The one-sex and two-sex theories are two models of human anatomy or fetal development discussed in Thomas Laqueur's book Making Sex: Body and Gender from the Greeks to Freud.
Laqueur theorizes that a fundamental change in attitudes toward human sexual anatomy occurred in Europe in the 18th and 19th centuries.
[7] Laqueur's theories have been subject to criticism by scholars including Katharine Park, Robert Nye, Helen King, Joan Cadden, and Michael Stolberg for misrepresenting and omitting evidence by earlier scholars, as well as for drawing an overly concrete portrayal of the shift from one-sex to two-sex models.
"[8] Until the beginning of the eighteenth century, Laqueur claims, the one-sex model dominated medical and philosophical literature and there was a web of knowledge to support it.
Laqueur uses examples from ancient thinkers to help support his claim to the dominance of the one-sex model prior to the eighteenth century.
He mentions Galen who asks readers to "think first, please, of the man's [external genitalia] turned in and extending inward between the rectum and the bladder.
[16] In the two-sex model though, these experts wanted to create a link between biological sex and theoretical gender and anything transgressing these boundaries was seen as being abnormal.
[18] The subordination of women by men began with the hierarchical ordering of their bodies and ended with their firmly defined gender roles.
Anatomist and physician Andreas Vesalius, represented women's organs as versions of man's in all three of his influential works.
[35] It was thought that both males and females experience an orgasm during intercourse and that both released some sort of fluid, which would mix together and the two emissions would result in conception.
[35] Under the economy of bodily fluids, the presence of both male and female seed and orgasms points to a sexless conception of libido that fits in a one-sex model.
[36] Laqueur notes that "the fact that women had gonads like men, that they had sexual desires, that they generally produced fluid during intercourse and presumably showed signs of 'delight and concussion', all confirmed the orgasm/conception link.
"[33] In Laqueur's one-sex model, the exception to this orgasm-conception link is Aristotle, who sought to separate orgasm from conception to preserve his asymmetrical view of men as providing the "efficient cause" and women the "material cause" during generation.
[45] However, Laqueur claims that scientific advances in the eighteenth century had little to do with the declining importance of the female orgasm to conception, or more generally, with the shift to the two-sex model.
"[52] He sees the clitoris as being "the organ through which excitement is transmitted to the 'adjacent female sexual parts' to its permanent home, the true locus of a woman's erotic life, the vagina.
He says that "whenever a woman is incapable of achieving an orgasm via coitus, provided the husband is an adequate partner, and prefers clitoral stimulation to any other form of sexual activity, she can be regarded as suffering from frigidity and requires psychiatric assistance.
"[56] The vagina on the other hand was seen as "a far duller organ" and "only the glands near its outer end are relevant to sexual pleasure because they pour out great quantities of a saline liquor during coitus, which increases the heat and enjoyment of women".
"[58] Scholars such as Katharine Park, Robert Nye, Helen King, Joan Cadden, and Michael Stolberg have criticized Laqueur's theory on the grounds that his described shift from one-sex to two-sex does not reflect a thorough reading of historical sources.
According to Park and Nye, Laqueur synthesizes conflicting accounts of sex and anatomy by Aristotle and Galen in order to craft the impression of a uniformly accepted one-sex model prior to the eighteenth century.
[59] In Park and Nye's account, Laqueur mistakenly takes early anatomists' comparisons between male and female genitalia as evidence that, in their view, “the vagina really is a penis, and the uterus is a scrotum.”[60][61] Park and Nye also remark that Laqueur does not locate the historical evidence he uses within culturally and historically specific definitions of sex; instead, he uses it out of context to fit a modern understanding of sex and gender.
[62] In particular, Laqueur reduces the metaphysical distinctions Renaissance philosophers made between men and women to sociological categories of gender, while still maintaining that there must have only been one anatomical sex.
[62] King echoes Park and Nye in the claim that the one-sex and two-sex models seem to have coexisted throughout history, and were not segregated by era as Laqueur suggests.
She writes that the theories in Making Sex are appealing because Laqueur conceptualizes a simple chronological narrative of his one-sex and two-sex models, even at the cost of historical context and nuance.
[64] The use of these models creates a static perception of the period, damaged by arbitrary divisions of 'before' and 'after' that were not relevant to people at the time.
[65]: ix–xi Stolberg provides evidence to suggest that significant two-sex understandings of anatomy existed before Laqueur claims, arguing that sexual dimorphism was accepted as early as the sixteenth century.
He also argues that differences between the sexes were accepted in the early modern period under the proviso that woman's biology was fit for purpose, i.e., motherhood.
[66]: 298 Further, Stolberg contests Laqueur's claim that sexual dimorphism arose merely in response to Enlightenment ideals of equality, as a means of keeping women insubordinate.
[67] Joan Cadden has pointed out that 'one-sex' models of the body were already treated with scepticism in the ancient and medieval periods, and that Laqueur's periodisation of the shift from one-sex to two-sex was not as clear-cut as he made it out to be.