Natural sex reversal in vertebrates

Abstract

The phenomenon of sex reversal and hermaphroditism in vertebrates has been observed since early human history dating back to Aristotle, who also recorded that the , a sea-bass, reproduced without copulation. Despite their common occurrence and early discoveries, hermaphroditic animals, with or without sex reversal, aroused fear rather than interest before the eighteenth century; the laying ‘cock’ and the crowing ‘hen’ were usually put to death in accordance with the medieval laws (Evans 1906). The first experimental approach to intersexuality and sex reversal in vertebrates commenced with the work on birds and domestic mammals by John Hunter, who once gave an account to the Royal Society of London in 1780 on a most extraordinary pheasant, which ‘ after having produced several broods, moulted, and the succeeding feathers were those of a cock. This animal was never afterwards impregnated . . .’ (Marshall 1964).