I don't think it is correct to say that the child came up with hypothesis testing independently.

From Wen Gong's profile, she's a software engineer. So clearly, the child has one parent who regularly would language such as: "well, if X was the case, then Y should have happened. But Y didn't. So X is very unlikely" (aka debugging) and so on. I'm also sure that the child had access to good books, education, TV, the Internet, other smart kids and adults.

So there may be hope for humanity, if all of humanity had access to all of the above.