In January 2024, a eugenics-focused X account shared an image indicating that, over the course of the 20th century, human brains have grown larger. “There are certainly other factors at play,” wrote Elon Musk in reply, “but heavy use of c-sections allows for a larger brain, as brain size has historically been limited by birth canal diameter.” Musk reportedly asked Ashley St. Clair, one of the mothers of his many children, to have a scheduled c-section, presumably for this reason.
Implicitly referencing the dramatic rise of c-section rates over that same period, Musk’s statement also evoked the “obstetrical dilemma,” a phrase coined by anthropologist Sherwood Washburn in 1960. Writing about how the use of tools affected human evolution, Washburn posited that early humans adapted to the advantages of tool use by becoming bipedal: walking on two feet freed up the hands. At the same time, tool use also spurred selection for larger brains. And this, according to Washburn, was the dilemma: as hips narrowed to accommodate bipedalism, heads grew larger. Washburn argued that the evolutionary solution to this obstetrical dilemma was for babies to be born earlier in their gestation — in a state known as “infant altriciality,” or developmental immaturity — so that their heads would not grow too big to fit through the bony birth canal. It was this notion that Musk reflected, and distorted, when he spoke about the birth canal acting as a limit on brain size — with “brain size” being an elliptical stand-in for intelligence.
Washburn’s formulation has been criticized on both scientific and sociological grounds. Some researchers have proposed an alternate hypothesis positing that mothers’ metabolic rates play a greater role in limiting gestational time than the size of the birth canal. Feminist critics have attacked Washburn’s theory for suggesting that women’s bodies are somehow evolutionarily flawed. The notion of infant altriciality, these critics also argue, also helps naturalize a gendered division of labor, by suggesting that helpless infants require the freed hands of bipedal mothers to carry them (literally) through their early stages of dependency, prohibiting women from hunting, and effectively restricting their role to caretaking. Feminist and scientific critiques notwithstanding, the concept of the obstetrical dilemma continues to hold sway within the discipline of anthropology.
Yet long before Washburn put a name to the obstetrical dilemma, 19th-century anthropologists and obstetricians produced a voluminous literature intensely focused on the female pelvis. Ostensibly concerned with the problem of obstructed labor, medical men posited that there was something amiss with women’s bony birth canal, and they set out to look for definitive anatomical answers. Immersed in cultures of craniometry — that notorious pseudoscience driven by racism and eager to offer a “scientific” justification for slavery and white supremacy — obstetricians sought to quantify the problem of obstructed birth by measuring the pelvises of skeletons. In these efforts, they built a discipline known as pelvimetry, a computational biological science aimed at understanding who was likely to succeed in having a “natural” vaginal birth and who, due to her pelvic size or shape, would likely need surgical intervention.
In addition to measuring skeletons, 19th-century obstetricians built up their data sets by measuring living, pregnant people. For external measurements, they used a metal, compass-like tool known as a pelvimeter, which had been in use since at least the 18th century. To take internal measurements, they used their hands (until the advent of the internal pelvimeter). Judging external measurements to be “utterly worthless,” the prominent obstetrician and textbook author John Whitridge Williams wrote in his 1891 pamphlet “Pelvimetry for the General Practitioner” that only internal measurements produced accurate readings. Describing the technique, he wrote: “We attempt to reach the sacral promontory; and having reached it, we press the ulnar side of the tip of the middle finger against it and retain it in this position, while with the radial side of the same hand, we press hard against the lower margin of the symphysis.” The apparent accuracy and value of these internal measurements derived from the fact that they seemed to capture the all-important yet elusive diameter of the pelvic inlet.
