"Faith" writes:
And if the mutation that brought about the tail is simply the recurrence of a formerly expressed allele, in my book that's not a mutation
Sorry, but you don't get to supply your own definition for the word mutation. It already has a well accepted definition, and what you're doing amounts to moving the goal posts. Let's take another look at what Equinox wrote.
"Equinox" writes:
AATACGTGTTGTGAC, and it promotes tail growth, then a mutation, say to
AATACGTGTTGTGAT, may render it nonfunctional. That gene may then be selected for (since maybe women find a shorter tail sexy), and so later humans could all have the second version. Then, in a baby in Spain in the 20th century or some such, a mutation occurs that switches it back to a C, or to an equivalent nucleotide, since the system is redundant anyway:
AATACGTGTTGTGAC. So the baby has a tail due to the mutation, revealing our evolutionary past (since the rest of the genetic mechanism for making a tail is still there).
There are two similar, yet differently functioning strings of DNA.
AATACGTGTTGTGAC - tail-forming
AATACGTGTTGTGAT - non-tail-forming
If both parents had only the non-tail-forming string of DNA, and their child received the tail-forming string of DNA, that is a mutation, plain and simple.
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