It seems odd to me that sexuality is a social construct even though gender is not. We know that gender is not merely a social construct because we know that gender dysphoria is not merely a social construct. (http://en.wikipedia.org/wiki/Gender_identity_disorder#Biolog...)

There isn't a logical conflict there of course, sexuality could be a social construct despite gender not being that simple, ...it just seems odd to me. I suspect that sexuality, like gender, is not that simple.

I don't think that's what phaer meant.

The concept of sexual orientation is a social construct. Unquestionably. It's an idea that's pretty much unique to our culture (modern western countries primarily). Other cultures throughout history had different concepts that were quite different.

The fact that different people experience sexual or romantic attraction differently, and that not everyone is simply attracted only to the opposite sex, is not a social construct. It's a fact.

So it can be both. Just like gender is both.

You have to distinguish between sex and gender. Gender is socially constructed, but it is a necessary social reaction to biological differences between the sexes (for example, everywhere maternity is generally biologically constructed, but everywhere paternity is socially constructed --- it is a matter of record who one's mother is biologically, but this is usually not a matter of direct record for paternity). The thing is there is a really complex relationship between biology and culture and gender itself highlights a lot of that complexity.

Add to that the fact that identity carries with it social constructs offered by society, cognitive and psychological individual factors, etc, and that this does not rule out some biological factors regarding how the individual relates to the rest of these.

So "merely" meaning to the exclusion of other factors, sure. But that doesn't mean that the social constructs might not even be at the forefront.