Race ages are how much experience your race has gotten.
First Newborn, then Infantile, then Young, then all the way to Ancient *2000000 Points?*.
You gather experience from researching new tech, wars, winning wars, ship construction, colonization and just about everything else.
There was a bug where if you triggered something you would be Shot all the way up to Ancient; had some races that I got Ancient because of it. It's fixed now; but I would like to hear from people who actually noticed the
bonuses you get from old age