BABAO Statement on Sex Estimation

Statement of Purpose

In the month of July, a number of articles were published online, primarily from politically right-wing American-based newspapers, with headlines claiming that LGBT [Lesbian, Gay, Bisexual, and Transgender] activists are pushing for archaeologists to stop assigning labels of male and female to human remains. In these articles, the authors misuse and misrepresent the writing (published research and social media posts) of students and academics working in archaeology who are engaging in constructive theoretical debates around topics of biological sex and/or gender identity in osteoarchaeology [the study of human skeletal remains] or forensic anthropology [the application of the study of human skeletal remains to forensic contexts]. It is important to note two things before proceeding:

1. Gender identity and biological sex, though related, are not synonymous for each other and are treated as such throughout this statement. 
2. There is no organised campaign within the LGBT rights movement focussed on stopping osteoarchaeologists/forensic anthropologists from labelling human remains as male or female.
3. The language used to discuss and describe biological sex and gender identities is constantly evolving as people examine these topics at a personal, community, and/or conceptual level. As such BABAO acknowledges that the language used in this statement is representative of when this statement was written and may not remain in current or common usage. 

The purpose of this brief statement is to present BABAO’s response to these articles by explaining how archaeologists, primarily osteoarchaeologists, engage with the topics of biological sex and gender identity in human remains. 

What is biological sex?

Biological sex is determined by differences between individuals at many levels of their biology, from their outward physical appearance, their internal anatomy and sex organs, their unique hormonal makeup, and their genetics and chromosomes. In the majority of the human population, an individual’s sex chromosomes will align with the other biological levels where sex-based differences appear. This can be seen as an individual with XX chromosomes having biological traits that are considered to be female, and an individual with XY chromosomes having biological traits considered to be male. 

At birth, sex is typically assigned by doctors based on the outward appearance of a baby’s genitalia: however, as discussed above, biological sex is more complex than this, and an individual may exhibit some traits commonly considered to be female, some commonly considered male, and some atypical from either. Individuals who show these combinations of biological traits, which can occur across all levels of human biology, are intersex. However, some intersex variation may not affect an individual’s outward appearance, so it is possible for an individual to be unaware of being intersex, and to consider themselves biologically male or female due to how their body has developed.

What is gender? 

Gender is a set of socially constructed norms, behaviours, and roles that are most commonly associated with being male or female. Both in the past and the present gender is frequently conflated with biological sex. Historically, religions and societies which are patriarchal have taught and reinforced a gender binary of male and female. European colonialism and missionary work often forced this view onto Indigenous cultures, leading to the persecution of those with more complex gender identities who fell outside of the coloniser’s perceived sex=gender binary.

In the modern western world, individuals whose gender does not align with their biological sex may choose to identify as transgender or trans. They may identify with the male, or female gender, or even between or outside of this binary. Individuals from non-western cultures may choose to identify as trans or may have their own gender categories which they identify with instead. There are many examples, both in the modern world and in the past, of communities of individuals whose gender identity falls outside of the male and female binary, such as Mexico’s “Muxe”, India’s “Hijra”, or the Ancient Roman “Galli”. 

Biological sex and gender identity in archaeology

When examining biological sex and gender identity in archaeology we are constrained to the skeletal remains of individuals and the manner in which they were buried (i.e., where and how they were buried, were they buried with objects and where were these placed, etc.) The information we can gain from this is important, but it is limited. 

When working with human remains, osteoarchaeologists have begun to emphasise the limitations of their methods by using terms such as estimated sex or skeletal sex rather than biological sex. This is because the skeleton is only one part of the human biology where sex differences occur, and archaeologists rarely have access to soft tissues, DNA, or other chemical data which could provide additional insights into an individual’s sex. Additionally, sex assessment is inaccurate for skeletal individuals who died before going through puberty, as puberty is when hormonal changes drive the development of the many physiological differences between biologically male and female individuals. As such, it is difficult – if not impossible – to assess sex from the skeletons of infants and children without using genetic or other chemical analyses. 

