Naroin stopped, shook her head. “Take it from an experienced hand, child. It’s no good blamin’ yourself for what you couldn’t prevent. Not so long as… - David Brin

A neurosis defends itself by coming up with rationalizations to explain away bizarre behavior.

"Worldwide Long Range Solutions Special Interest Group [ ¤ SIG AeR.WLRS 253787890.546]. Space Colonization Subgroup. Open discussion board.

Okay, so imagine we get past the next few rough decades and finally do what we should have back in TwenCen. Say we mine asteroids for platinum, discover the secrets of true nanotechnology, and set Von Neumann "sheep" grazing on the moon to produce boundless wealth. To listen to some of the rest of you, all our problems would then be over. The next step, star travel, and colonization of the galaxy, would be trivial.

But hold on! Even assuming we solve how to maintain long-lasting ecologies in space and get so wealthy the costs of star-flight aren't crippling, you've still got the problem of time.

I mean, most hypothetical designs show likely starships creeping along at no more than ten percent of the speed of light, a whole lot slower than those sci-fi cruisers we see zipping on three-vee. At such speeds it may take five, ten generations to reach a good colony site. Meanwhile, passengers will have to maintain villages and farms and cranky, claustrophobic grandkids, all inside their hollowed-out, spinning worldlets.

What kind of social engineering will that take? Do you know how to design a closed society that'd last so long without flying apart? Oh, I think it can be done. But don't pretend it'll be simple!

Nor will be solving the dilemma of gene pool isolation. In the arks and zoos right now, a lot of rescued species are dying off even though the microecologies are right, simply because too few individuals were included in the original mix. For a healthy gene pool you need diversity, variety, heterozygosity.

One thing's clear, no starship will make it carrying only one racial group. What'll be needed, frankly, are mongrels… people who've bred back and forth with just about everybody and seem to enjoy it."

You can’t fight biology. Only push at the rules, here and there.