“Platonic Ideal”. Scala Naturae: Great Chain of Being.

“Platonic Ideal”

Scala Naturae: Great Chain of Being

Implications of the Great Chain of Being

• Since God is perfect, his creation must be perfect

• A gradation must exist from inanimate objects through higher forms, complete with no gaps

• No gaps in the chain: no extinction, no new forms

William Paley (1743-1805)

• Natural Theology: or, Evidences of the Existence and Attributes of the Deity, Collected from the Appearances of Nature. (1802)

• “the watch must have had a maker”

18th Century began “The Age of Enlightenment”

• Newton’s explanations of physical phenomena lead to an increasingly scientific view

• Faith in progress and the power of reason

• The progress in geology suggested the Earth has undergone many changes and is very old

Charles Lyell, Principles of Geology (1830)

Championed the idea ofUniformitarianism: the forces molding the planet today have operated continuously throughout its history.

The formation of Earth's crust took place through countless small changes occurring over vast periods of time, all according to known natural laws.

The Earth is very old

Lamarck’s Theory of Evolution

I. Life originates through spontaneous generation then progresses up the great chain by moving along a set path (the different organisms we see today just began on this path at different times).

II. The production of new organs is brought about by need or want (an internal driving force).

III. Acquired new organs, or changes in organization, are passed on to future generations --> adaptation.

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Evolution of the long-necked giraffe

Charles Darwin(1809-1882)• Brief Biography:

– Went to school in Edinburgh to study medicine like his father

– Switched to the study of clergy at Cambridge – After school, Darwin signed on as ship’s naturalist

on the HMS Beagle

3 Influences on Darwin:

- Charles Lyell, Principles of Geology (1830)

- Thomas Malthus, Essay on the Principle of Population (1798)

- Voyage on the Beagle

Thomas Malthus, Essay on the Principle of Population (1798)

The rate of human population growth is greater than the rate of increase of food supply --> will lead to famine

Alfred Russell Wallace (1823-1913)Avid Naturalist: traveled to Malaysia and South America, collecting specimens to sell inorder to finance his trips

In 1858, while suffering from a bout of Malaria, came up with the theory of naturalselection independently of Darwin

Sent a few pages of “On the tendency of varietiesto depart indefinitely from the original type”to Darwin -->

Wallace and Darwin jointly present their ideas tothe Linnaean Society in London

1859: Darwin publishes On the Origin of Species by Means of Natural Selection, or the Preservation of

Favored Races in the Struggle for Life

• Major Theses of The Origin

– All species, living and extinct, have descended without interruption from one or a few original forms of life

– The process of natural selection is the primary cause for descent with modification