History of Evolutionary Thought

What was the view of the world and nature before Darwin? Static Universe The universe didn’t change through time Problem - Fossil Evidence

What was the view of the world and nature before Darwin? Static Universe 2. Earth Centred Universe Galileo - showed that this was wrong

What was the view of the world and nature before Darwin? Static Universe Earth Centred Universe Great Chain of Being Problem - how do you incorporate new species?

What was the view of the world and nature before Darwin? Static Universe Earth Centred Universe Great Chain of Being Argument from Design Each species was designed for a specific purpose Problem:

How did this ‘traditional’ view (or Natural Theology) apply to Biology? Argument from Design The design of all organisms showed that there was an intelligent and benevolent Creator BUT…. How do disease organisms fit into this scheme ? Ebola

How did this ‘traditional’ view (or Natural Theology) apply to Biology? Argument from Design The design of all organisms showed that there was an intelligent and benevolent Creator OR…. Why did some species go extinct?

How did this ‘traditional’ view (or Natural Theology) apply to Biology? Argument from Design Relationship between Species (Great Chain of Being) BUT .. vulnerable to extinction

How did this ‘traditional’ view (or Natural Theology) apply to Biology? Argument from Design Relationship between Species Fixed Species and Relationships How do you incorporate new species?

General Summary: The world/universe was designed by a benevolent Creator to function perfectly and its form and function were fixed through all time.

But Evolution is about change What were the pre-Darwinian ideas of change through time?

Pre-Darwinian Ideas of Organic Change 1. Georges Louis Leclerc, Comte de Buffon (1707-1788) Species - a distinct group maintained by reproduction Local Conditions Different species Ancestor Time

Pre-Darwinian Ideas of Organic Change Georges Louis Leclerc, Comte de Buffon (1707-1788) Jean-Baptiste Lamarck (1744-1829)

Pre-Darwinian Ideas of Organic Change Georges Louis Leclerc, Comte de Buffon (1707-1788) Jean-Baptiste Lamarck (1744-1829) Lamarck’s ideas: 1. Spontaneous generation

Pre-Darwinian Ideas of Organic Change Georges Louis Leclerc, Comte de Buffon (1707-1788) Jean-Baptiste Lamarck (1744-1829) Lamarck’s ideas: Spontaneous generation Ascent up the scale of nature Different species Complexity of the organism Time

Pre-Darwinian Ideas of Organic Change Georges Louis Leclerc, Comte de Buffon (1707-1788) Jean-Baptiste Lamarck (1744-1829) Lamarck’s ideas: Spontaneous generation Ascent up the scale of nature Acquired characteristics

Originators of Modern Theories of Natural Selection Alfred Russell Wallace Charles Darwin

Voyage of HMS Beagle

Darwin’s Finches - Geospiza Galapagos tortoise - Geochelone

Contributing Elements to Darwin’s theory 1. Charles Lyell (1797 - 1875) Gradualism (Uniformitarianism) All change through time can be explained by processes at work today No need to invoke catastrophic events

Contributing Elements to Darwin’s theory Charles Lyell (1797 - 1875) Thomas Malthus (1766 - 1834) Populations of organism will grow faster than their food supply Population Number Food supply Time

Contributing Elements to Darwin’s theory Charles Lyell (1797 - 1875) Thomas Malthus (1766 - 1834) Plant and Animal Breeders showed that the form of a species could be changed over time

This differential reproduction/survival is natural selection Logic of Darwin’s Theory of Natural Selection (or Descent with Modification) Observation Deduction All organic populations can exponentially. In spite of Obs. 1, they don’t. There is some kind of struggle for existence. All members of a species are not the same. Differences in individuals are passed to their offspring. 2. Some members of a species are better equipped to survive and reproduce than others. This differential reproduction/survival is natural selection