There is a reference to socialisation with purusha-napunsaka being differentiated from napunsaka, meaning, the masculine queer being differentiated from the default feminine queer. There is also a reference to active (padisevati) and passive (padisevavati) homosexual acts in Buddhist literature. All these ideas emerged between 5th century BCE and 5th century CE, and were explored in the following centuries.
The purpose here was, however, very different from modern gender studies, which seeks to create an ideal world where all manners of choices are permitted, respected and celebrated, and there is no imposition of patriarchal hetero-normative structures. Ancient Indian gender studies, by contrast, were designed to appreciate the diversity of nature, as well as to identify those who could become monks, outgrow sexual desire and liberate themselves from all karma.