sharply distinguished from other species and invariable. This concept was consistent with the views of catastrophists, creationists, and progressionists.
Plato (427?-347 BC): Theory of Forms (Theory of Ideas)
Two worlds: 1) perfect world of Forms and 2) imperfect world. Eidos is the eternal, perfect, heavenly embodiment of things. Variation in living and non-living things are imperfect manifestations of perfect world of Forms, and as such are not important.
Aristotle (384-322 BC): Theory of Types, application of Plato's Theory of Forms to biology.
Species reflect existence of unchanging, ideal form, the "universal" or "type", and variation represents an imperfect manifestation of underlying type. Hence, variation was not all that important--just "noise".
Carl Linnaeus (Swedish botanist, 1707-1778)
His work represents best of Classical Tradition.Father of Taxonomy, wrote Systema Naturae ("Natural System") and established binomial nomenclature.
Views were decidedly classicist; each species was immutable creation of God, which reflected an unchanging heavenly type. He believed that an entire species could be represented by one type specimen (holotype). This view of species is now referred to as the Typological Concept of Species. It stressed the constancy and discreteness of species, which were considered to be invariable and sharply different. Systematists of today designate types (e.g., holotypes) when describing species today as a vestige of this view of species.
These ideas of Plato, Aristotle and Linneaus are referred to as the concept of the fixity of species. Under this concept, species are viewed as fixed, unchanging entities. Once species originated (were created) they were believed not to change. These views are entirely at variance with Darwin's views as he considered individual variation to be of great importance and believed that species changed through time, resulting in transmutation (nowadays speciation).
Scala Naturae ("Scale of Nature")
Another concept of Aristotle.All creatures arranged on fixed, unchanging linear scale (hierarchy) of nature from lowest to highest forms, representing degrees of perfection. This idea also is called the chain of being, scale of being, or ladder of perfection: involved greater degrees of perfection of species with humans on top.
Later in 1600-1700's, Lamarck modified the idea of scala naturae from a fixed scale of perfection into continuous moving scale of progress, e.g. stair vs. escalator.
This idea too is entirely contrary to Darwin's views as he envisioned that descent with modification would result in branching evolutionary patterns. Moreover, distinguishing among higher or lower forms of life or degrees of perfection was not part of Darwin's theory.
DEMISE OF CLASSICAL SCHOOL
A diverse mix of factors eventually led to the demise of the Classical School which dominated thought for a very long period of time. Environmenatlism was perhaps the most important factor in bringing the Classical School to its end.
EnvironmentalismEnvironmental determinism: environmental determination of traits; environmental influences on behavior (migration).
Although not limited to France, it florished there.
ADAPTATION was a focus of Environmentalist School, especially in 19th century: various mechanisms proposed.
Climate was considered a major factor of the environment. For example, Buffon noted that animals were suited to their environments and viewed them to be the products of the climate they experienced.
The eventual failure of the Environmentalist School was its inability to explain the mechanism for the effect of the environment in determining traits.
Etienne Geoffroy Saint-Hillaire (Fr., 1772-1844)
All adaptations are directly induced by environment and passed on to offspring; focused on influences of temperature in producing adaptations.
Jean Baptiste de Lamarck (1744-1829)
Philosophie Zoologique (1809): presented theory of evolution.Believed in scala naturae but turned it into continuous, moving scale of progress toward perfect form versus the static scale of perfection.
Emphasized continuity of living organisms: species progressed up escalator from spontaneous generation to pinnacle with man at top through a process of transformation of one species into another.
Believed in evolution (transmutation of species); oddly did not believe in extinction.
Adaptations originated through the use of an organ as a result of an animal's own volition in responding to adverse, unfavorable environmental conditions. Acquired traits were passed onto offspring if present in each adult of a mating pair.
Inheritance of acquired characteristics was not new to him.
Charles Lyell (see below) spent great deal of effort refuting Lamarck's ideas (Burkhardt, 1984), and in the process, formulated the species problem that Darwin solved (Hull, 1984).
NATIONAL SCHOOLS
In the early 1800s, a number of national schools, each with its own traditions, arose and replaced the Classical School of thought. The separate schools of thought were the result of political turmoil which limited the exchange of ideas among scientists. There were three main schools of thought:
France -- Environmentalist School: Environmentalism
England -- Natural Theology
Emphasized purposeful design in nature.Teleology - structure determined by functional results. Explanation of phenomena/processes by purposes (goals, ends) they serve; purposeful determination by future goals.
