quote:
Nobody studied it. The hypothesis itself is dismissed beforehand.
So the idea that arc-organisms contained enough DNA variation to result in the species we see today is untested. This means it is little more than a guess, wouldn't you say. And even worse, it is an untested hypothesis that is used to support the theory that two to seven of every species fit on the ark. This is what we call an ad hoc hypothesis. Making up untested, and sometimes untestable, hypotheses to support a larger theory or to refute contradictory evidence. This is looked down on in scientific circles. The only reason for the hypothesis of arc-organisms is to do away with contradictory evidence and nothing more. This hypothesis was not derived from observation, but rather to uphold a story in an ancient text.
But here is one example of why the arc-organism hypothesis is discounted beforehand:
Mol Biol Evol. 2004 Jan;21(1):36-44. Epub 2003 Aug 29. Related Articles, Links
Temporal patterns of fruit fly (Drosophila) evolution revealed by mutation clocks.
Tamura K, Subramanian S, Kumar S.
Center for Evolutionary Functional Genomics, Arizona Biodesign Institute, and School of Life Sciences, Arizona State University.
Drosophila melanogaster has been a canonical model organism to study genetics, development, behavior, physiology, evolution, and population genetics for nearly a century. Despite this emphasis and the completion of its nuclear genome sequence, the timing of major speciation events leading to the origin of this fruit fly remain elusive because of the paucity of extensive fossil records and biogeographic data. Use of molecular clocks as an alternative has been fraught with non-clock-like accumulation of nucleotide and amino-acid substitutions. Here we present a novel methodology in which genomic mutation distances are used to overcome these limitations and to make use of all available gene sequence data for constructing a fruit fly molecular time scale. Our analysis of 2977 pairwise sequence comparisons from 176 nuclear genes reveals a long-term fruit fly mutation clock ticking at a rate of 11.1 mutations per kilobase pair per Myr. Genomic mutation clock-based timings of the landmark speciation events leading to the evolution of D. melanogaster show that it shared most recent common ancestry 5.4 MYA with D. simulans, 12.6 MYA with D. erecta+D. orena, 12.8 MYA with D. yakuba+D. teisseri, 35.6 MYA with the takahashii subgroup, 41.3 MYA with the montium subgroup, 44.2 MYA with the ananassae subgroup, 54.9 MYA with the obscura group, 62.2 MYA with the willistoni group, and 62.9 MYA with the subgenus Drosophila. These and other estimates are compatible with those known from limited biogeographic and fossil records. The inferred temporal pattern of fruit fly evolution shows correspondence with the cooling patterns of paleoclimate changes and habitat fragmentation in the Cenozoic.
Genetic studies can corroborate, through mutation rates (not degeneration) that D. melanogaster shared a common ancestor with D. simulans 5.4 million years ago, and 62.9 million years ago with the rest of the fruit fly subgenus Drosophila. This agrees with the fossil record and biogeographic data. Unless you think that the flood occurred 60 million years ago and random mutation was involved, this isn't exactly consistent with the arc-organism hypothesis.
[This message has been edited by Loudmouth, 03-17-2004]
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