There are several well-known characters in classical mythology who experience a change of sex, such as Tiresias (see Brisson 1976; Ugolini 1995) and Hermaphroditus (Ovid, Metamorphoses 4.285–388, with Robinson 1999). But there are also reports of girls and women who spontaneously acquire anatomical markers of maleness, not in myth but in real life, at specific times and places (Doroszewska 2013a: 224–5). It is these accounts of ‘real-life’ change of sex, particularly as related by authors active between the first century BC and the second century ad, that will be my focus in this essay. Their stories differ not only from mythical accounts of sexual transformation, but also from accounts of intersex children found in Roman historians’ reports of prodigies (e.g. Livy 27.11.4–5, 27.37.5–7, 31.12.6–10; Julius Obsequens 46, 81, 92, 94, 96, 107, 108, 110; see Krauss 1930: 130–3). Whereas the birth of intersex children inspired fear in a Roman population that viewed them as signs of severe divine displeasure (MacBain 1982: 127–35; Allély 2003), the reports of sexual transformation I consider are different. Intersex people – born with genitals that appear to combine masculine and feminine characteristics – display ‘simultaneous dual sexuality‘; people born with one set of genitalia that change to the opposite exhibit ‘successive dual sexuality’ (Brisson 2002: 2). Unlike the intersex infants drowned at sea during the Roman Republic, the people I will discuss were born as and assigned female at birth but transitioned across the gender boundary, lived to tell the tale, and even lived openly as men after transformation.

Reports of spontaneous sexual transformation are relatively rare in ancient literature. The most detailed narratives appear in the fragments of book 32 of Diodorus Siculus (32.10–12), written in the first century BC and preserved in the Bibliotheca of Photius, written in the ninth century ad (on Photius as a reader of Diodorus, see Botteri 1992: 28B9; Wirth 2008: 9B10; Rathmann 2016: 152). There are also shorter reports in Pliny the Elder's Natural History (7.36), a massive first-century ad work on aspects of the natural world, and the Περὶ θαυμασίων (On Marvels) by Phlegon of Tralles, a freedman of Hadrian active in the mid-second century AD.