"Argument from design" -- design in nature is evidence of benevolence, omnipotence, and existence of God as Creator of the existing order -- formalized by Thomas Aquinas.
Rev. William Paley (1743-1805; 1802: Natural Theology, or Evidences of the Existence and Attributes of the Deity): The foremost book of this school, which was widely read at Cambridge including by Darwin. Many examples Paley provided for his arguments also were used by Darwin because they were cases of remarkable adaptation.
Germany -- Naturphilosophie
Romantic school: "Bauplan" -- central concept of writers who emphasized the "unity of Creation" with little emphasis on adaptations of individual species. Bauplan is a common structural plan of life, e.g. skeleton of vertebrates built on similar plan.
CONTRIBUTIONS OF GEOLOGY
Advances in geology near the end of the 18th century and in the early 1800s made a number of contributions to our understanding of the Earth's history and to Darwin's ideas.
Geology initially was tied closely to cosmology which addressed the nature and origin of the universe and was linked to biblical teachings. For example, John Ussher (Irish, 1581-1656) was the first to propose age of Earth in years by using the Bible to add up the years. He concluded the Earth was created in 4004 BC.
Three major areas of debate in geology were:
James Hutton (Scottish, 1726-1797) &
UNIFORMITARIANISM
FOUNDER OF UNIFORMITARIANISM
First published ideas in Theory of the Earth (1788)
Contrast to views of catastrophism.CATASTROPHISM
Related to arguments over age of the Earth.Current rates of geological change rejected as having existed throughout all time, allowing argument that Earth is young, not old.
Earth's features, including the stratigraphic ones, were postulated to have resulted from extensive, rapid, violent changes (catastrophies), which were interspersed with long periods of little change.
Catastrophists argued for a young Earth because rates of change had been much greater in earlier periods.
UNIFORMITARIANISM
Counter to "mosaic geology," catastrophism, and progressionism. (Mosaic geology is the account of Creation in Genesis.)Rates of geological change are constant through time and extremely slow, requiring incredible time spans to effect changes. Thus, held that the Earth was old.
Observations of stream erosion convinced Hutton of extremely slow geological processes, requiring a very old Earth to complete them as processes occured at same rates in the past as in the present day.
Georges Cuvier (Fr., 1769-1832) & CATASTROPHISM
A paleontologist, founder of comparative anatomy, and forceful proponent of catastrophism--despite his studies of anatomy of fossils which led him to believe in both order and close relationships between living and dead organisms (unity of nature vs. the pandemonium expected in fossil record associated with catastrophism).He did not believe in evolution, but he believed in the reality of fossils and possibility of extinction. Along with others, he established the reality of fossils. Thus, his own theory of the Earth's history had to account for both the existence of fossils and the occurrence of extinction.
His theory: The Earth's history was a series of cataclysmic events, with each stratum laid down by a catastrophic flood or earth quake. In each catastrophe, all life of the period was destroyed and buried in a new stratum as God destroyed and recreated each of the four major types (phyla) of animals he recognized (Radiata, Mollusca, Articulata, Vertebrata). God did this because not satisfied with prior creation and made a better one.
PROGRESSIONISM -- belief in successively better creations. After each cataclysmic episode, each new creation brought an improvement over the previous one and all such creations were based on a "Divine Plan," as manifested in the unity of nature. There was a progression from simple to complex forms of life through geological time. This idea meshed well with Cuvier's findings and the ideas of catastrophism and creationism.
His theory was contrary to the scala naturae by recognizing four different branches of the animal kingdom which could not be arranged on a single hierarchy (hierarchies possible within). The rejection of the single hierarchy led to the demise of the classicist school.
Charles Lyell (Scottish, 1797-1875) & UNIFORMITARIANISM
Principles of Geology (Vol. 1, 1830; Vol. 2, 1832) had a significant influence on Charles Darwin's thinking. Darwin had copy of Principles of Geology (1830) with him on Beagle (1831).Responsible for change from CATASTROPHISM to UNIFOMITARIANISM.
Lyell's arguments for UNIFORMITARIANISM:
- Natural laws do not vary through time.
- Geological features were created by processes we now see operating, i.e. the same forces at work today shaped the Earth in the past. Thus, present-day events are a key to the past and can be used to infer past events.
- Rates of geological processes did not vary with time (no longer believed). Hence, cataclysmic explanations were not necessary.
