[awb]

Much of what you say is reasonable.

Only two minor nits:

> why are humans the only creatures on Earth that have evolved those properties? Possibly language and a large brain are an evolutionary backwater.

Nearly every animal has language, for cooperation, competition, raising their young or to find a mate. Bees, whales, primates, birds, etc. all communicate strategically with some type of language.

> Given the history of humanity, I find it hard to believe that the population of a generation ship could survive as long as 100 years without war breaking out on-board. We've had large brains and language for about 50,000 years, as far as I can tell; we've been warring the whole time.

There’s been war somewhere the whole time, but not everywhere. Costa Rica, Iceland, Panama and several minor countries have no military: https://en.m.wikipedia.org/wiki/List_of_countries_without_ar...

It’s possible to find many countries who have not fought wars in the past 100 years. If you look more narrowly it’s possible to find communities unaffected by local war in hundreds or maybe even thousands of years (in other words, they fought a war but did so by traveling great distances, not fighting each other).

A ship would be much more like a tiny, isolated island colony rather than the geopolitical tensions that dominate the news.

Finally, wars rarely result in the extinction of both sides. Even if there was a large scale conflict it would likely be resolved prior to social collapse. There would be little incentive to kill so many of your fellow crew to the point where you’re putting every survivor at risk.

[mannykannot]

>> why are humans the only creatures on Earth that have evolved those properties? Possibly language and a large brain are an evolutionary backwater.

> Nearly every animal has language, for cooperation, competition, raising their young or to find a mate. Bees, whales, primates, birds, etc. all communicate strategically with some type of language.

There is currently only one species on Earth capable of even imagining the things being discussed here. On the other hand, it seems there may well have been more, but the others are now extinct.

One of these issues only we are discussing is the evolutionary viability of those abilities, and the fact we can do so suggests that it is, to some extent, up to us whether or not they will be.

[denton-scratch]

It's just struck me that a civilisation propagating through space can be envisaged a bit like light-cones, as in GR, except that the velocity factor isn't c, it's b (the maximum speed at which beings can move), which kinda depends on the beings.

But I think the cones thing is still interesting; it means that for any given maximum travel speed, there must be other civilisations that can never know anything about you, nor you about them.

[denton-scratch]

> Nearly every animal has language

Yes, I elided that bit, in the aim of brevity. I think there is a difference between human language and animal languages, in that human language is "creative" - we can freely create new utterances with new meanings, and expect to be understood. We know this of human language, but I would be very interested to learn of evidence of it in other species (chimps come close).