>>>For most of history, most people lived in horrible squalid conditions. Whole families (sometimes several families) would live in a room or two <<<
Where? What planet? What country? What year?
In this country, at least, that type of life would have been the norm until at least the 1920's.
The idea of the nuclear family (mom, dad and 2.1 children) living in their own house or apartment is the norm didn't really come about until after WWII.
NYC, mid 1800's tenanements.(sp)