1. Ideas that shaped Darwin’s thinking
Section 16.2

2. Geological breakthroughs
During Darwin’s time, humanity's understanding of the Earth was changing rapidly
James Hutton and Charles Lyell famously suggested that the Earth of extremely old, and that processes that occurred in the past are the same processes that operate in the present
Uniformitarianism
Hutton presented his work in 1785
Lyell published his first great work – principles of geology in 1830

3. James Hutton – Age of the Earth
Hutton made a number of observations of the Earth
He linked together a number of geological process
Cooling magma to make igneous rocks
Uplift to make mountains
Erosion to reduce mountains and make sedimentary rocks
All of these processes take a very long time
Introduce the concept of deep time, and that the Earth must be more than a few thousand years old

4. Charles Lyell – Uniformitarianism
Lyell argues that laws of nature are constant, and that scientists must be able to explain past events in terms of processes that occur in the present
Concept of uniformitarianism - the present is the key to the past
Volcanoes released lava and gas in the past the same way they do today
Rivers erode canyons the same way they do today
The Earth needs to be old enough to be able to form the numerous structures and phenomena that we can see across it’s surface
Darwin read Lyell’s book, and it influenced his understanding of the world
Darwin asked if the Earth can change over long periods of time, can animals?

5. Did anyone come up with the idea of evolution before Darwin?
Yes!
Throughout the 19th Century, the fossil record gave the idea that life had somehow evolved
A Frenchman – John Baptiste Lamarck proposed that organisms could change during their lifetimes, by selectively using or not using parts of their bodies
Acquired traits could be passed on to offspring, enabling species to change over time
Published in the year Darwin was born

6. What does this mean?
Lamarck suggested that all organisms have an inbuilt drive to become more complex and perfect
Organisms will change and acquire features that make them live more successfully in their environment
Example – water bird could develop long legs as it began to wade in deeper water looking for bird
The body could adapt to it’s new surroundings
Traits altered by an organism were called acquired characteristics
He proposed that if a bird acquired a new trait, such as longer legs it could pass it on to it’s offspring

7. Why were Lamarck's ideas incorrect?
Organisms don’t automatically want to become perfect
Evolution does not mean that organisms want o become better, nor does it happen in a predetermined direction
Traits acquired by individuals can not be passed on to offspring
But, he did recognize that species are not fixed
He tried to explain evolution using natural processes
He recognized a link between environment and body structures
His work paved the way for people like Darwin

8. Thomas Malthus
In 1798, Thomas Malthus recognized that humans were being born faster than they were dying
This resulted in overcrowding
He proposed that if population growth continued unchecked there would not be enough space for everyone
War, famine and disease were three factors that control population growth
Darwin took Malthus’s work and applied it to nature
In nature, most offspring die before they reach maturity, and only a few manage to reproduce
Darwin used this theory to investigate why certain individuals in a population survive, and look to see if there was any pattern

9. Artificial selection
Darwin investigated changes produced by plant and animal breeders
Breeders know that individual organisms vary, and it is possible to pass on these traits to offspring
Used to improve crops and livestock
The process of farmers breeding specific animals or plants for certain characteristics is called artificial selection
Nature provides the variation, and humans use what is useful
Darwin tested the idea of artificial selection by breeding fancy pigeons

10. Why is this important?
At first Darwin didn’t recognize the importance of variations within a species
Thought to be minor defects
Darwin recognized that these minor defects provided the possibility for evolution
This is the basis for his theory of evolution

11. Assignment
Discuss with you neighbor the key people who influenced Darwin and his theory of evolution
Create a timeline in your notes displaying this key bits of information
Use the textbook to help you
Add as much detail as possible
Current understanding in the world at each time period
What each scientist did
How their contributions helped to change the general understanding of the world
Basic example to help you on page 459 – but go into more detail!