The nature of asexuality has made it a fairly unknown orientation throughout history. I mean, look at the things it has going against it!
1) According to most sources, only about 1% of the population is asexual.
2) It's defined by the lack of sexuality, not an openly "different" sexuality.
3) In many, if not most, historical cultures, love has been a secondary matter in marriage and sex. As such, asexuals would not have found anything unusual about not being attracted to their partners.
4) It's likely that asexuals would have taken the "just suck it up" approach to sex.
5) Like homosexuality, it would have historically been considered a problem, psychological, medical, or other (demons have stolen your sex drive, or whatever tripe medieval and puritan people would have used).
I'd say all of these are major factors today as well (with the possible exception of #3). So it's no wonder that asexuality hasn't become apparent until the last few years. Even though asexuality is gaining visibility online, it is still lacking in real-world visibility.
I think this is the biggest issue with asexuality right now. It can't continue to exist as an "Internet orientation". Even if asexuals don't particularly want to "come out" to friends and family, there should be some more effort to show up at meetups and the like. Community-building is crucial, because the more visible you make the community, the less chance you give the rest of the world to dismiss asexuality because of its nature or its beginnings.
Unfortunately, I live in a rural area for college and don't have the same large population to pull from for meetups. Thankfully I have two close asexual friends at home in Texas. However, I'll soon be starting my own personal campaign of asexual community-building in my college. Even if only 1% of the population is asexual, I have numbers on my side: in a college of 1500, with most living on-campus, about 15 should be asexual. That's more than almost any meetup I've heard of, and that's just on a small college campus. There's hope left for community building, even in rural areas. And maybe I'll take my chances and drive to Philadelphia for the Pennsylvania meetup--but a 3 1/2 hour drive might be a bit much!
Maintaining the asexuality bibliography
3 years ago