If you keep your game on 1/2 speed, you can finish all the puzzles (except the cemetary which requires a death) with all your original villagers. There is good news/bad news about 1/2 speed. Good news, they don't age as quickly but you can get tech points just as quickly. Bad news is.. they don't age as quickly so takes longer to nurse and the kids to grow up. But, I've completed all puzzles with only 14 adults... it can be done... takes LONGER.. but doable. There's a lot more to the 1/2 speed issue as far as food goes, the food bin does not go down as quickly so you don't "have" to farm as much. Which, is good news since it takes a lot longer for the crops to come up and subsequent renewing.