I'm not sure what you mean by "current consensus" on the one-sex theory. Yeah, modern medicine is pretty damn clear that the uterus is not an inverted penis, and cissexual women are not cissexual men who just didn't develop all the way. I do think growing awareness of/research into intersexuality on a physical, emotional, chromosomal, etc level has the future potential to reshape how we think about sex and sex identity, but this is AskHistorians. So:

Laqueur has been very influential, and his idea (building on Judith Butler) that sex as well as gender is historically contextualized is really insightful and important. But when it came to actually doing the contextualizing, Laqueur messed up.

You see, he pretended the Middle Ages didn't exist. This neglect, intentional or not, goes on to color and distort his understanding of the early modern era as well.

Laqueur's one-sex model is predicated on one section in one text by late antique medical writer Galen, in which Galen describes assigned-female (I will hereafter just use female and male for simplicity) reproductive organs as male reproductive organs flipped inside out and into the body. (The idea of women as "failed men" comes from Aristotle and is not the focus of Laqueur's argument.) Now, Galen was an enormously important medical authority for medieval writers in both the Arabic and Latin traditions.

But the reception of this particular passage in On the Use of Parts is...iffy.

In Arabic writing, this particular idea of Galen's gets picked up most importantly by Avicenna (Ibn Sina) in his Canon, which will go on to enjoy strong reception in the Latin West. Razis (al-Razi), another favorite Muslim physician of western thought, seems to alude to the idea when discussing treatments for problems with sexual intercourse ("problems" being male homosexuality). As Katharine Park points out, Al-Majusi actually cited Galen's other writing when relating the uterus to the bladder rather than an inverted penis.

Despite access to the ideas, however, Latin and eventually European vernacular traditions of the Middle Ages give one-sex theory surprisingly little airtime. That passage in the original Galen doesn't appear in surviving western texts until the very tip-top end of the fifteenth century. And while Laqueur makes a big deal of the lack of a word for "vagina" in the premodern west, writers had absolutely no trouble talking in terms of wombs and emphasizing the uniqueness and unique functions of the uterus. In fact, pregnancy and menstruation are pretty much the obsessions of premodern gynecology, such as it exists, beyond a few texts like the Trotula.

There is absolutely no hegemony of a "one-sex" theory in medieval western medical thought. Joan Cadden has very politely debunked Laqueur's monolith as mythology and demonstrated the messiness of medieval medical theories of sex (Park, on the other hand, has no time for him). Even the appearance of inside-out genitalia theory in the 16th century has to do first of all with the Renaissance European obsession for all things classical, but also to a general guide for surgery students to envision anatomy as well as to the encroachment of authoritative male writers and physicians over gynecology and obstetrics. (It's not until the brink of the early modern era that there was any kind of societal comfort with male doctors viewing women's genitalia even for treatment purposes--and this is fascinating timing, because this time period is generally associated with exactly the opposite sort of movement, towards increasing opprobrium towards violation of strict sexual mores).

The early modern era also pays a lot more attention to sodomy, which is the unmentionable sin or the "silent sin" in the Middle Ages. In particular, sodomy becomes viewed as a violation of sex/gender norms that, in this era, were increasingly important as the nuclear family became THE bedrock ordering unit of a society obsessed with right order. The "done unto" partner in a male homosexual sex act; the "doing unto" partner in a female homosexual sex act--they get described as "the woman" "like a man" in court records. But that's with the stricter 'rules'/norms of the early modern era.

And even in the Renaissance, I think, we can see some hesistation with a strict anatomical equivalence of inverted southern-region genitalia. Rather, there's an almost metaphorical sense of drawing parallels. Jutta Sperling and Barbara Orland have talked about then, well, the penis-ification of descriptions of women's breasts in early modern Europe. Medieval rhetoric tended to see breast milk either in terms of charity and generosity (the Madonna lactans or Mary breastfeeding is a major symbol in medieval iconography) or for its role in the formation of the fetus (yes, while still in the womb). Early modern scholars, on the other hand, were likely to observe things like nipples becoming erect like a certain male member was wont to do. So even in an era whose medical texts did propagate a Galenic "inside-out" understanding of female genitalia, the overall understanding was by no means so straightforward.

But all of this that I've described above still operates within Laqueur's paradigm. And this in and of itself is a major problem. F or all his valiant and well-intentioned attempts to historicize the concepts of sex and gender (which is excellent and necessary), his concept of sex is entirely and thoroughly modern. For Laqueur, cultural/biological ideas of "sex" are defined by medical writing, by physicians and natural philosophers. That is not to say he thinks sex "is biological"; he's very Butlerin in arguing it too is culturally constructed. Rather, he assumes that sex is culturally constructed through medical/philosophical thought.

And in the Middle Ages, that is so not even close to the whole story. Literary scholars like Derek Neal have pointed to the role of romances and manuals of chivalry in shaping ideas of sex and gender roles especially among the nobility and eventually urban bourgeoisie. Even more important, and more accessible to the average medieval person, was the influence of religion. And as the Church made control of marriage and sexuality a major prong in its move to assert power over Latin society as a whole, canon law and pastoral care, along with "popular" religious writings like hagiography, became key propagators of ideas of sex and gender. (For example, the persistent link between women and infertility, or the gradual shift in adultery prosecutions from primary focusing on women to primarily targeting men).

Laqueur, as I mentioned, is absolutely right that we must historicize ideas of sex, gender, and the relationship between the two. For example, medieval scholars will talk about the "feminized Christ" of the late Middle Ages, such as Caroline Walker Bynum's descriptions of late medieval Christ as "open, bleeding, flowing, wounded"--characteristics that seem to get at 'sex' as well as 'gender'. But while this Christ may take on certain female and feminine characteristics, there's no question that he is a he. Medieval mystics envision themselves drinking blood from Christ's side wound in a facsimile of breastfeeding (...roll with it), at the same time holy women like Margaretha Ebner will miraculously breastfeed an envisioned infant Christ. Male mystic Meister Eckhart built on a looong Christian tradition of "giving birth to God/Christ in the soul"; female visionary Christine Ebner (no relation to Margaretha) experienced a mystical "quasi-physical" pregnancy with an envisioned Christ.

And late antique/medieval Christianity well nurtured the ideological concept, linked to the Aristotelian notion of women as men who stopped developing in the womb a bit to early, of the "virile woman." That is, if a person acting really awesome happens to be female, she has "become a man." Early Church martyr and excellent woman writer Perpetua has a dream of herself in the arena a few days before her execution ad bestias, in which she is actually male. And yet medieval women--including some who sometimes claim the power that lies in virility--also assert their "female weakness" as its own show of paradoxical strength and authority. Medieval ideas about sex and gender and the relationship between the two are trippy and misogynist and weird and fascinating.

But they are far more diverse than Laqueur's one-sex model implies. And even more crucially, unlike his assumption that nothing happened between Galen and 1700, they existed in the first place.