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Osteology 101- Part 3/5: Sexing Skeletons

Sexing the skeleton might be a funny way of saying it, but it is a valid form of osteological analysis. Therefore, before we get into the nitty gritty, we need to establish the correct terminology to use. When estimating the sex of a skeleton, we use the term “sex”, which is not the same as “gender”. As was discussed in the first video of our Osteo 101 series, every skeleton can have characteristics that range between “male” and “female”. Therefore, when we discuss this topic, one should never use the term “gender”. To quote White and Folkens 2005, “[...] “sex” and “gender” have increasingly become conflated in the anthropological and medical literature. They do not refer to the same thing, they are not synonyms, and they should not be used interchangeably.” Having said that, we have now determined the importance of proper terminology. Thence, how do we determine the sex when confronted with human remains?

Sex identification on human remains is only possible when an individual has reached maturity. For Homo sapiens, that would be around 18+ years of age. If we are going to differentiate between male and female remains, the general consensus is that male remains are considered larger and more robust. Female remains are typically smaller in size and are not as rigid in the context of their morphology. When doing research on these kinds of sex-based characteristics, we are looking for sexual dimorphism. This defines a species with distinct different characteristics between sexes. Though an osteologist must pay heed to sex estimation on skeletal specimens from different populations. For example, some populations can have more robust skeletal morphology, and some can have lighter constructions. Regardless, the methods we use are relatively consistent.

Ward's Sherlock Bones instructions and pictures

Starting with the top of the skeleton, the skull. To estimate a sex from the crania, an osteologist will observe areas such as the glabella, the supraorbital ridge, the nuchal plane, frontal and parietal bossing, the external occipital protuberance, the mastoid and zygomatic process, the orbit shape, and the zygomatic arch extension. These terms may just look like jumbled letters, but essentially the osteologist will analyse the face, the region around the ears, and the back of the head. “Female” crania is softer in the context of robusticity. Therefore, the brow ridges (or supra-orbital ridge) will have a smaller slope. This single example can translate to most of the other aforementioned cranial areas in terms of a lighter construction. Otherwise, skeletal features such as the cheekbones (zygomatic process) will be thinner, and the protruding bit underneath the ears (mastoid process) will typically be smaller in size. “Male” crania will conventionally be more robust and rigid. The supra-orbital ridge- come on now, we know what it is- can protrude and have a steeper inclination. The additional areas we have discussed can be larger, relative to thickness and size. Further, mandibular traits, or the jaw bone, will share commonalities as in the crania. A “female” mandible will have a smoother slope at the gonial angle and mental protuberance. The gonial angle and mental protuberance are otherwise known as the part of the jaw on the side of the face (that we all choose to envy on models), and the chin. “Male” mandibles can be sharper and, again, more robust. That envy-worthy jaw line can flare out on “male” mandibles too, osteologically defined as the gonial eversion.

After an osteologist examines the skull, they will move to the pelvic traits. These observations are slightly more accurate because the human body must biologically consider reproduction. Human evolution relies on selective pressures to facilitate childbirth, and of course minimise mortality rate as a result. Therefore, “female” pelvic inlets are typically wider and more ovular. The greater sciatic notch (wherein with the sacrospinous ligament, this notch becomes an opening) would be wider as well. These areas allow for more space in a characteristically female pelvis. In general, the “female” pelvic girdle will therefore be broader. Characteristic male pelvic inlets are narrower, almost heart-shaped. The “male” pelvis as a whole is understood to be higher and narrower. Due to the mass of traits an osteologist will examine on the pelvis for sex estimation, we will save time- and your energy- with this general review.

As discussed in Video 1, an osteologist will analyse each individual trait and determine sexualization degrees with some gradable traits using methods recommended by the Workshop of European Anthropologists (WEA 1980) by dividing the sum of all scores multiplied by their weights by the sum of all weights. Many words, but it is simpler than it seems. Once a sum is determined between -2 to +2, the osteologist will mark the final sex estimation under one of five categories: Female, Probable female, Indeterminate, Probable male, and Male. Other traits that only entail their overall aspect are sorted into categories and averaged out. End result? Sex estimate!

Today’s video was heavier than the former, however, it is important for the interested reader to understand the differences between scientific and socially-constructed terminologies, and the results. It is virtually impossible to find a skeletal individual completely leaning into one direction on our sex estimation scale. In line with this, our skeletons are all a jumble of numerous characteristics that we, as humans, try to organise and categorise to enhance an understanding. Just like our aforementioned jumbled letters now create words we understand. Congratulations, you made it. Go forth with your newfound knowledge on sexing skeletons.

Thanks again to Jude to writing this piece and being the awesome lady that she is! Also huge thank you to Leiden University for letting us film at the Laboratory for Human Osteoarchaeology. For more information, click here to visit their website.

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