Skeletal Studies Show Sex, Like Gender, Exists Along a Spectrum

By Alexandra Kralick | November 16, 2018 1:27 pm
Stanislawa Walasiewicz

Stanislawa Walasiewicz won the gold for Poland in the women’s 100-meter dash at the 1932 Olympic Games. Upon her death, an autopsy revealed that she had intersex traits. (Credit: Wikipedia)

She wasn’t especially tall. Her testosterone levels weren’t unusually high for a woman. She was externally entirely female. But in the mid-1980s, when her chromosome results came back as XY instead of the “normal” XX for a woman, the Spanish national team ousted hurdler María José Martínez-Patiño. She was ejected from the Olympic residence and deserted by her teammates, friends, and boyfriend. She lost her records and medals because of a genetic mutation that wasn’t proven to give her any competitive advantage.

People like Martínez-Patiño have been ill-served by rules that draw a hard line between the sexes. In the U.S., the Trump administration looks set to make things worse. According to a memo leaked to The New York Times in October, the U.S. Department of Health and Human Services is trying to set up a legal binary definition of sex, establishing each person “as male or female based on immutable biological traits identifiable by or before birth.” But our bodies are more complicated than that.

An increasing recognition of this complexity by researchers and the public has affirmed that gender sits on a spectrum: People are more and more willing to acknowledge the reality of nonbinary and transgender identities, and to support those who courageously fight for their rights in everything from all-gender bathrooms to anti-gender-discrimination laws. But underlying all of this is the perception that no matter the gender a person identifies as, they have an underlying sex they were born with. This represents a fundamental misunderstanding about the nature of biological sex. Science keeps showing us that sex also doesn’t fit in a binary, whether it be determined by genitals, chromosomes, hormones, or bones (which are the subject of my research).

The perception of a hard-and-fast separation between the sexes started to disintegrate during the second wave of feminism in the 1970s and 1980s. In the decades that followed, we learned that about 1.7 percent of babies are born with intersex traits; that behavior, body shape, and size overlap significantly between the sexes, and both men and women have the same circulating hormones; and that there is nothing inherently female about the X chromosome. Biological realities are complicated. People living their lives as women can be found, even late in life, to be XXY or XY.

Skeletal studies, the field that I work in as a doctoral student in anthropology, and the history of this field show how our society’s assumptions about sex can lead to profound mistakes, and how acknowledging that things are not really as binary as they may seem can help to resolve those errors. Trump and his advisers should take note.

If you’ve ever watched the TV series Bones, you’ve heard Temperance “Bones” Brennan, the show’s protagonist and star forensic anthropologist, call out to her colleagues whether the skeleton she’s analyzing is male or female. That’s because sex distinctions are very helpful to know for missing persons and archaeological sites alike. But just how easy is it to make this determination?

In the early 1900s, the U.S.-based anthropologist Aleš Hrdlička helped to found the modern study of human bones. He served as the first curator of physical anthropology at the U.S. National Museum (now the Smithsonian Institution). The skeletons Hrdlička studied were categorized as either male or female, seemingly without exception. He was not the only one who thought sex fell into two distinct categories that did not overlap. Scientists Fred P. Thieme and William J. Schull of the University of Michigan wrote about sexing a skeleton in 1957: “Sex, unlike most phenotypic features in which man varies, is not continuously variable but is expressed in a clear bimodal distribution.” Identifying the sex of a skeleton relies most heavily on the pelvis (for example, females more often have a distinctive bony groove), but it also depends on the general assumption that larger or more marked traits are male, including larger skulls and sizable rough places where muscle attaches to bone. This idea of a distinct binary system for skeletal sex pervaded—and warped—the historical records for decades.

pelvis gender difference

Two pelvises with drastically exaggerated differences—a man’s shown on the left and a woman’s on the right (identified in Lithuanian)—illustrate how sex was estimated skeletally in the early 1900s. (Credit: Henry Gray/Wikimedia Commons)

In 1972, Kenneth Weiss, now a professor emeritus of anthropology and genetics at Pennsylvania State University, noticed that there were about 12 percent more male skeletons than females reported at archaeological sites. This seemed odd, since the proportion of men to women should have been about half and half. The reason for the bias, Weiss concluded, was an “irresistible temptation in many cases to call doubtful specimens male.” For example, a particularly tall, narrow-hipped woman might be mistakenly cataloged as a man. After Weiss published about this male bias, research practices began to change. In 1993, 21 years later, the aptly named Karen Bone, then a master’s student at the University of Tennessee, Knoxville, examined a more recent dataset and found that the bias had declined: The ratio of male to female skeletons had balanced out. In part that might be because of better, more accurate ways of sexing skeletons. But also, when I went back through the papers Bone cited, I noticed there were more individuals categorized as “indeterminate” after 1972 and basically none prior.

