On Thu, 31 Jul 2003 22:36:34 -0400, "Tony Sivori"
<TonySivori@yahoo.com> wrote:

Bryan Derksen wrote:

On Wed, 30 Jul 2003 00:22:24 -0400, "Tony Sivori"
<TonySivori@yahoo.com> wrote:

Mike Williams wrote:

They don't need to transport significant numbers at any one time between
the stars.

Why not? Do you think the Mayflower brought two Europeans to America, and
then no more? It didn't happen that way.

The Americas were already inhabited when Mayflower made its trip. The
native Americans were all descended from a few small bands that made
the trip over the Berings land bridge.

Which proves my point. It takes a lot more than a single breeding couple.

No, that only proves that it can be done by a few small bands. It says
nothing about whether it can be done by a single breeding couple,
since we don't know if it was tried or not.

"A few small bands" is a reasonable population for a very small
self-sufficient space habitat, aka generation ship, in any event.

All you need to populate a planet is a few dozen individuals. If

Which reminds me of a fantasy of mine, but I suppose that is off topic here.
=-)

you've got sperm banks, you don't even have to worry too much about
tailoring their diversity. If you've got artificial wombs, you don't
need to send _anyone_ to start a colony.

And who would raise these children, teach them how to survive, to get along,
to maintain a recognizable form of your culture, and the ways of high
technology? Robot nannies? If you have machines that good, just send them
instead.

I believe the original scenario used the assumption that a colony
world wouldn't start sending out new colony ships of its own for a
thousand years. You don't _need_ to maintain a recognizable form of
your culture and the ways of high technology - they can reinvent them
themselves, if need be. Or leave a digital library in orbit that's
responsive to basic radio transmitted queries to help them along, if
you want to speed things up a little.

My only point here is that genetic diversity is not going to be any
kind of a problem, even if you're limited to sending a very small crew
on your colony ship. The other details are irrelevant.

Oh, and self-replicating robots would present the exact same problem,
Fermi-wise, if you do have machines that good. Personally, I suspect
that that's what we'll ultimately send out to colonze the galaxy in
real life - not humans, but the machines descended from them.

Inbreeding only causes problems when the starting population has
deleterious recessive genes in it. If you carefully select your
starting population to be free of defects, then the children will be
fine.

I suspect there are no such individuals.

So _make_ some. If you've got the technology to build and launch a
starship, you've probably got some pretty good genetic technology as
well.

And if there were, due to normal
background radiation (never mind the high levels they would absorb on the
trip) they would not stay that way. One stray x-ray and your super clean
gene superman (or superwoman) is just another flawed slob like the rest of
us.

Background mutation rates result in only a handful of heritable
mutations every generations, and the vast majority of those are
silent. Sure, you could have some bad luck and get a few "bad genes"
in your starting population - but that's not necessarily going to kill
the colony. The cheetah population on Earth is descended from just a
handful of individuals after it suffered near-extinction 10,000 years
ago <http://www.cheetah.org/?html=aboutcheetah-03>. While the species
does suffer from its inbreeding, it's not a death sentance - and
they'd be doing really well if there were no competitors, as would be
the case with a newly-arrived colony ship in an empty solar system.

Besides, you can't rely on occasional bad luck to solve the Fermi
paradox, because colony ships keep getting sent out. Most would not
have such genetic problems, and a few failed colonies are irrelevant
to a species' overall expansion.

Interstellar is a snap, on these timescales.

Then why aren't they here?

That's exactly the point of the Fermi paradox.