Re: A galaxy of humans
If I remember history correctly, Birth-rates skyrocket when there's a need for it or the community in question doesn't have other diversions. Where a new colony was concerned, couples try to, well, pump out, as many children as they can. This was due to a combination of needing extra (non-paid) hands to work the fields as well as a high mortality rate in children and adults. It's been speculated that this is one of the larger factors as to why slavery took root big time in the Americas when it was going out of fashion in Europe.
For Colonies on other planets, one can reasonably expect that the colonists will have plenty of labor-saving devices, (tractors, if nothing else), as well as modern medicine, so birth-rates wouldn't be as great. They'd still increase with all that extra room on a new planet, but not as fast.