devoted to gender studies. Other sciences, such as sexology and neuroscience, are also interested in the subject. The social sciences sometimes approach gender as a social construct, and gender studies particularly do, while research in the natural sciences investigates whether biological differences in females and males influence the development of gender in humans; both inform the debate about how far biological differences influence the formation of gender identity and gendered behavior. In some English literature, there is also a trichotomy between biological sex, psychological gender, and social gender role. This framework first appeared in a feminist paper on transsexualism in 1978. Etymology and usage Derivation The modern English word gender comes from the Middle English gender, gendre, a loanword from Anglo-Norman and Middle French gendre. This, in turn, came from Latin genus. Both words mean "kind", "type", or "sort". They derive ultimately from a Proto-Indo-European (PIE) root *ǵénh₁- 'to beget', which is also the source of kin, kind, king, and many other English words, with cognates widely attested in many Indo-European languages. It appears in Modern French in the word genre (type, kind, also genre sexuel) and is related to the Greek root gen- (to produce), appearing in gene, genesis, and oxygen. The Oxford Etymological Dictionary of the English Language of 1882 defined gender as kind, breed, sex, derived from the Latin ablative case of genus, like genere natus, which refers to birth. The first edition of the Oxford English Dictionary (OED1, Volume 4, 1900) notes the original meaning of gender as "kind" had already become obsolete. History of the concept The concept of gender, in the modern sense, is a recent invention in human history. The ancient world had no basis of understanding gender as it has been understood in the humanities and social sciences for the past few decades. The term gender had been associated with grammar for most of history and only started to move towards it being a malleable cultural construct in the 1950s and 1960s. Before sexologist John Money and colleagues introduced the terminological distinction between biological sex and gender as a role in 1955, it was uncommon to use the word gender to refer to anything but grammatical categories. For example, in a bibliography of 12,000 references on marriage and family from 1900 to 1964, the term gender does not even emerge once. Analysis of more than 30 million academic article titles from 1945