The point is that Glenn doesn't want to tell anyone what his point was.
Your point seems to be pointless. The mutation could have occurred at
any time, and similar mutations in terms of function likely occurred
many times in all lineages that have existed for a reasonable length of
time. The mutation was caused by a transposable element. If you look
into the literature you will see that transposable element mutagenesis
has a highly variable rate of occurrance even within a lineage.
Specific genes under certain genetic backgrounds can have mutation rates
of up to 10-5 or higher for specific genes (about 1 in 100,000). These
types of mutations are usually more common than single nucleotide
mutations. 10% of your genome consists of just one type of transposable
element (ALU) and it is just one of many that you have in your genome.
These transposable elements are parasitic and jump around your genome to
make more copies of themselves. Retrovirus are a type of transposable
element that can cause viral diseases when they become active. So these
types of mutations are happening all the time.
In the current human population everyone has on the order of 100 new
mutations that they have inherited from their parents. There are over 7
billion people alive so that would be around 700 billion new mutations
in our current population. The human genome is only 3 billion total
base-pairs, so nearly every site in the human genome has been hit by a
new mutation multiple times in just the current generation. There is
nothing magical or mystical about mutation. A lot of these new
mutations are lost to the next generation because a lot of humans do not
reproduce. Half of your new mutations are lost if you only have one
child. If that child does not reproduce all are lost.
If the mutation is neutral (doesn't do anything bad enough to be
selected against) it will be lost or increase in frequency just by
chance. If a mutation has a selective disadvantage it will be selected
against and has little chance of increasing in frequency in the
population. The current hypothesis is that melanistic moths were
selected against in the environment that existed before we polluted the
planet, and would have been at a selective disadvantage. The fact that
this was a recent mutation that had not been segregating in the
population for a long period of time, likely means that it was selected
against because we expect such mutations to occur routinely. Where do
you think that melanistic mice, dogs, cats, chickens etc came from? If
you wait long enough these mutations obviously occur. This is no big deal.
Really, similar mutations in terms of function likely have occurred many
times in the history of this species. The one that they have identified
just happened to appear and be selected for. The previous ones were
lost. Even a mutation with a high selective advantage can be lost due
to chance. A lot of moths get eaten or die from parasites or disease.
In a few generations a similar mutation is likely to occur.
So what is your point, or do you realize that you didn't have one?
Ron Okimoto