grammar - A question introduced by "wonder"

Granted that it is an idiomatic phrase, I still wonder how people came to say it*.*

Granted that it is an idiomatic phrase, I still wonder how people came to say it*?*

Granted..., I still wonder how did people came to say it*?*

I am interesting in wonder governing clause, but not exactly know how to use it. Which version is right? Which is the best?