People

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Before Darwin, two ideas about life on Earth prevailed

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1. Species are fixed, or permanent. They do not change.
2. The Earth is less than 10,000 years old.
These ideas were challenged as people became aware of the incredible diversity of organisms, past and present, and the nature of Earth’s geological processes.

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Buffon

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In the mid1700s, the study of fossils led French naturalist to suggest that Earth might be much older than a few thousand years. He observed that specific fossils and certain living animals were similar but not exactly alike.

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Lamarck

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In the early 1800s, another French naturalist, Jean Baptiste Lamarck posed that life evolves, or changes. He recognized that species are not permanent. Lamarck explained evolution as a process of adaptation. An adaptation is considered to be an inherited characteristic that improves an organism’s ability to survive and reproduce in a particular environment. Today Lamarck is unfairly remembered in large part for his mistaken explanation of how adaptations evolve. He proposed that by using or not using certain body parts, an organism develops certain characteristics. He thought this characteristics could be past on to offspring. He called this idea inheritance of acquired characteristics. Problem: do acquired characteristics change DNA and are they heritable?

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Darwin – Video.

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1. Descent with modifications: Descendants of early organisms spread into various habitats over millions of years. They accumulated different modifications, or adaptations to diverse ways of life.
2. Natural selection is the mechanism for evolution. Those individuals with inherited characteristics suited to environment will leave more offspring.

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Lyell

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Geologist Charles Lyell had a particularly strong influence on Darwin. He proposed that gradual and observable geologic processes such as erosion could explain the physical features of today’s Earth. An example is the gradual erosion of a river bed cutting a canyon. This required more time than a few thousand years. Ideas point to two conclusions.
1. Earth must be very old
2. Slow and gradual processes occurring over vast spaces of time could cause enormous change on Earth.

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Malthus

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Essay on human populations – contended that much of human suffering: disease, famine and homelessness was due to human population’s potential to grow. He suggested that populations grow faster than the rate at which supplies of food and other resources can be produced. This leads to a struggle for existence.

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Wallace

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Came to the same conclusions as Darwin with the same mechanism for evolutionary change as Darwin. Both of their writings were presented in public. Then Darwin published The Origin of Species and is given the credit for these ideas.