+1. Indeed, the entire post seems to glibly sidestep the question of what rational humans would do.

The author implies that we only have a rational interest in what happens during our lifespan. But many of us, through childbearing or other means, try to leave something of value behind us.

Irrational? Perhaps. But there's no reason pure hedonism should be any less irrational.

It also sidesteps the issue of people who plan/want to live indefinitely through advances in biotech, cryonics, mind uploading, etc. At the risk of distorting 'rational', if one personally cares at all about the future of humanity rather than just oneself in the present and immediate future it's easy to see why a course of action that helps humanity survive rather than hinders is a better, 'rational' course given that person's beliefs. Insert "moral dilemma" of the same flavor as being asked a preference on dying now, with everyone else living on, or living 5 more years then everyone including you dies.

Evolution is perfectly "happy" to sacrifice the interests of the species for those of the individual organism or gene.

That said, we're not slaves to evolution and can make our own choices for our own reasons.

A gene is happy to sacrifice the genes of other individuals - it is not happy to sacrifice copies of itself, no matter where they are found. Hence we tend to protect mammals more than reptiles, apes more than other mammals, humans more than other apes, our own countrymen rather than those from other countries, and our family more than others from our country.

But when it comes to the vexed question of getting those genes to survive beyond our own mortal shell, the correct genetic strategy seems to be to protect our offspring, even at the expense of ourselves, so we commonly see parents sacrificing themselves for children, in many different species.

And that is of course the flow in Stross's argument about there not being any reason not to colonise. Sure, you can't be on multiple planets, but your offspring certainly can be, so if one of those planets goes up in smoke, your genes will continue on through your children on other planets...

Only if that individual or gene is robust enough to found a new species or transfer to a new species. I mean, evolution will end up attempting it anyway, because that's how it works, but the aggregate effect of all the individuals & genes competing only helps the species more.

The survival of your species after your death is not a vested interest (a "special interest in protecting or promoting that which is to one's own personal advantage"). It affects you nil, by definition: you will be dead by then.

What affects you is having children before you retire, because then you'll be fed and survive a lot more than otherwise. Evolution is a conclusion of that, not the other way around.