Can anyone share what the population levels are for huts? I built the one at the start, then one at 15 (but I think I could have been building at 14), and then 25. I am now at a population level of 67 with all my females pregnant, and still no hut in sight (do these things get start building multi-level basements as the game progresses)?

I'm needing a master parent, and am trying to reach a population plateau so my breeder can become experienced without becoming pregnant.