The search for the causes of transsexuality, of increasing interest in recent years, has focused on the intra-uterine life and on the physiological, neurological and molecular mismatches that the fetus could undergo. Through the analysis of different scientific materials that develop this explanation, this chapter presents the main rhetorical strategies that converge in biologising transsexuality and identity, with particular attention to their effects of power and to how and why their contents appear as unquestionable.

This discursive construction of gender and identity as natural and therefore universal, ahistorical and material entities, functions as a normative imposition of linear evolutionary development that places transsexualism, configured as an organic imbalance, within the field of expertise of medicine and its interventions. Based on a discursive analysis of explanations such as these, this chapter also reviews the colonisation of psychosocial explanations by biological hypothesis, the political and productive character of the pharmacological industry in gender terms, sexist roots of genital reconstruction surgeries, the double-performative effect of biologising identities and also the productive movement of medicine between depsychologising and psychopathologising transsexuality.