I have a wacky, potentially controversial yet thought provoking inkling as to the cause of these inferiority feelings. But first some background. I've often felt inferior at various times throughout my life, I was bullied every day for 8 years on the school bus. I'm Scandinavian Japanese American, which, despite my skin being a ghastly shade of pale egg shell, still makes me a minority, something inherently globally different. With this in mind, we can get on to my wacky idea.

In your opening paragraph you asked where do these feelings come from but, you also point out that these feelings or the mechanism responsible for causing them is useful. Perhaps it flew over my head but you never elaborated on how these feelings are useful.

These feelings have never really been all that useful to me. Sure, some peer pressure is healthy for reinforcing societal norms but the feelings you described which I do relate very much to, are of little benefit to our individual selves. Rewind a cosmic second (500 years) and they suddenly seem very useful. If you step back and watch the whole planet continue to rewind feelings of insecurity mushroom periodically all over the globe, typically on the ruins of a collapsed empire or infrastructure. Yet it's not the fallen emperors who feel insecure, it's the majority of the human populations. Now, this is where my idea might rub people the wrong way, but I suppose that because serfdom (including slavery) was treated as an inheritable trait, traits that are useful for surviving life as a serf long enough to produce offspring would unfortunately also be selected for in the evolutionary history of those people.

So what sorts of traits are useful to a serf or slave? Feeling inexplicably inadequate, aversion to making eye contact and protests, and having a preference for staying home. Serfs and slaves with these awkward traits would live longer then their peers who "stood up" for themselves against their lord's bullying, which included beatings for leaving the property with out permission (a punishment that could be very deadly in an era without accessible antibiotics and antiseptics). Resigning oneself to a life of grueling inferiority was sadly a key to long and successful life in those days.

It'd be nice to feel like a viking samurai, but the numbers are simply stacked against it, even for a Scandinavian Japanese American, all of my ancestors were exposed to some form of feudalism during their respective histories. Indeed the only thing that makes me feel powerful, truly, consistently and irrevocably, is designing 3D models and printing them. A pastime not unlike silversmithing or running a printing press which were vital to the success of the revolution. It's my profoundly colonial American flavor of technophilia & innovation that inoculates me against the tyranny of socially imposed genetic injustice.

It's probably different for you since you're originally from the UK.

lol & cheers