Can sexuality change over time?

Yes. When I was about 18 I wanted to fuck all the time. Now that I am approaching middle age, I am happy to do it some of the time. Plus, my girlfriend does not like the word fuck when it applies to loving sex. So now I enjoy making love. :)
Change is good.

Not really. You can mask it from yourself for a while, but it will emerge.

We veer towards that which we need. If we perceive females are more nurturing then we would seek female lovers and when we need protection, male lovers. However both those characteristics can be found in both sexes I know. It still stands as a good theory though. All round, sexuality is liquid.

I don’t think it really changes, but that our perception of it may. In the past, at least, young people were notoriously insecure, and it often didn’t occur to them to be anything but straight or to use any other position than missionary. As we get older, we get more comfortable with ourselves, and may become more flexible in our attractions.

If you’re talking about sexual orientation, then I have this theory that sexual orientation isn’t black and white. It seems to be pretty black and white among most people—hetero or homo—but maybe that is just because people are secure with their orientations.
I wonder if anybody has had a dramatic sexual orientation change.

I believe that sexual orientation is fluid for some people. It may just be that a person has never been interested in a certain gender until that one person comes along and so for a time they are interested in that person’s gender, but then are no longer interested in that gender again. As some people discover themselves they find themselves discovering their sexual orientation is different than they thought. Some people repress their sexuality for a while until it comes up again. But honestly I think sexuality is something that’s different to every person and shouldn’t really be labelled like it is because of that.

At the risk of being politically incorrect, I have to agree with @laineybug. Look at how heterosexual people adapt to homosexual experience when imprisoned and cut of from their previous love objects. Many retain a bisexual, opportunistic approach to finding mates even after release.

I think more people are naturally bisexual but think they’re not. When I was in my teens I yo-yo’ed between thinking I was straight or gay, because it seemed that I changed just about every year. At 18 I decided I was bi, and have been happy with that label ever since. I tend to slide up and down the kinsey scale over time. So yes, I think some people can appear to change their sexuality but in those cases I think it’s just an emergence of latent bisexuality.

Why couldn’t it?
It’s all made up shit.
We didn’t even have a concept of “sexuality” as a realm of behavior and identity until the mid-late 19th century.
Humans are far more complicated than normative science allows for.

@bookish1 I will second that!

@tups: Thanks. It’s something I’ve been thinking about since the onset of adolescence… And to answer the rest of your question, I have been all kinds of queer, and for myself personally, I tend to view sexuality as a description of tendencies, rather than a prescription of limits. I have been bi and gay both as a female and a male. I was never in denial about “my true sexuality”; I was growing and expanding my interests and experience. Now, I tend to say I’m “mostly gay” because I am much more interested emotionally and physically in men than in women, but I am open to that changing.

Just recently a (fairly new) friend of mine was telling me that in his younger years he considered himself gay, not even bi, he was only interested in men. However, since an encounter with a woman that he felt a strong attraction to about 15 years ago, he has not been attracted to men and now considers himself straight. He said he was shocked, at the time, by the sudden change.