HISTORY OF EVOLUTIONARY THEORY

Observation leads to ideas…ideas are influenced by other ideas

Historical Context of Evolutionary Theory

Aristotle (384-322 B.C.) “scale of nature” all living forms could be arranged on a ladder. Each form assigned a rung, all rungs were taken. God was at the top followed by Man.

Plato (427-347 B.C.) Two worlds: real/ideal world that is eternal and world of imperfection we perceive through senses. Living things were created in their perfect, static form by the gods.

Natural Theology

A philosophy dedicated to discovering the Creator’s plan by studying nature- the earth and it’s inhabitants.

Adaptations were evidence that the Creator had designed each and every species for a particular purpose.

Classifying species was a major objective.

Carolus Linnaeus (1707-1778)

Specialized in taxonomy- naming and classifying the diverse forms of life.

Developed binomial nomenclature- a two part naming system.

Developed a system of grouping similar species into a hierarchy of increasingly general categories. (species- genus- family)

He saw no evolutionary relationships in his groupings.

Georges Cuvier (1769-1832)

Largely developed paleontology- the study of fossils. Opposed to the idea of evolution. Advocated catastrophism, the principle that events in

the past occurred suddenly and by different mechanisms than those occurring today.

Each boundary between strata corresponded to a catastrophe (drought, flood, super volcano) destroyed many of the local species.

Area repopulated by immigration.

Tree of Life

instead of a ladder or hierarchy…

tips of branches

Fathers of Modern GeologyHutton & Lyell

1795 James Hutton, Scottish geologistExplained Earth’s geologic features by the theory of Gradualism: Speciation occurs gradually, profound change is the cumulative product of slow but continuous processes.

Charles Lyell (1797-1875) geologist Incorporated gradualism into the

theory of Uniformitarianism: Geologic processes have not changed throughout Earth’s history. Forces that build and erode mountains occur at a steady rate, thus Earth is much older than previously believed.

Strata of sedimentary rock at the Grand Canyon

IMPORTANT CONCLUSIONS: Earth must be very old much older than six thousand years

(it is 4.5 billion years old) Very slow and subtle processes persisting over a long period

of time can add up to substantial change. Slow but significant changes in environments caused slow

but significant changes in species over “geologic time.” By the end of the 18th century several naturalists, including

Darwin’s grandfather Erasmus Darwin, suggested that life had changed as environments changed.

No one had suggested a mechanism.

The Inheritance of Acquired Characteristics

Jean Baptiste de Lamarck proposed the first explanation that was widely accepted for years.

Three parts:1) Use and disuse described how body parts of organisms can develop

with increased usage, while unused parts weaken. Correct.2) Inheritance of acquired characteristics described how body features

acquired during the lifetime of an organism (such as muscle bulk) could be passed on to offspring. Incorrect.

3) Natural transformation of species described how organisms produced offspring with changes, transforming each generation into a slightly different form that is more complex. Species did not become extinct nor did they split and change into two or more species. Incorrect.

The Giraffe

Short neck. Food scarce. Stretch neck. Eat. Have a slightly longer neck. Have offspring with slightly longer

neck. Repeat. Inheritance of Acquired

Characteristics or Lamarckism

Descent with Modification via Natural Selection by DARWIN

Charles Darwin 1809-1882 Med school dropout BA Natural Theology Captain Fitzroy- HMS Beagle

5 years of travel UNPAID Galapagos, islands of relatively

recent volcanic origin, 900 km west of SA coast.

Gathered much evidence Waited 20 years to write and

publish a groundbreaking book.

Alfred Russell Wallace(1823-1913)

Presented a paper with identical ideas as Darwin on July 1, 1858 at the Linnaean Society meeting

Was a botanist who came up with virtually the same concept of natural selection more or less independently through his studies on the Malay archipelago. Darwin panicked because he was not ready with his book yet!

On the Origin of SpeciesBy Means of Natural Selection November 24, 1859

Darwin’s groundbreaking book explained what had once seemed a bewildering array of unrelated facts.

He focused on:• Diversity of organisms• Similarities & differences• Geographic distribution• Adaptations to surrounding environments