Allowing skeletons to remain unsexed, or “indeterminate,” reflects an acceptance of the variability and overlap between the sexes. It does not necessarily mean that the skeletons classified this way are, in fact, neither male nor female, but it does mean that there is no clear or easy way to tell the difference. As science and social change in the 1970s and 1980s revealed that sex is complicated, the category of “indeterminate sex” individuals in skeletal research became more common and improved scientific accuracy.

For generations, the false perception that there are two distinct biological sexes has had many negative indirect effects. It has muddied historical archaeological records, and it has caused humiliation for athletes around the globe who are closely scrutinized. In the mid-1940s, female Olympic athletes went through a degrading process of having their genitals inspected to receive “femininity certificates.” This was replaced by chromosome testing in the late 1960s and subsequently, hormone testing. But instead of rooting out imposters, these tests just illustrated the complexity of human sex.

It might be more convenient for the U.S. federal government to have a binary system for determining legal sex; many U.S. laws and customs are built on this assumption. But just because it’s a convenient system of classification doesn’t mean it’s right. Some countries, such as Canada, and some states in the U.S., including Oregon, now allow people to declare a nonbinary gender identity on their driver’s license or other identification documents. In a world where it is apparently debatable whether anti-discrimination laws apply to sex or gender, it is a step in the wrong direction to be writing either one into law as a strictly binary phenomenon.

The famous cases of strong, athletic, and audacious female athletes who have had their careers derailed by the Olympic “gender tests” exemplify how misguided it is to classify sex or gender as binary. These women are, like all of us, part of a sex spectrum, not a sex binary. The more we as a society recognize that, the less we will humiliate and unnecessarily scrutinize people—and the less discriminatory our world will be.

Alexandra Kralick is an anthropology Ph.D. student at the University of Pennsylvania.

This article originally appeared on SAPIENS.

CATEGORIZED UNDER: Health & Medicine, Living World
  • Uncle Al

    A hyphenated anthropologist? Talk with Jamie Lee Curtis about testicular feminization or George Washington about Klinefelter’s syndrome.

  • Frank R Nicholas

    Another PhD student down the drain.

  • Kris Shaw

    So the fact that bone structure varies continuously, such that sometimes it is difficult to classify a skeleton as male or female, counts as evidence that sex is non-binary? That is equivalent to saying that sex is a spectrum because some women are taller than men.

    • Captain Obvious

      Read the entire article. Skeletal ambiguity was only an early indicator of possible non-binary sex. DNA testing shows that there are people who don’t one or the other types of chromosones.

      • Kris Shaw

        Sex is a classification system for reproductive function, of which there are two.

        • Captain Obvious

          No argument with that. Just pointing out that bone structure wasn’t cited as proof of non-binary sex.

          • Kris Shaw

            Touche. The text uses the skeletal studies more as metaphor than evidence. I should have been more precise.

            Of course, the title is a little less metaphorical.

  • An Educated Person

    I shouldn’t be surprised that there are ignorant and uniformed comments here. Why are you people even reading this website? Go back to Fox News, your right-wing conspiracy wonks, or your other fairy tale mongers.

    • Orion

      As an educated person you should be able to recognize bias in research. This article provides evidence for nothing outside of indiscriminate pelvis sizes. It is quite a jump to say this makes gender fluid. It does show we shouldn’t determine results by a single factor. In truth there is very little evidence for gender fluidity. There are outliers, as there are in most inquiries. It is not hurtful to state facts, unless stated hurtfully.

      • Kevin Mc

        Please reread the article, your bias is showing. The article in fact DOES provide evidence for many things outside of pelvic sizes. The author studies bones, as was clearly stated and therfore, that is the focus of her article.

        • Orion

          Hi, Kevin- Facts are not biased. You have no idea what my personal thoughts are, but because I disagree with the article, you think you do. Science, as the article DOES demonstrate, can be biased. The author shows the bias (from the old-guard scientific community) in determining male/female genders based on pelvic sizes. That is clear and not in debate. The author then makes the leap that this is evidence for gender fluidity. Do you think she has evidence for this? That is where she brings her own bias in. Unless there is something testable and verifiable in the makeup of the bones that clearly shows that gender is fluid, she should not make this leap. People, male and female, have different pelvis sizes. Wow. That has nothing to do with gender outside of how we determine sexes from skeletal remains. Those are all facts. No bias inserted.

          • Kevin Mc

            You’re right, the pelvis size has nothing to do with gender, nor does anthing else in the article. It discussed sex, not gender. Also science IS NOT biased, although some interpretations may be.

