I'm rather skeptical of the whole "one mutation, one death" thing. That maybe could seem plausible, if mutation is viewed as a black box that randomly makes changes to the macroscopic properties of an organism, but from a biochemical view it seems rather bizarre.
First, each protein is coded for by a set of 3 base pairs in DNA, a codon. Since there are 4 bases, there are 64 possible codons. There are 20 (common) amino acids, so there are, on average, 3.25 possible codons per amino acid. Since the codons for a particular acid frequently differ in only one base pair, sometimes a single mutation will not change a protein at all. There will literally be no changes whatsoever. And in fact, biochemists have discovered that humans bearing the same genes, coding for the same proteins, frequently have different DNA sequences. A mutation of this sort seems unlikely to cause even one death.
Secondly, it is entirely possible to change the primary sequence of a protein (the sequence of amino acids) without changing the three dimensional structure at all, or in minimal ways. When biochemists are studying a new protein, a frequent test is to change single amino acid residues, and observe the impact on protein function. Most of the time, it really doesn't do much. There are always a few amino acid residues which, when changed, completely prevent the protein from functioning, but there are usually only a handful of that type of residues in an entire protein (which contain hundreds of amino acids). And then, if a mutation did something like swap out an asparagnine for a glutamine would do very little, since their chemical properties are very similar. (as a side note, I do not endorse, nor did i even read, the pages where those links go. I just did an image search). Many mutations like this won't really do anything.
Mutations become even less harmful if the target is some sort of folded RNA. You would have to have dozens of mutations within a single short strand of DNA before you could even notice a change in the secondary structure of a folded RNA molecule.
Could someone point me to something on evolutionary biology that discusses the one mutation, one death principle in more detail? I'd like to know if I'm missing something here.
"One mutation, one death" is, of course, silly if taken literally - but the idea might have some utility if the purpose is to establish an upper bound on the quantity of information that selective deaths can provide.
Today's post, Natural Selection's Speed Limit and Complexity Bound was originally published on 04 November 2007. A summary (taken from the LW wiki):
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