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15-2 Ideas That Shaped Darwin’s Thinking

15-2 Ideas That Shaped Darwin’s Thinking. By the time Darwin set sail around the world, numerous discoveries had turned up important pieces of evidence such as a rich fossil record.

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15-2 Ideas That Shaped Darwin’s Thinking

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  1. 15-2 Ideas That Shaped Darwin’s Thinking

  2. By the time Darwin set sail around the world, numerous discoveries had turned up important pieces of evidence such as a rich fossil record. • Fossils were challenging the traditional view of life, where scientists now thought thought there was several periods of creation, not just one.

  3. An Ancient, Changing Earth • Hutton and Lyell helped scientists recognize that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present.

  4. Hutton and Geological Change • In 1795, geologist James Hutton published a detailed hypothesis about the geological forces that have shaped Earth. • Most of these processes operate over the course of millions of years, so Earth therefore had to be much more than a few thousand years old.

  5. Lyell’s “Principles of Geology” • Darwin had been given a copy of Lyell’s Principles of Geology. Lyell stressed that scientists must explain past events in terms of processes that they can actually observe. • Lyell helped Darwin appreciate the significance of geological phenomena he had observed, such as a volcano erupting.

  6. Lamarck’s Evolution Hypothesis • Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. • These traits could then be passed on to their offspring. • Over time, this process led to change in a species.

  7. Tendency toward perfection • Over many generations, birds kept trying to fly, and their wings increased in size and became more suited to flying.

  8. Use and Disuse • For example, by trying to use their front limbs for flying, birds could eventually transform their limbs into wings.

  9. Inheritance of acquired traits • Lamarck thought that acquired characteristics could be inherited.

  10. Evaluating Lamarck’s Hypothesis • Lamarck did not know that an organism’s behavior has no effect on its heritable characteristics, however he was one of the first to develop a hypothesis of evolution.

  11. Population Growth • In 1798, Malthus published a book in which he noted that babies were being born faster than people were dying. • Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient food and living space for everyone.

  12. Darwin realized that Malthus’s reasoning applied more strongly to plants and animals than it did to people.

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