A large range of methods have been developed to allow osteoarchaeologists to identify skeletons which are more female or male in their physical shape. Some parts of the skeleton are more reliable than others as a result of their form and function. For example, the shape of the pelvis and skull are highly related to an individual’s sex. There are also some parts of the skeleton that show little difference between the sexes and so are not reliable indicators of sex (such as the vertebrae, hands, and feet). All the skeletal traits used by osteoarchaeologists to assess an individual’s sex exist on a continuum between an extremely male presentation and an extremely female presentation, with more indeterminate presentations existing in the middle (Fig 1.). 

Figure 1.The standard stages for scoring the greater sciatic notch within the pelvis (indicated by the arrow). With the trait moving from a wide notch (female: score 1) narrowing through an indeterminate sex (score 3) to a small notch (male: score 5). After White and Folkens (2005).

It is possible for different parts of the same skeleton to appear more female or more male than other parts, due to the skeleton’s reaction to disease, physical exercise, ageing, etc. Because the development of the skeleton is driven by a range of factors, not simply an individual’s genetics, there is also variation both geographically and chronologically in how much an individual, and whole cemetery populations, may develop more extreme expressions of sexual skeletal variability. When a complete skeleton is available to study, the osteoarchaeologist will consider as many traits as possible to decide on an individual’s skeletal sex. The accuracy of this assessment may be as high as 95%. However, when skeletons are incomplete or poorly preserved, fewer or less accurate traits may have to be used, and the confidence in the final sex assessment will be low. As such, it is common in osteological reports to include a range of categories for sex such as “male”, “probably male”, “sex unknown”, “probably female”, and “female” to consider the degree of uncertainty that is present in these methods, and to reflect individuals for whom it isn’t possible to estimate sex based on their skeleton.  

The development of biomolecular methods within archaeology has created two new ways to provide information about a skeletal individual’s sex chromosomes. The study of ancient DNA (aDNA) allows geneticists to identify the sex chromosomes of an individuals. There are cases where this may contradict the estimated sex of the individual based on osteological analysis or identify intersex individuals. The study of peptide (proteins) in tooth enamel has allowed archaeologists to test for the presence or absence of a “Y” sex chromosome. This method may be used where aDNA has not been preserved in the skeleton and is a less destructive or expensive method compared to aDNA analysis. However, both of these methods have limits in what they can tell us, and are open to risks such as sample contamination (aDNA only) or analytical error (both methods), which may lead to false results. 

Information regarding the gender identity of excavated individuals is frequently very limited. In rare cases, archaeologists may encounter individuals buried with identifying information such as a gravestone, burial monument, or coffin plate, which identifies them by a name we know was gendered by their society. However, it is likely a grave marker would reflect an individual’s public identity, and may not represent their personal gender identity. 

Grave goods have been widely used by archaeologists to infer gender identity, although the difficulties of doing this have not always been fully appreciated. While certain objects may have been associated with gender identities in the past, it is easy to project modern day gender norms onto grave goods. A good example of this appears within Viking/Scandinavian studies, where early 20^th– century European archaeologists initially assumed that individuals buried with swords were warriors and therefore male, as being a soldier was associated with men in the archaeologist’s own culture.  Through the re-examination of these remains, using both skeletal and, in some cases, aDNA evidence, it has been shown that some individuals buried with swords were biologically female or, in one case, intersex. However, we do not know how exactly these individuals would have described their own gender, but these examples demonstrate the complex interplay between an individual, their sex, gender, how they were buried, and what this might tell us about how they lived. 

The identification of trans, or gender non-conforming, individuals from their skeletons is highly limited. It may be possible to identify archaeological individuals who appear to be skeletally male, but their burial appears typical for a female gendered individual. But these interpretations are limited by archaeologists’ own cultural perceptions, our often-limited knowledge of how past cultures and societies may have viewed, expressed, and discussed gender diversity, and our inability to accurately know how skeletal individuals personally identified. For modern trans individuals encountered in forensic cases, there may be indicators present that imply a possible trans identity (personal effects, clothing associated with a specific gender, surgical implants), however what evidence may be available from the skeleton itself is not well understood. Within the current suite of gender affirming surgeries available to trans individuals the vast majority are focused on soft tissues. Facial surgery is something which some individuals may choose to have, with portions of the nose or jaw/chin being surgically altered into shapes that are deemed to be more typically masculine or feminine. However, many of these plastic surgeries, both skeletal and soft tissue, are not exclusively performed on trans individuals, so they cannot be taken as a definitive sign of trans identity. Additionally, it is currently unknown what the long-term effects of puberty blockers and hormone replacement therapy are on the skeletons and general physiology of trans individuals. As such, it is going to take time for forensic anthropologists to create methodologies that are inclusive of trans individuals. 

