If there are no more places to buil...
If there are no more places to build then get your population up and new foundations for small huts will appear.
If you need more elders quickly then get a female villager that is over 50 years old to Master Scientist and Master Farmer. Then find a male villager and keep putting those two together (dont wait for them to go indoors) and get them to kiss lots of times. They should becaome a Master Parent after a little while.