"Jonathan Silverlight" wrote
in message ...
In message , Peter Webb
writes

"F. Kuik" wrote in message
...
Eric The whole time humans are on Mars they will be in their space
ship,or in their space suits. Their bodies will never touch Mars.
They
will be kept warm(68F) Shielded from harmful radiation,and won't stay
long.

If technology gets better they can stay longer and longer. It's also
true
that the human body does change alot in space. Bone structure for
example.
So what happends is really to find out yet.


Yeah, but those changes are not inheritable. For there to be changes in
future generations, there must be some form of natural selection.
Further,
they must be adaptations which are of benefit prior to child bearing age.

Its taken 50,000 years for different races on earth to evolve, and we are
still quite obviously a single species. I suspect future life on Mars
would
differ from future life on earth by less than (say) the life of an Eskimo
10,000 years ago differs from the life of an Australian Aborigine 10,000
years ago, so the pressure causing evolotionary divergence would be less.

Except that we are all living in a 1G gravity field and a given solar
radiation - though only the Australian and his or her African
counterpart takes that unprotected. The Inuit can't even survive in his
chosen environment without artificial aids.
Living on Mars might cause our descendants to grow at the rate of 1 inch
per century. If they decide they like that, they might be 12 feet tall
well before your 10,000 years, and interbreeding will become difficult
:-) Add to that biochemical changes, as they decide to adapt to a lower
oxygen level - perhaps the minimum possible to our current physiology,
or beyond.
--

No. If I grow 1" taller due to low gravity, this doesn't mean that my
children *inheret any genes* for being taller. They may grow 1" taller, and
their children 1" taller, and 10,000 years downstream they will still only
be 1" taller than somebody from earth, and if their children returned to
earth after 10,000 years of ancestors living on Mars, they would be no
taller at all.

The only way that changes in a population can affect successive generations
is if they increase the "fitness" - the chances of living to reproductive
age and bearing children. Eskimos are short and fat not because they have
eaten seal meat for 10,000 years, but because the tall skinny ones died of
hypothermia before reproducing. Native africans are black not because they
have had good suntans for thousands of years, but because the white ones
died of melanoma before reproducing (actually, its a little more complicated
than that, but you get the idea). Giraffes do not have long necks because
their ancestors were always stretching their necks, they have long necks
because the ones with short necks died of starvation before reproducing.

So for Martians to have a genetic change which tends to make them taller,
you have to identify a mechanism which confers an evolutionary advantage on
taller Martians - some reason why they are more likely to survive to child
bearing age and reproduce. (Similar to why Giraffe's have long necks). I
could not (and cannot) think of any such mechanism, which is why I said it
would be unlikely. The only example I can think of where there may be an
evolutionary advantage from a genetic change is one I gave in my original
post - tolerance to radiation. I don't think adaptation to lower oxygen will
cause evolutionary pressure, unless there are people dying from asphyxia -
which doesn't sound like my idea of a well run colony.