NONPROGRESSIONISM
Lyell's theory that there could be no progress or overall change under conditions of uniformitarianism. Contrary to Cuvier's theory: there could be no successive series of creations. Contrary to Lamarck's theory: there could be no transformation of one species into another.
Lyell initially did not believe in evolution. He attacked Lamarck for belief in evolution and also for denial of extinction. In Volume 2 of Principles of Geology, he used ideas we now know as stabilizing (normalizing) selection to argue against evolution. He initially criticized Darwin, but later accepted Darwinism in last few editions of Principles of Geology.
Vestiges of the Natural History of Creation
Robert Chambers (1802-1871) Wrote Vestiges of the Natural History of Creation anonymously in 1844.
The book addressed main scientific issues of the period, including a well-written explication of a scientific theory of origin and subsequent evolution of life on Earth. It was read carefully by Darwin, who had formulated his theory of transmutation about 1838.
The book drew strong, vigorous criticism, perhaps decreasing some later anti-Darwinian attacks. The criticisms also may have caused Darwin to wait more than ten years to publish his theory. They also may have caused Darwin to present his arguments in moderate, well-reasoned prose.
MAJOR IMPACTS ON DARWIN'S THINKING [chronological order; BE, p.26-32]
- Lyell: Principles of Geology, volume 1 (1830) -- uniformitarianism, see above
- Voyage of Beagle
- St. Jago, Cape Verde Archipelago: possibly convinced Darwin about uniformitarianism.
- Pampas near Montevideo: fossils.
- Galapagos Islands: most important area -- animals, especially Darwin's finches which showed gradation and diversity of structure suggestive of one species radiating into many.
- Malthus: An Essay on the Principle of Population
Read by Darwin in October, 1838, about the time he formulated the theory of transmutation. Before reading Malthus, Darwin believed in the natural theological idea of perfect adaptation. Darwin shifted to the ideas of relative adaptation and the principle of divergence after reading Malthus. Many biographers believe this change occurred about 1838, but Ospovot (1981) has argued that Darwin continued to believe in perfect adaptation in the same way as his contemporaries did until 1854. Ospovot questions the nearly 20-year delay (1838-1854) in this transition and suggests it was either fear of ostracism or that Darwin was still working on his ideas. Ideas of perfect adaptation and harmony in nature were linked in the minds of natural theologists. Relative adaptation meant that natural selection was operating continuously.
SUMMARY: IDEAS IN DARWIN'S TIME
When Darwin wrote On the Origin of Species..., the prevailing, orthodox view of species was that they were non-changing entities (species fixity). Darwin's claim that species evolved into other species then was immediately controversial.
Other writers in Darwin's time and before (including his grandfather) had questioned the idea of species fixity. These ideas primarily addressed the possibility that species may change into other species, but Darwin's theory explained the mechanism (how, why) for species change and, in doing so, explained their evolution into other species.
Jean-Baptiste Lamarck (Philosophie Zoologique) was the most influential of the pre-Darwinian authors to argue that species change over time. Lamarck's and Darwin's ideas were very different. Lamarck considered the "transformation" (historians' usage) of species lineages which indefinitely changed from one form into another and did not become extinct (vs. Darwin). The lineages did not branch, as did Darwin's.
Two mechanisms were used to explain the transformation. The first was that some unknown, internal force/mechanism would cause an organism to produce offspring which were slightly different from itself. Accumulation of these changes would then lead to the transformation of a new species.The second mechanism was the inheritance of acquired characters ("Lamarckian inheritance"), which was not new to Lamarck (ancient idea extending back to Plato) and erroneously attributed to Lamarck (as the essence of his theory) by Weismann (Germplasm Theory). During the development of an organism, it acquired characteristics as a result of exercise. Species could be transformed through the inheritance of individually acquired characteristics. Volition ("striving", "wishing", "willing") of the organism has been attributed to his theory. But some authors contend that volition is not a requirement of the theory. Instead, there must be flexibility in development coupled with the inheritance of acquired characters.
Cuvier was Lamarck's primary antagonist. Cuvier's responses to Lamarck helped to establish in the minds of biologists the idea that species were fixed, unchanging entities. Cuvier and his associates (school) studied the anatomy of animals to discover the fundamental, fixed plans by which they were designed. Cuvier also established that extinction does occur.Cuvier believed each species had a separate origin and remained an unchanging, fixed form until it became extinct. This fixity of species was the prevailing view at the time Darwin's work appeared. Catastrophism and Cuvier's idea of progressionism also were popular views of the time.