Some mutations can result in a survival advantage, but how that
leads to natural selection to the advantage of the species is more
complex. Take the SARS virus. It was probably a mutation that
converted a virus that caused a zoonosis to jump species and infect
humans. So it had a wider number of suitable hosts and I suppose
one might think that is an advantage. But it was pretty virulent
too and killed many of its hosts. Does that confer a survival
advantage?
No, it does not. If the host dies, it dies with the host. However,
as viruses do, they mutate again and again (since they have such
rapid replication rates). In the end, it appears that a less
virulent strain survives and co-exists in harmony with its host
(subsequent SARS cases in China became progressively less serious
and now we don't even hear of it) whilst the original virulent ones
died with its victims.
I believe in natural selection and the possibility of evolution.
Whether humans have evolved from apes is another story. For
evolution to result in the emergence of man, it will require a very
long period to evolve. I understand the arguments between
creationists and evolutionists lie with the age of the earth. That
is crucial. If the earth is too young, there would not be enough
time for evolution to lead to the emergence of humans from
primitive unicellular organisms. Given that we can extract DNA and
even proteins from fossils (osteocalcin has been extracted from
dinosaur fossils), creationists argue that the earth is not as old
as it is made out to be. I don't know if that's true, but it does
strike me as amazing that you can extract proteins from dinosaur
bones millions of years old when my western blot fails if my nurse
forgot to freeze a sample quickly enough.
Another (rather old) piece of information I remember reading in the
journal Science some 10 years ago struck me as being rather odd.
They found a very high proportion of amino acids in the levo
isoform within some ancient fossil. Amino acids in organic tissues
are in the L-form. Given that amino acids racemize within a
definite period of time, it is surprising that the scientists did
not find a racemic mixture after all these milliions of years. The
creationists would argue that it proves the earth is only thousands
of years and not millions of years old. But without the millions of
years, humans cannot be here today, even if the theory of evolution
is true.
As organisms become more complex (with longer lifespans and lower
reproduction rates), you need to wait far longer for mutations to
result in significant natural selection. The move towards sexual
reproduction means that a mutation must occur in the gonads to be
passed on to its progeny. A mutation in your skin cell can give
rise to cancer, but it cannot be transmitted to your children.
Given the short reproductive life of complex organisms like humans
(from about 13 to 45 years old), the fact that the woman can only
release one egg each month and lactation for one baby eliminates
the chance of further pregnancy, future evolution of humans will
take even longer.
Given the diminishing reproductive rates of humans, perhaps it will
be some other species that will evolve quicker and in the event of
a global catastrophe such as another meteorite attack, it might
well be another animal that will adapt fast enough to rule the
earth.....Cats maybe, Starblue?
