The Barbarian
Crabby Old White Guy
- Apr 3, 2003
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The first 3 related more to abiogenesis. Current biology maintains that abiogenesis and evolution are separate. i.e. falsifying any particular hypothesis or theory for abiogenesis won't falsify evolution (so it's another important precept to get out there). However, starting with a few propositions on genesis events helps set the stage. So, here we go:
1. Suppose multiple independent genesis events produce life. How probable is it all of these events would converge on the same (or similar) physics-based mechanisms: 20-some amino acids, RNA/DNA-like self-replication, and a cellular structure? (+2 to -2)
Quite likely convergent evolution would occur. And it has. On the other hand, if there were multiple independent origins of life, it's astonishingly unlikely that DNA would turn out to be as though the different taxa evolved from a common ancestor. Which is what we see. So this evidence is strongly against multiple origins of life for any of the life forms currently known. As you suggest, the difference between analogous organs like bird, pterosaur, and bat wings, would not show common descent, but the biochemical and genetic data from those organisms certainly would show common descent.
A similar case involves fish, whales and penguins, all of which have similar shapes and appearance in water. But (for example) the horizontal flukes of whales compared to the vertical fins of fish are explained by the ancestry of whales from land animals. Again, the distinction between analogy and homology makes the hypothesis of multiple origins so unlikely as to be out of the question.
2. Suppose multiple independent genesis events occur at different times. How probable is it conditions would have been suitable for these events during the Cambrian,
Ordovician, Silurian, Devonian, and Carboniferous radiations? (+2 to -2)
Depends on whether or not you invoke magic to do it. A natural origin of life from the earth(edit: in a world with existing life) as described in the Bible would be highly unlikely because any high-energy compounds would quickly be used up by existing bacteria, before they could form living systems. If one imagined new life was poofed into existence, than any conditions would be sufficient.
3. How probable is it different genesis events would produce different expressions (phenotypes)? (-2 to +2)
About as likely as common descent would do that. But of course, different genesis events would not produce the common genetic data known to form a family tree for all known living things. And we know this is valid, because we can test the idea by comparing DNA from creatures of known descent.
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