Re: Is the mechanism for evolution entirely understood?

The mutation within genetic information takes place during meosis, the
production of sex cells (spems and eggs). In (at least) human females the
eggs are produced before they are born. In human males, sperm is produced
"on demand", throughout life. If any "random" mutation is going to occur,
it's at this point. Female eggs suffer from degredation in quality as they
age. This is why there are high risks of problems with older women having
babies.

The mutation that occurs in meiosis is principally random, but can be
affected by such things as radiation, and maybe diet, etc. It still remains
random, even if due to an external force, there is no process which goes
along the lines of "it's getting hotter around here, better adjust the
sperm to allow for that." That would imply that our bodies understood our
genetic makeup, which woulod be some feat. The mutation is very small and
very unlikely. 

It's not always necessary for mutation to occur in order for evolution to
occur and an apparent adaption to be seen. The gene pool for a species may
contain a huge variety of different genes, the "combination" of which are
important. Recessive genes play an important part in making sure that the
gene pool of a species stays nice and varied.

Let us take the example of my dog, a border collie. Border collies are
principally long haired, but mine is short. That is not due to some recent
mutation in the border collie gene pool, it's merely because the gene for
short hair is recessive and people prefer long haired ones, so breeding is
forced to make it much more likely to be long haired.

Let us imagine that global warming goes mad and the temperature in England
goes up to Barbados proportions. If the border collies were left to roam
free and breed without human intervention, I'm pretty sure that we would
find that the long haired collies would find it a lot harder, and maybe
die. All of a sudden, the short haired ones would be everywhere. This would
be called an adaption, but would not have been the fault of a mutation,
just a different mix of genes.

Mutation gives us extra variety, but the variety already present can often
be enough to give us adaption.