History of evolutionary thought

1 Pre-Darwinian background

Anaximander 6th century BC

Empedocles 5th century BC

Plato 4th century BC

Aristotle 4th century BC

Pliny the Elder 1st century AD

Lactantius 3rd century AD

Greek philosophers

• Idealism

• Two coexisting worlds

Western Thought: Greek Philosophers Plato

Ideal, eternal, real world vs Imperfect world

-apparent to humans-all organisms perfectly -variation within adapted populations part of this

illusory world that our senses perceive

Anaximander 6th century BC

Empedocles 5th century BC

Plato 4th century BC

Aristotle 4th century BC

Pliny the Elder 1st century AD

Lactantius 3rd century AD

Greek philosophers

Scala Naturae - Great Chain of Being

•hierarchy and order in the natural world•order is a product of God’s creation•species are fixed entities•humans are the link between physical and spiritual

worlds

Western Thought: Greek PhilosophersAristotle

Aristotle’s Scale of Nature - Great Chain of Being

rocks

plants

animals

humans

angels

simple

complex

most perfect

most imperfect

Anaximander 6th century BC

Empedocles 5th century BC

Plato 4th century BC

Aristotle 4th century BC

Pliny the Elder 1st century AD

Lactantius 3rd century AD

Greek philosophers

St Thomas Aquinas (13th century) Summa Theologica:

Whatever lacks knowledge cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is directed by the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.

Western Thought: Judeo-Christian CultureThe School of Natural Theology

Adaptations of organisms reflect God’s design

Leibniz (1646-1716) – Natura non facit saltum

suggested gaps in the GCoB caused by some species being extinct

Western Thought: Judeo-Christian CultureThe School of Natural Theology

Fixity of species:

New spp had not appeared during recorded history

How then could individuals of a single spp be separated from others of the same kind and become transformed into a new spp?

Where are all the missing links between existing spp if transformation from one to the other has taken place?

Buffon (1707-1788)

Les espèces sont les seuls êtres de la nature

Buffon (1753) Natural History (4th vol)

Not only the ass and the horse, but also man, the apes, the quaduped, and all the animals, might be regarded as constituting but a single family…If it were admitted that the ass is of the family of the horse, and differs from the horse only because it has varied from the original form, one could equally well say that the ape is of the family of man, that he is degenerate man, that man and ape have a common origin; that, in fact, all the families, among plants as well as animals, have come from a single stock, and that all animal are descended from a single animal, from which have sprung in the course of time, as a result of progress or of degeneration, all the other races of animals.

Reverend William Paley in Natural Theology (1802)

“when we come to inspect the watch, we perceive. . . that its several parts are framed and put together for a purpose, e.g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point out the hour of the day; that if the different parts had been differently shaped from what they are, or placed after any other manner or in any other order than that in which they are placed, either no motion at all would have been carried on in the machine, or none which would have answered the use that is now served by it. . . . the inference we think is inevitable, that the watch must have had a maker -- that there must have existed, at some time and at some place or other, an artificer or artificers who formed it for the purpose which we find it actually to answer, who comprehended its construction and designed its use…”

Western ThoughtThe School of Natural Theology

Scientific advances that influenced Darwin

Carolus Linnaeus (1754): Reflections on the study of nature

If the Maker has furnished this globe, like a museum, with the most admirable proofs of his wisdom and power; if this splendid theater would be adorned in vain without a spectator; and if man the most perfect of all his works is alone capable of considering the wonderful economy of the whole; it follows that man is made for the purpose of studying the Creator’s work and that he may observe in them the evident marks of divine wisdom.

Scientific advances that influenced Darwin: Systematics: Linnaeus

Linnaeus - Father of Taxonomy

• Recognized species as the fundamental unit defined by reproduction

• Developed a system of categorizing species

– Binomial nomenclature

– Hierarchy of categories above genus

Two components of this view:

•Gradualism-profound change is the cumulative product of slow, continuous change (Hutton)

•Uniformitarianism-geological processes haven’t changed over the course of history (Lyell)

View leads to the conclusion:•Earth is very old!

Current geological processes that we observe today are responsible for all geologic features.

Scientific advances that influenced Darwin: Geology: Hutton and Lyell

Lamarck’s Theory of Evolution (1809)

•species originate by spontaneous generation

•“nervous fluid” causes species to progress down unique path

•no species go extinct

Scientific advances that influenced Darwin: Evolution: Lamarck

1. Use and Disuse of Organs2. Inheritance of Acquired Characteristics

The Mechanism for Lamarck’s Theory

Lamarck

First to suggest branching rather than linear tree

Malthus (1798): Essay on the Principle of Population

Scientific advances that influenced Darwin:Economics: Malthus

The rate of human population growth exceeds the the rate of increase in the food supply….leads to human famines.

More organisms are born than can survive.

Organisms compete with one another to survive.

Stratification-fossils were deposited in layers of different ages.

Change through time-older fossils were less similar to modern forms, e.g. forms changed through time.

Extinction-locations where fossils from older strata were lost, e.g. species went extinct

Father of paleontology whose studies of fossils revealed:

Scientific advances that influenced Darwin:Paleontology: Cuvier

Discovery of Fossils

• Impressions of organisms mineralized in rocks

Proposed the following theory of catastrophism to explain his observations

•Catastrophism-major changes in strata are the result of catastrophic events, e.g. floods or droughts

•Species are lost due to local extinctions as a result of catastrophe

•New species appear in next strata as a result of colonization

Paleontology: Cuvier

Scientific advances that influenced Darwin:Evolution: Wallace

Darwin’s contemporary

Came to same conclusion as Darwin

They presented their work together in 1858

Alfred Russel Wallace 1823-1913

Truth is born into this world only with pangs and tribulations, and every fresh truth is received unwillingly. To expect the world to receive a new truth, or even an old truth, without challenging it, is to look for one of those miracles which do not occur.

Alfred Russel Wallace