How to train new builders?!

Hi,

So I may have screwed myself over. I already built the first and second new huts and cleared the beach, and over time all the villagers who worked on those (and became adept builders) died of old age. I'm pretty sure you need a builder for either the idol challenge or the temple challenge, but I don't know how to get a new builder.

What do I do? Can I train villagers by having them examine huts, or something? Or do I have to start over?