I'd like numbers/evidence on it too, but for my own generation, I compared my cousins for years precisely about overprotectiveness, and those who were only protected against extreme imminent danger have succeeded in life way further (for their starting conditions, socially and economically) than those who had my aunts all over them not letting them fall and have scrapes.

Anecdotally, again, the parents of those who did NOT fall on dirt were much more wealthy, so these cousins of course inherited (so to speak, their parents aren't dead) the wealth and status, but gosh, they do everything they are told to do, what to study, etc. While those who did fall frequently when babies these days have generated about half of the wealth the others inherited and they are vocal, really nice professionals and of course awesome people to spend time with.

Girls were more protected than boys, regardless of everything else.