The big-picture point of collecting all of this data was to derive a number that described the “normal” pelvis shape and size, or the size of the pelvic inlet that would almost certainly allow for an uncomplicated vaginal birth — and size or shape that would not. In this way, pelvimetry was meant to be a predictive science, allowing doctors to predict the course of patients’ labor before it even began. “With a pelvis of 5 ½ cm. (2 ¼ in.), we have an absolute indication for a Caesarean section,” wrote Williams. Such numbers would allow obstetricians to schedule c-sections long before their patients underwent an exhausting trial of labor and, Williams hoped, boost the United States’ lagging Caesarean success rate, whose inferiority (particularly compared to their “German confreres”) surely had to do with the fact that “most of our operations are done on exhausted or practically dying women who cannot be expected to recover.” Williams and others formulated another option for obstetricians to manage the births of women with contracted pelvises: inducing labor early, around 36 weeks, before the baby’s head became too big. In cases of truly contracted pelvises from, for example, rickets, surgical intervention saved many lives that would have otherwise been lost. Yet these schemes also foreshadowed and indexed the emergent paradigm in which all birth came to be seen as pathogenic and in need of medical management.
Pelvimetry, then, was one foundation in the edifice of medicalized obstetrics that was erected over the course of the 19th century in its march toward displacing traditional midwifery. But like much else in the history of medicine and obstetrics, it, too, was forged in racism and white supremacy. Beneath its computational superstructure lay the racist myth that African-descended women experienced less pain — and had an easier time in childbirth — than European-descended women. It was a myth that the Southern physician and slaveholder Samuel Cartwright had already attempted to codify when he invented the partly physiological, partly psychological condition of dysaesthesia aethiopica to describe what he perceived as laziness among enslaved people, which he attributed to a certain biological insensitivity of the skin. Cartwright’s compatriot John Van Evrie promulgated the myth that Black people’s nervous systems and skin were less physically sensitive and better able to tolerate pain in his 1853 pamphlet “Negroes and Negro ‘Slavery,’” writing that the “organic insensibility” of Black Americans made them “incapable of anticipating that terrible physical suffering from which the elaborate and exquisitely organized caucasian suffers” and, thus, “indifferent to the approach of death.”
This belief licensed and justified the heinous abuse and torture of enslaved people. When it entered the world of obstetrics, it manifested in the idea that Black and Indigenous people experienced less painful, even painless, births, that they experienced fewer complications in labor and delivery, and that they required surgical intervention less frequently. “Among primitive people, still natural in their habits and living under conditions which favor the healthy development of their physical organization, labor may be characterized as short and easy, accompanied by few accidents and followed by little or no prostration,” wrote the obstetrician George Engelmann in 1881. Engelmann supported his belief with anecdotes from his own experiences and those of his friends, who relayed to him stories of Indigenous women giving birth while out gathering firewood or hunting. According to a Dr. Faulkner, for example, one woman dropped back from her hunting party, dismounted her horse, laid down a blanket, and gave birth. Then she simply “wrapped up the young one in a blanket, mounted her horse, and overtook the party before they had noticed her absence,” Engelmann wrote.
To Engelmann and others, the ease of childbirth was directly correlated to a group’s degree of civilization. More “civilized” — white — people experienced far more suffering in childbirth. Working in the wake of Darwin and Spencer, some anthropologists and obstetricians imagined that the process of progressive evolution from ape to man played out on the female pelvis, just as it did on the infant head. They believed that as humans progressed toward civilization, female pelvises lost their ape-like qualities and gained their human shape. But for these men, this process was not consistent across racial groups: being further along down the path of evolution not only meant that a group was more civilized but that it was somehow more human, at a further remove from its ape ancestors. It was a cruel but noble irony of the process of evolution that greater refinement of the white woman’s pelvis was the source of her greater pain and suffering in childbirth. This pain was, in the words of the medical historian Miriam Rich, the “curse of civilization.”
