Section 15-2

Ideas That Shaped Darwin’s Thinking

Before Darwin People Believed…

• Earth was created only a few thousand years before

• The planet and organisms haven’t changed

• Rocks and geological features were produced suddenly by events that

humans did not witness

James Hutton• Proposed that layers of

rock form very slowly

• Some rocks are uplifted, erosion wears mountains down

• These processes take a long time so the Earth must be older than a few thousand years

Charles Lyell

• Darwin read Lyell’s book during his voyage on the Beagle

• Proposed that process that shaped the Earth today are the same that shaped it in the past

• Encouraged explaining the past in terms of processes that can be observed today.

Hutton and Lyell Helped Darwin By…

If the Earth could change over time, couldn’t life change over time too?

The Earth must be extremely old. This helped support Darwin’s theory of life

changing.

Jean-Baptiste Lamarck

• Noticed that blacksmiths were usually muscular

• Noticed that their children would usually become muscular

• Hypothesized that being muscular was passed down from parent to offspring

• Used no scientific evidence

Lamarck’s Hypothesis

• Tendency Toward Perfection

-Change to live more successfully

• Use and Disuse

• Inheritance of Acquired Traits

-Can Pass on to Offspring

Thomas Malthus

• Darwin also read his paper on human populations

• “If human populations continued to grow, sooner or later there wouldn’t be enough space and food”

• Darwin wondered… What caused the death of so many plants and animals? What decides who dies and who survives?