Re: After 200 generations in microgravity


[moderator's note: For readers of rec.arts.sf.science, please
note that this thread is crossposted into sci.bio.evolution. This is
a moderated group, primarily to keep out evolution vs creation threads.
This crossposting is okay with me, but if it wanders off-topic I'll
sever the crossposting without notice. - JAH]


On 22 mai, 19:14, Cryptoengineer <petert...@xxxxxxxxx> wrote:
On May 22, 11:59 am, DJensen <i_m...@xxxxxxxx> wrote:



Does this sound like the reasonable result of a combination of
physiological adaptations (both naturally selected and genetically
engineered) for an isolated human population living in microgravity on
asteroids that have been domed and terraformed, over 200+ generations?

In the region of 5000 years.

- Shortened spine
- Wider but shallower/flattened chest cavity
- Legs more arm-like but shorter; feet more like hands
- Longer neck
- Larger eyes, set farther apart
- Some webbing between fingers, armpits
- Longer arms and fingers (all four limbs)
- Smaller pelvis
- Average adult height (top of head to outstretched foothand) around
4'5"/1.4m
- Average adult breadth (fingertip to fingertip) around 7'/2.13m
- Delicate bones and less musculature
- Loss of (most) carnivorous characteristics; either fully herbivorous
or mostly herbivorous

Anything glaringly incongruent with what little we know of long term
microgravity exposure, or biology? Anything that would make you
immediately think "we'll that wouldn't happen"?

'Naturally selected'? What's the selection pressure? I don't really
see any environmentally driven selection occurring in a high-tech
culture, microgravity or not.

We do not yet have experience of millennia of high-tech culture,
whether environmentally-driven selection occurs or not.

Unless you can come up with
something that's going to kill off or sterilize people before
they're 20, no naturally selected genetic changes will occur.
There *may* be selection for people with changed metabolism,
to keep bones strong, or better radiation resistance. We now
build tools and change environments rather than let the
environment change us.

I suspect that artificially engineered changes will vastly
outpace any natural ones, and those will be driven by
style and mate-selection ('ooooh - he has cute tentacles')
as much as practical considerations.

A real example of a major genetic change in the region of 5000 years
is the evolution of lactose tolerance. Men have owned kine for less
than 10 000 years, and for much of the time men either kept them for
beef alone and did not milk them, or did milk them but fermented the
lactose and drunk sour milk or ate cheese. The ability of adult men to
stomach fresh milk has evolved.

What is the background natural level of adult lactose tolerance for
people who have never had kine, like Indians or Australians? There
must be some level of background mutations, or people could not have
evolved lactose tolerance!

Over just a few millennia, the very few people who could drink milk
fresh throve and bred while those who had to do without milk or
ferment it starved, withered and died. So people who still do not
stomach milk are still around but in definite minority.

Now, pelvis... cannot tell what the direction of evolution would be.

There is a strong housekeeping evolutionary pressure against small
pelvises. Women with small pelvises die in childbirth (and have no
offspring) or give birth to premature low birthweight babes (likely to
die in infancy).

Routine availability of caesarean section would remove that pressure.
As women with defective reproductive systems keep surviving and
reproducing, previously rare but persistent hereditary defects would
build up in the population. Which may include narrow hips.

On the other hand, in microgravity, the feet and hips lose the
function they are evolved for. In microgravity, many defects of feet
which would make the subject lame, movement restricted and a poor
marriage prospect have no effect.

What are the effects of unusually wide hips and pelvis? Do they hamper
walking?

Chinese altered the shape of many of their women´s feet, although this
seriously hampered them from moving and working. How easy would it be,
in microgravity, to evolve feet which have too long and opposed toes
to walk well in 1g?


.

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