[webmaven]

> Our ancestors from 50M years ago are all extinct. So a civilisation spreading through the galaxy would have evolved in all kinds of different ways. It's not obvious to me that these diverse evolutionary strands would all still be interested in Dyson spheres, or space travel, or even astronomy.

There is no need for all, or even most, of the civilizational variants to retain those characteristics. As long as some variants do, civilization would continue its inexorable interstellar spread, it would just end up being lumpy rather than a relatively even wavefront.

Indeed, survivorship bias would seemingly tend to conserve the required characteristics and possibly start constraining the ways in which civilizational offshoots can vary. And it isn't hard to imagine stay-at-home variants succumbing to the influence of later arriving spreader variants to become spreaders once more.