In summary, osteoarchaeologists and forensic anthropologists have to consider both the biological sex and gender identity of an individual. As such, these professionals understand that biological sex exists on a spectrum, of which skeletons and the sexual variation they show is only one part of a greater whole. They also understand that the assessment of sex using skeletons is not 100% accurate and this analysis may not align with an individual’s biological sex or gender identity. By remaining conscious of this uncertainty, osteoarchaeologists and forensic anthropologists work to encompass the complexities of societal structures and identities attested to in written and oral histories and mythologies, whilst also benefiting modern society and families through individual identification following mass casualty events, missing persons cases, or homicides. 

References

Adams, D., Goldstein, J., Isa, M., Kim, J., Moore, M., Pilloud, M., Tallman, S., and Winburn, A. 2022. A conversation on redefining ethical considerations in forensic anthropology. American Anthropologist. Volume 124 Issue 3 Pages 597-612.

Agarwal, S., and Wesp, J. (editors) 2017. Exploring sex and gender in bioarchaeology. University of Albuquerque. New Mexico Press.

Astorino, C. 2019. Beyond Dimorphism: Sexual Polymorphism and Research Bias in Biological Anthropology. American Anthropologist. Volume 121 Issue 2 Pages 489-490. 

Garofalo, E., and Garvin, H. 2020. The confusion between biological sex and gender and potential implications of misinterpretations. In: Klales, K. (editor) Sex estimation of the human skeleton: History, methods, and emerging techniques. London. Academic Press. Pages 35-52.

Geller, P. 2017. The Bioarchaeolgy of Socio-Sexual Lives: Queering Common Sense about Sex, Gender, and Sexuality. Switzerland. Springer.  

Hedenstierna-Jonson, C., Kjellström, A., Zachrisson, T., Krzewińska, Sobrado, V., Price, N., Günther, T., Jakobsson, M., Götherström, A., and Storå, J. 2017. A female Viking warrior confirmed by genomics. American Journal of Physical Anthropology. Volume 164 Issue 4 Pages 853-860. 

Mendoza-Álvarez, C. and Espino-Armendáriz, S. 2018. A Critical Approach to Gender Identities in the “Muxe” case. Humanities and Social Sciences. Volume 6 Issue 4 Pages 130-136.

Moilanen, U., Kirkinen, T., Saari, N-J., Rohrlach, A., Krause, J., Onkamo, P., and Salmela, E. 2021. A Woman with a Sword? – Weapon Grave at Suontaka Vesitorninmäki, Finland. European Journal of Archaeology. Volume 25 Issue 1 Pages 42-60.

Mowat, C. 2021. Don’t be a Drag, Just be a Priest: The Clothing and Identity of the Galli of Cybele in the Roman Republic and Empire. Gender and History. Volume 33 Issue 2 Pages 296-313.

Schall, J. Rogers, T. and Deschamps-Braly, J. 2020. Breaking the binary: the identification of trans-women in forensic anthropology. Forensic Science International. Volume 309 Article 110220.

Sofaer, J. 2006. Gender, Bioarchaeology and Human Ontogeny. In: Gowland, R and Knüsel, C. (Editors) Social Archaeology of Funerary Remains. Oxord. Oxbow Books. Pages 155-167.

Stewart, N., Gerlach, R., Gowland, R., Gron, K., and Montgomery, J. 2017. Sex determination of human remains from peptides in tooth enamel. Proceedings of the National Academy of Sciences. Volume 114 Issue 52 Pages 13649-13654.

Tallman, S., Kincer, C., and Plemons, E. 2021 Centering transgender individuals in forensic anthropology and expanding binary sex estimation in casework and research. Forensic Anthropology. Volume 15 Issue 2 Pages 161-180. 

White, T., and Folkens, P. 2005. The Human Bone Manual. London. Elsevier Academic Press.