My Question: ORIGIN OF LIFE. Why do textbooks claim that the 1953 Miller-Urey experiment shows how life's building blocks may have formed on the early Earth--when conditions on the early Earth were probably nothing like those used in the experiment, and the origin of life remains a mystery?
NCSE's Answer: Because evolutionary theory works with any mo^del of the origin of life on Earth, how life originated is not a question about evolution. Textbooks discuss the 1953 studies because they were the first successful attempt to show how organic molecules might have been produced on the early Earth. When modern scientists changed the experimental conditions to reflect better knowledge of the Earth's early atmosphere, they were able to produce most of the same building blocks. Origin-of-life remains a vigorous area of research.
My Response in Outline:
(a) Most biology textbooks include the origin of life--and the Miller-Urey experiment--in their treatments of evolution. If the NCSE feels that the origin of life is really 'not a question about evolution,' the organization should launch a campaign to correct biology textbooks.
(b) Because the Miller-Urey experiment used a simulated atmosphere that geochemists now agree was incorrect, it was not the first successful attempt to show how organic molecules might have been produced on the early Earth. When conditions are changed to reflect better knowledge of the Earth's early atmosphere, the experiment doesn't work.
(c) If the origin of life remains a 'vigorous area of research,' it is only because origin-of-life researchers are dedicated to their work, not because they have discovered anything that demonstrates how life originated.
My Response in Detail:
(a) The NCSE's claim that the origin of life is 'not a question about evolution' ignores the fact that most biology textbooks include it--along with the Miller-Urey experiment--in their treatments of evolution. For example, Campbell, Reece and Mitchell's Biology (5th Edition, 1999), one of the most widely used introductory textbooks for college undergraduates, discusses the Miller-Urey experiment in Unit Five: The Evolutionary History of Biological Diversity. Similarly, Mader's Biology (6th Edition, 1998), Starr and Taggart's Biology: The Unity and Diversity of Life (8th Edition, 1998), Schraer and Stoltze's Biology: The Study of Life (7th Edition, 1999), Guttman's Biology (1999), Audesirk, Audesirk and Byers's Life On Earth (2nd Edition, 2000), and Purves, Sadava, Orians and Heller's Life: The Science of Biology (6th Edition, 2001) all feature the Miller-Urey experiment in their sections dealing with evolution. Alberts, Bray, Lewis, Raff, Roberts and Watson's upper-division textbook for biology majors, Molecular Biology of the Cell (3rd Edition, 1994), discusses it in a chapter titled 'Evolution of the Cell.' The Miller-Urey experiment is also standard fare in upper division and graduate-level textbooks devoted entirely to evolution, such as Futuyma's Evolutionary Biology (3rd Edition, 1998) and Freeman and Herron's Evolutionary Analysis (2nd Edition, 2001). If the NCSE feels that the origin of life is really 'not a question about evolution,' the organization should launch a campaign to correct biology textbooks.1
(b) The 1953 Miller-Urey experiment used a simulated hydrogen-rich atmosphere of methane, ammonia, hydrogen and water vapor. By 1970, however, geochemists were nearly unanimous in agreeing that the Earth's primitive atmosphere was nothing like this. Excess hydrogen is quickly lost to space because the Earth's gravity is too weak to hold it, so the early atmosphere would almost certainly have consisted of gasses emitted from volcanoes--mainly carbon dioxide, nitrogen and water vapor. When this more realistic mixture is put into a Miller-Urey-type apparatus, the experiment doesn't work. Stanley Miller himself reported in 1983 that the most he could produce in the absence of methane was glycine, the simplest amino acid, and then only if free hydrogen were present. But free hydrogen is precisely what geochemists now agree was essentially ABSENT. So the Miller-Urey experiment was unsuccessful, and NCSE's claim that it was the first successful attempt to show how organic molecules might have been produced on the early Earth is false. The NCSE's claim that 'when modern scientists changed the experimental conditions to reflect better knowledge of the Earth's early atmosphere, they were able to produce most of the same building blocks is also false. 2
(c) If the origin of life 'remains a vigorous area of research,' it is only because origin-of-life researchers are dedicated to their work, not because they have discovered anything that demonstrates how life originated. As New York Times science reporter Nicholas Wade wrote in 2000: 'Everything about the origin of life on Earth is a mystery, and it seems the more that is known, the more acute the puzzles get.' 3
http://www.evolutionnews.org/2008/08/inherit_the_spin_the_ncse_answ.html#more
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