Rejection Sensitivity (RS) may be an Adaptive System itself or a subcomponent of a larger one. RS is certainly adaptive, its intensity can be a problem or an asset depending on settings and prior experiences. I stereotype rural Iowa life as a place where RS is more of an asset than it is in urban settings. I personally would do badly (last hired, first run out of town) in the former setting; my adaptive systems for monitoring others' vocal quality and facial shifts are comparatively weak. I also have a rushed, intrusive style that tends to alarm the more cautious, tentative among us. The urban setting has its own challenges for shy persons and for the prickly, sensitive ones. A little psychostimulant is supposed to make intrusive people a little more thoughtful; a little extra serotonin makes us better able to handle a larger number of transient relationships. Pete Kramer (Listening to Prozac) called it cosmetic psychopharmacology.
You are correct about my ambivalence. George Williams wrote about semi-isolated, social groups of 10-100 individuals as ideal for maintenance of genetic (and behavioral?) diversity. While I still think that "hunter-gatherer minds" are likely to build hunter-gatherer cultures, it also appears true that population density, our communication gadgets, and our transportation make our social groups far larger and far more transient. These changes could magnify selection pressures to be aggressive, contingency-motivated, and less altruistic.
I personally think the kids do better in smaller schools (max = 300) and most of us do better in smaller settings. Perhaps a lot of us are keeping small groups for ourselves by withdrawal, by limiting the number of our primary social ties, and perhaps interacting with highly selective, like- minded people on the Internet! I do know parents who are ensuring their kids remained tied to the family unit; others perhaps are relieved that their argumentive, determined youngster is out to the mall to annoy other people.
About Van Gogh ... pick your favorite diagnosis & poor Vince possibly had it. I'm inclined to consider him bipolar. If so, then Prozac might have put him into a permanent manic phase and heightened his output. Likewise for Beethoven whose personal intensity and that of his father appear consistent with bipoar disorder.
Incidentally, your comments about becoming more like your parents and grandparents have encouraged me to post a short paper, entitled "Here Comes GrandDad Again," that I crafted 2 years ago. Expect it in the next 10 days.