I think that "introversion" and "extroversion" are largely inventions of modernity.
Most introverts are not anti-social, but find interacting with people with whom they do not have clearly-established relationships, and consequently do not have clearly-established mutual expectations with, to be stressful or emotionally draining, and their behaviour expresses the sort of aversion to or limited tolerance for stressful situations which is in itself nearly universal among human beings. In a simple band or village society, almost everyone you encounter on a daily basis is somebody with a clearly, often explicitly established relationship to you. Most interactions with people outside of that community are handled by specific individuals within the community, usually based on a demonstrated aptitude for dealing with strangers, or in more complex societies, established relationships with people outside of those groups. "Introverts" and "extroverts" do not exist in this society, because the sorts of situations which give rise to the behaviours which produce "introversion", or by juxtaposition "extroversion", do not exist.
In modern society, people are constantly thrust into contact with people who they do not have a clearly-established relationship: not only strangers, but co-workers or neighbours who recognised but do not really know each other. How easily or comfortably a person is able to carry out these interactions thus becomes a much more prominent aspect of their character, to the point of being interpreted as a fundamental characteristic. There are plenty of people who can appear "introverted" in certain contexts, and very lively in others, because "introversion" is not genuinely a description of that person at an essential level, but of how they respond to certain environments. The trick we've played on ourselves is framing certain environments as normal, as representing a plausible baseline of human experience and thus a basis on which to draw broad judgements about the essential characteristics of individual human beings, when in fact these environments are, in the long view, profoundly abnormal, and could only exist in a society structured in a specific, complex, and historically novel if not simply aberrant way. We put people in confusing and often hostile environments, and frame their responses to those environments as personality traits at best, and as actual pathologies at worst.
tl;dr: "introversion" is bourgeois ideology.