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 model 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)
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My Question: DARWIN'S TREE OF LIFE. Why don't textbooks discuss the 'Cambrian explosion,' in which all major animal groups appear together in the fossil record fully formed instead of branching from a common ancestor--thus contradicting the evolutionary tree of life?
NCSE's Answer: Wells is wrong: fish, amphibians, reptiles, birds, and mammals all are post-Cambrian--aren't these 'major groups'? We would recognize very few of the Cambrian organisms as 'modern'; they are in fact at the roots of the tree of life, showing the earliest appearances of some key features of groups of animals--but not all features and not all groups. Researchers are linking these Cambrian groups using not only fossils but also data from developmental biology.
My Response in Outline:
(a) The NCSE is wrong: Fish DID make their first appearance in the Cambrian explosion.
(b) The 'major groups' to which my question refers are the animal phyla. Fish, amphibians, reptiles, birds and mammals are sub-groups (classes) of a single phylum. The NCSE is using semantics to give the illusion that the Cambrian explosion never happened.
(c) It is through assumption and extrapolation, not 'fossils' and 'data from developmental biology,' that Darwinists are supposedly 'linking' the Cambrian groups.
My Response in Detail:
(a) The fossil record shows that fish were among the animals that made their first appearance in the Cambrian explosion. (4)
(b) Fish, amphibians, reptiles, birds and mammals are not the 'major groups' to which my question refers. As every biologist knows, animals are classified into a hierarchy of groups: species, genera, families, orders, classes, and phyla. The phyla are the several dozen major categories that distinguish mollusks, arthropods, echinoderms, annelids and chordates, among others. (Modern representatives of the five phyla listed include snails, insects, starfish, earthworms and mammals, respectively.) Fish, amphibians, reptiles, birds and mammals are sub-groups (classes) of the chordate phylum. Since fish first appeared in the early Cambrian, this phylum was present in the Cambrian explosion, even though not all of its sub-groups were. Representatives of the five phyla listed here, and most of the other phyla as well--the 'major groups' of animals recognized by all biologists--appear in the Cambrian explosion, with no fossil evidence that they evolved from a common ancestor. Berkeley paleontologist James Valentine and his colleagues wrote in 1991 that the Cambrian explosion 'was even more abrupt and extensive than previously envisioned' and gives the impression that animal evolution 'has by and large proceeded from the 'top down'. 'This does not fit Darwin's theory that major differences should have evolved over millions of years from minor differences in a single ancestral species--that is, from the 'bottom up.' By labeling vertebrate classes 'major groups,' the NCSE uses a semantic trick to give the illusion that the Cambrian explosion never happened, and that the conflict with Darwin's theory doesn't exist. Similarly, most biology textbooks avoid any mention of the Cambrian explosion, and the few that do mention it try to dismiss it. The NCSE, like the textbooks, is concealing a problem with the fossil record so significant that Darwin himself considered it a 'valid argument' against his theory. (5)
(c) The NCSE's claim that 'researchers are linking these Cambrian groups using not only fossils but also data from developmental biology' is profoundly misleading. First, the principal lesson of the Cambrian explosion is that the fossils needed for 'linking' the phyla to a common ancestor are nonexistent. Second, with a few rare exceptions developmental data are available only from living animals. Although embryological similarities and differences can help us to classify living animals into phyla, we can only speculate how most extinct animals developed. Darwinian researchers ASSUME the existence of a common ancestor, and then extrapolate modern similarities and differences hundreds of millions of years into the past to guess what the hypothetical ancestor might have been or how it might have developed. Thus it is through assumption and extrapolation, not 'fossils' and 'data from developmental biology,' that Darwinists are 'linking' the Cambrian groups.
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