  • John Do’h

    Just curious, as far as a sexual “binary” view, how many individuals cannot potentially either fertilize an egg or have an egg to be fertilized? What percentage cannot have children because of their sexual “fluidity”?

    This is a very difficult issue, and many do not want to deal with it, but you have to realize that the majority of these gender “non-binary” people have been heavily abused and demeaned since very young as being worthless individuals, failures at being a male or female. I know that they do not want to called “crazy” but there are serious mental illness issues because of how they have been treated throughout their life. Continuing to demean and oppress these people just hurts them and helps no one.

  • Scott S.

    One must keep in mind we are discribing two complete different systems here – biological and legal. While the author makes a great case for spectrum analysis of sex in the bones, it does not take note that the U.S. legal system is binary, as iare all legal systems. Either something is, or is not legal. Also, what seems to be lost is proportionality in discussing outliers. The legal system, at least in America, is focused on codes and laws formed by majorities, sans 50.1% and above. Outliers, as the authur describe generally are not statiscially significant. This sets up the contrast between the systems. Do you make law based upon statistically insignificant samples from science, the outliers, or do you make laws and policies based upon republican representative principles upon which our country and its undisputed greatness are founded upon? No law is perfect, nor has perfect application. This is why the judicuary is a co-equal branch to examine and sort the outlier cases.

    • Amy Eyrie

      The best science available is a determining factor in all courts and court decisions. Totalitarianism, which is what Trump is attempting to practice, attempts to take an opinion and make it into a law. The vast American public is not voting on the idiotic, anti-science, defilement of the system being perpetrated by Trump. That’s why the democrats just swept the elections, because Trump has already spiraled off lunacy.

      • Dirk Diggler

        Seriously; the Democrats swept the elections? People like you are so deluded that you are unable to grasp simple mathematics, and yet you proclaim to know something about science.

        Moreover, can you explain to me—and anybody reading these comments—exactly how the left, at the behest of their corporate overlords, is fighting against totalitarianism?

        Now tis will be the most difficult part for you: Try using actual evidence and facts—emotions DO NOT count. Go it snowflake?

  • SuzyQue

    Finding exceptions to the rule doesn’t disprove the rule itself.

  • Adam Darwin

    Gender isn’t a spectrum, it’s a bimodal distribution.
    Whether bones fit that pattern or not depends on the data, but I highly doubt that their sizes are a spectrum. There should be a mean at which males and females aggregate with a standard distribution.
    That wouldn’t be a spectrum, again: bimodal distribution.
    An evenly-distributed spectrum in terms of gender would look ridiculous. You would see men with breasts and wide hips, and women with wide shoulders and beards. You wouldn’t be able to tell who is who, because there wouldn’t be any clustering in the appearance of bodily features.
    It is also getting it kind of backwards to state that “Skeletal Studies Show Sex, Like Gender, Exists Along a Spectrum” – gender itself is the aggregate of clustered features, and skeleton dimensions are a part of that, so gender and skeletons aren’t separate from each other. It’s a bit like saying “cities, like countries, have size”. One is a part of the other…
    “Science keeps showing us that sex also doesn’t fit in a binary, whether it be determined by genitals, chromosomes, hormones”
    The definition of sex is that you have one reproductive organ system or another. Penis and testicles or vagina, ovaries and uterus. If you have the former you’re male, latter you’re female. Simply the fact that some people have some parts of the others or something in between doesn’t mean that sex is a spectrum, it simple means there’s exceptions / intersex, the binary definition is still valid.

    • Kevin Mc

      Where to start? First paragraph, it IS a spectrum, so you are wrong.
      Second paragraph, there ARE men with breasts and women with bears, so you are wrong again, again it IS a spectrum.
      Please actually READ before posting your opinions as facts!

      • Adam Darwin

        Do you see the same number of men with breasts as women and the same number of women with beards as men? No. So NOT a spectrum. That’s what a spectrum would look like and that’s not what gender looks like, it’s a distribution.

        • Kevin Mc

          You don’t understand what the word spectrum means, do you? It DOES NOT mean an equal number! It means a variation from one end to the other. Please actually look up the meaning of the words before telling someone they are wrong.

          • Adam Darwin

            The word spectrum was originally used by scientists to describe how white light divides evenly into different colors. That’s not what happens with gender-distributed traits. You can say it’s a spectrum, but it is more precise to call it a bimodal distribution.

          • Kevin Mc

            It may have been originally used that way, but it is not currently used that way, for instance people on tbe autism spectrum, are not evenly distributed, and that’s how the author used that term.


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