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Descent With Modification (Evolution):

NATURAL HISTORY BEFORE DARWIN:

Essentialism -

Foremost in Plato's philosophy - concept of 2 co-existing worlds. A perfect world we conceive with our intellect and an illusionary (imperfect) world that we perceive with our senses. For Plato: variation in plants and animals was merely imperfect representations of their essential or ideal forms.

The Scala Naturae -

Teleology: belief in a divine order or purpose to life

Aristotle ordered species according to a Scala Naturae or Great Chain of Being

Species are fixed forms, on a scale from simple to complex.

All species characteristics are purposeful.

Natural Theology and Taxonomy -

Carolus Linnaeus sought to bring order to the diversity of life in his text Systema Naturae dedicated to the 'greater glory of God'.

He founded modern taxonomy by developing a system of Latin binomial nomenclature.

Linnaean Classification - hierarchical but not evolutionary

Inclusive hierarchical ranking.

Unique Latin binomial nomenclature, Genus species.

This classification was based on morphological similarity and the assumption of fixity of a species, not evolutionary descent.

Similarity can be quite misleading about evolutionary relationships.

Taxonomy and Biodiversity -

300BC: Aristotle recognised 600 animals.

1600AD: about 1000 named animals.

1758AD: 10th ed of Systema Naturae classified 4400 animals, 7700 plants.

Today: 3m named species, 30-50m estimated.

SETTING THE STAGE FOR DARWIN:

Physical Sciences -

Copernicus and Galileo, later Newton and Descartes.

Replaced the will of God (Aristotelian teleology - purpose for which events occur) with a concept of efficient cause

- mechanisms that cause events to occur.

Fossil Record -

Cuvier: founder of modern vertebrate palaeontology.

Life's history is recorded in fossil-containing strata.

Each stratum is characterised by unique fossils.

The older the strata the more the fossil organisms differed from modern organisms.

Extinction is common in Earth's history.

But Cuvier didn't consider this as evidence for evolution. Instead:

-Believed in the Doctrine of Special Creation and the fixity of species.

-Believed boundaries in strata and extinction events corresponded with catastrophes with the most recent being the Biblical flood.

Catastrophism: theory that major changes in Earth's crust are the result of catastrophic events rather than gradual processes of change.

Geology and the Age of the Earth -

James Hutton: proposed that major landforms could be explained by mechanisms currently operating in the world.

Gradualism: theory that profound change is the cumulative result of slow continuous processes.

Charles Lyell: explained gradualism in book - Principles of Geology.

Darwin greatly influenced by Lyell and Hutton's conclusion:

-Earth must be ancient.

-Very slow and subtle processes persisting over a long time can result in dramatic change.

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