What it does mean though is

这么说的意思是
that it doesn't seem to follow as a biological adaptation.

这种现象完全不符合生物适应的规律
The puzzle is not why is it

问题不是为什么
that some men have sex with men.

男人会和男人做爱
That's not a big puzzle.

这不是个大谜团
Maybe they have sex with men as some sort of recreational things

可能他们和男性做爱就是为了好玩
or pair bonding or whatever.

或表示亲密或其他的什么原因
That's not the puzzle.

但这都不是问题
The puzzle is why are there some men

问题是为什么这些男人
who don't want to have sex with women?

不和女人做爱呢
Similarly, why are there some women

同样的为什么有些女人
who don't want to have sex with men?

不想和男人做爱呢