I am considering an article on the subject. From the historical evidence (which is limited because of the circumstances), modern 'gay culture' in the West appears to have emerged with the increasing urbanization of the early modern and industrial periods. The late 19th century sexologists were merely describing this secret culture. Alfred Douglas' poem 'Two Loves' certainly describes a very modern conception of homosexuality.

We didn't simply just emerge out of nowhere. The people who built that original culture would have had to existed before moving to the city, clearly found other like-minded homosexuals, and formed their subculture. So certainly 'homosexuals' would have had to exist prior to this point, otherwise there's no reason to form that subculture.

In terms of simply describing exclusively same sex attracted people, we have descriptions dating back well into antiquity. It is beyond me why it is a debate, and when you point this out, all you get back is 'oh that was too long ago.'. The invention of dildos predates the domestication of the dog, so clearly people weren't all that different than today.