God doesn't make people, people made God.

God was invented by rich people to keep poor people from killing them.

Lets go get some ice cream.....

I'd probably say that some people think that god made people from dirt, but I think that's silly. We know that people evolved from other life forms over very long times and we aren't sure exactly how life originally arose but we aren't going to find out by making up stories.

I would feel particularly free to say this to the child of an atheist. Kindly and gently, of course.

I’d ask him what he thinks. You may be off the hook right there. If he presses, I might explain that nobody really knows, but here are some examples of what different people believe, and remind him that nobody is sure. Then I’d ask him again what he thinks about it.
I think it’s important at this age to avoid influencing his own understanding; that’s what organized religions do.
Good luck, however you proceed!