So atheism is admittedly not an innate human trait, but neither is theism--you may be born with predispositions towards beliefs (which, importantly, is absolutely no measure of the validity of those beliefs), but not beliefs themselves. How, though, is atheism "maladaptive?"
A dependant child cannot (safety-wise/survival-wise) afford to be a non-believer in AUTHORITY. Life depends on "going along" with the custodial parent figure.
This should fall away around the time of individuation. But, often it does not.
Dependency continues into adulthood and the intellect atrophies. Religion, as a viral infection, does the rest.