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"Nothing in biology makes sense except in the light of evolution."

-- Theodosius Dobzhansky, Geneticist

A Poll: Which is the most highly evolved species?

evolution - change over time.

organic evolution - genetic (and phenotypic) change of living organisms over time. Sometimes a very looooong time.

The Age of Things

Using radiometric dating techniques, scientists have been able to estimate the time that our universe, solar system, earth, and life itself first showed up.

If you think of earth's entire history as having happened in 24 hours, modern humans have been here for about 3 seconds before midnight.

Origins and Evolution

The Origin of Life is NOT the same as Evolution of Life.

Science addressing these two things are interrelated and complementary, but origin does not equal evolution. A history:

  • As long ago as 500 B.C, Greek philosophers were already toying with the idea that life was constantly changing. However, the most influential of these, Plato and his student, Aristotle, believed in an unchanging world in which all species had been created in a perfect state, with perfect interactions intact.

    Aristotle believed that life forms could be arranged on a scale of increasing complexity, a scala naturae, that was fixed and unchanging.

    In a Divine Creator's world, evolution would be counterproductive, since the world should already be perfect.

  • The Old Testament account of The Creation fortified this idea. As recently as the 1700's, biology was done in a framework of natural theology: the idea that science should be dedicated to studying nature in order to figure out the Grand Plan of the Creator.

    But where did life come from?

    The Origin of Life: The Life and Death of a Popular Idea

    Ancient Romans started it, and the idea persisted through mediaeval times: living organisms could spring fully formed from non-living material. This process was termed spontaneous generation and was inspired by every day observations...

    It took the work of more than one scientist to finally lay the idea of spontaneous generation to rest. It took the work of more than one scientist to finally lay the idea of spontaneous generation to rest.

  • Francesco Redi

  • Anton van Leewenhoek

  • Georges Buffon

  • John Needham

  • Lazaro Spallanzani

  • Louis Pasteur

    Miller-Urey: The Modern Understanding

    In the 1950s, Stanley Miller and Harold Urey duplicated the conditions of the primordial earth in this now-famous apparatus:

    The experiment yielded many of the organic building blocks of life, including amino acids, sugars, and even nucleotide bases.

    The most important feature of the apparatus was the LACK OF OXYGEN. Oxygen was very scarce in earth's earliest atmosphere, or these complex organic molecules would have been fried as soon as they formed.

    Organic Evolution: Change in Living Things Over Time

    The idea that living things came from non-living matter had been put to rest. But some wondered how it could be that there was such a diversity of life on earth.

  • Jean Baptiste Lamarck

  • Georges Cuvier

    Among these scientist creationists was a young student named Charles Darwin.

    Darwin may well be the most influential scientist of all time. His controversial work, On the Origin of Species by Means of Natural Selection, (published in 1859) is arguably the most important biological work ever written, and every aspect of modern biology is framed in the context of evolution by natural selection.

    (Recent understanding of epigenetic inheritance suggests that while Lamarck may not have quite hit the mark, not all inheritance is strictly Mendelian. And as we'll see later, not all evolution is strictly Darwinian.)