There's a strong survivorship bias here - the uncontacted tribes tend to be in places that are isolated, and are unsuitable for agriculture or mining. I'm not sure we can infer much about the pre-agricultural lives of people in more normal environments from observing these groups.

Wouldn't we at least be able to derive some data about child mortality and spread of disease and such? Admittedly some of this would be guesswork if they are truly uncontacted and only surveilled and surveyed remotely.