Darwin's Notion of Heredity
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"Darwin was an incredible genius," Livio told LiveScience. "His idea of evolution by natural selection is just mind-boggling — how he came up with something so all-encompassing as that. Plus Darwin really didn't know any mathematics so his theory is entirely non mathematical."
This feat is even more incredible given the notion of heredity (how traits are passed from parents to offspring) that Darwin and scientists of the time subscribed to would have made natural selection impossible. At the time, people thought the characteristics of the mother and the father simply get blended in the offspring just as a can of black paint and a can of white paint blend to create gray when combined.
Darwin's error was in not recognizing the conflict between this idea and his new theory. "If you introduce one black cat into a million white cats, the theory of blending heredity would just dilute the black color away completely. There's no way you would ever end up with black cats," Livio said. "Darwin didn't understand this, he really didn't catch this point."
It wasn't until the concept of Mendelian inheritance was widely accepted and understood in the early 1900s that the puzzle pieces of natural selection fell into place. Gregor Mendel proposed correctly that when traits from two parents come together, rather than blending, one or the other is expressed.
"As it turned out, Mendelian genetics worked precisely to solve this problem. In Mendelian genetics you mix more like you're mixing two decks of cards, where each card retains its identity — not like paint," Livio said.