Much has been made of native people who have high levels of type II diabetes while eating a Western diet but who become healthier when they eat something approximating a 'traditional' diet. I think that would provide a clear example of diversity that was once advantageous but has become deleterious in recent times. Haven't also claims been made about genetic morphs related to Alzheimer's that they protect the brain from the consequences of starvation early in development? And of course there's good old Sickle Cell Anemia, which exists as a side effect of selection pressures for a trait which is quite advantageous... if there are endemic problems with malaria in your area, which thankfully is no longer the case for most of us.

"I used to see a distinction between “sociopaths” (#1) and “psychopaths” (#3). It seemed helpful, so why has it disappeared?" People thought they understood what the terms meant, so the APA had them abolished. Keep in mind that poor impulse control isn't necessarily a feature of sociopathy - it's just the one that tends to make people visible as obvious sociopaths. Actors and politicians often score very highly on manipulative behavior, but they're often also the ones that can behave according to societal expectations - when it benefits them.