Pelvimetry became a way to “prove” that the differential distribution of evolution’s refinements were built into and could be read in women’s anatomy and the anatomy of their infants. In his 1875 tract “On some of the Apparent Peculiarities of Parturition in the Negro Race,” Joseph Taber Johnson presented numbers aggregated from several of his colleagues’ skeletal measurements. His various caveats about sample size and contradictory analyses notwithstanding, Johnson nonetheless concluded that the data revealed that Black women’s pelvises were not more spacious, as he had expected in accordance with his beliefs about Black women’s lack of pain in childbirth. His numbers suggested that their pelvises were actually narrower. The perceived ease with which Black people gave birth could not be explained by a wider pelvic inlet, then. Johnson offered twin explanations supposedly supported by the data: that their pelvises were “degraded,” or further behind on the progressive road of evolution, and that their infants’ heads had a flattened “frontal bone and [low] development of the anterior cerebral lobes”: the scientific name of the racist trope for a sloping forehead. “The diminution of this diameter must lessen the difficulty in the passage of the foetal head,” Johnson wrote. He theorized that these two anatomical features — the “degraded” pelvis and the sloping forehead — were “harmonious,” co-evolved if less evolved, and that they facilitated those easy births that linked Black women more closely to their nonhuman ancestors than to her more fully human white counterparts.
Before long, obstetricians dabbling in biological anthropology would not only be measuring pelvises but typing them. In 1885, the Scottish obstetrician William Turner organized the world’s pelvises into three types: dolichopellic (deep pelvis), mesatipellic (medium pelvis), and platypellic (flat pelvis). According to Turner, flat pelvises, which gave the most trouble in childbirth, were the province of Europeans, and accounted for their more difficult and more dangerous births. Dolichopellic, or deep, pelvises were found among Africans and Polynesians — and also “present[ed] a closer approximation to the relative proportions of the parts found in the pelves of apes.” In the decades that followed, obstetricians continued to measure and organize pelvises by racial type. The 1930s saw the introduction of the Caldwell-Moloy classification system, with four types instead of Turner’s three, but with similar effect: obstetricians William Caldwell and Howard Moloy identified their newly named “anthropoid” pelvis, which “resemble[d] the long, narrow, oval pelvis of the anthropoid ape,” in 40.5% of the Black pelvises they measured but only 23.5% of the white. The Caldwell-Moloy classification system still appears in obstetric textbooks today, despite objections by some critics who point to the theory’s troubled origins as well as evidence that using these “artificial typologies” has not been shown to be clinically effective.
These medical men of the 19th and early 20th century did not use the phrase “obstetrical dilemma,” but they indeed were postulating one, telling a story of a dangerously tight fit between the birthing pelvis and the infant head. But mixed up as they were in the false notion that some races were “ahead” when it came to evolution and some “behind,” they also argued that white women were deeper in the dilemma than Black women: evolution produced in white women an even more treacherous, nearly impossible fit between their flatter, more fully human pelvises and their infants’ larger, superior heads and brains. Theirs was an obstetrical dilemma that only pertained to white women. To them, Black women had no such dilemma. Research has shown the persistence of these assumptions about Black birthing people’s tolerance for pain, and we continue to find evidence of racial bias in obstetrical practice and racial disparities in maternal mortality rates, where Black and Indigenous people are over three times more likely to die in childbirth than white people — a higher mortality rate that was the case in the 19th century, too, despite the conversation among white doctors and anthropologists about the ease of childbirth and safety for nonwhite people. Black birthing people and midwives voiced opposition to these assumptions, and continue to do so.
Musk’s post calls up the racist history of craniometry when it conflates and synonymizes head size, brain size, and intelligence, and it subscribes to the obstetrical dilemma even as it fantasizes about writing it out of human evolution by bypassing the birth canal altogether, at scale. The deepest premise of Musk’s post is that anatomy is destiny, where the body holds both the promise of some fantastical evolutionary leap (bigger brains) and is simultaneously limiting, inconvenient, and behind the times. But situating Musk’s post in this tradition of dehumanizing and pathologizing birthing people’s bodies also gives us an occasion to redefine the phrase “obstetric dilemma”: not as an evolutionary conflict of the human anatomy but as a man-made, historical conflict between these architectures of racism and sexism and the bodies of birthing people laboring under them.