Quick Tips: How To Estimate The Biological Sex Of A Human Skeleton – Skull Method.

This is the 2nd blog post in this Quick Tips series on estimating the biological sex of human skeletal remains. If you haven’t read the first post on the basics of sexing skeletal remains, click here to start at the beginning.

One of the most widely used methods of sexing skeletal remains is by examining the skull. The skull has five different features that are observed and scored.  The five features are the:

Markers together

Each of these markers is given a numerical score from 1 to 5 relating to the level of expression, with 1 being minimal expression and 5 being maximal expression. Each feature should be scored independently, and without influence from the other identifying features. It has been generally found that female skulls are more likely to have a lower level of expression in all features, whereas male skulls are more likely to have higher levels of expression.

To observe the nuchal crest, one should view the skull from its lateral profile and feel for the smoothness (1-minimal expression) or ruggedness (5-maximal expression) of the occipital surface, and compare it with the scoring system of that feature (Figure 1).

The scoring system for expression levels in the nuchal crest.

Figure 1: The scoring system for expression levels in the nuchal crest.

To observe the mastoid process, one should view the skull from its lateral profile and compare its size and volume, not its length, with other features of the skull such as the zygomatic process of the temporal lobe and external auditory meatus. Visually compare its size with the scoring system of that feature (Figure 2). If the mastoid process only descend or projects only a small distance then it should be scored a 1 (minimal expression), where as if it is several times the width and length of the external auditory meatus, then it should be scored as a 5 (maximal expression).

Figure 2: The scoring system for the size and volume of the mastoid process.

Figure 2: The scoring system for the expression levels of the mastoid process.

To observe the supraorbital margin, one should view the skull at it’s lateral profile and place their finger against the margin of the orbit and hold the edge to determine it’s thickness. If the edge feels ‘extremely sharp’ then it would score a 1minimal expression, if it felt rounded and thick as a pencil it would score a 5maximal expression (Figure 3).

Supraorbital Margin

Figure 3: The scoring system for the expression levels of the supraorbital margin.

To observe the supraorbital ridge, one should view the skull from it’s profile and view the prominence of the supraorbital ridge. If the ridge is smooth with little or no projection, then it would score a 1minimal expression, if it is pronounced and forms a rounded ‘loaf-shaped’ ridge then it would score a 5maximal expression (Figure 4).

Supraorbital Ridge - Glabella

Figure 4: The scoring system for the expression levels of the supraorbital ridge.

To observe the mental eminence, one should view the skull front facing, and hold the mandible between the thumbs and index fingers, with the thumbs placed either side of the mental eminence. If there is little or no projection of the mental eminence, then it would score a 1minimal expression, if it is pronounced it would score a 5maximal expression (Figure 5).

Mental Eminence

Figure 5: The scoring system for the expression levels of the mental eminence.

References:

Buikstra, J.E., Ubelaker, D.H. 1994. Standards for Data Collection From Human Skeletal Remains. Fayetteville, Arkansas: Arkansas Archaeological Survey Report Number 44.

Ubelaker, D.H. 1989. Human Skeletal Remains: Excavation, Analysis, Interpretation (2nd Ed.). Washington, DC: Taraxacum.

White, T.D., Folkens, P.A. 2005. The Human Bone Manual. San Diego, CA: Academic Press. Pg 360-385.

This is the second post of the Quick Tips series on sex determination of skeletal remains. The next post in this series will focus on the use of the pelvis and parturition scars to determine biological sex. To read more Quick Tips in the meantime, click here

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Quick Tips: How To Estimate The Biological Sex Of A Human Skeleton – The Basics.

Within anthropological and archaeological sciences, ‘sex’ refers to the biological sex of an individual, based on the chromosomal difference of XX being female, and XY being male. Whereas ‘gender’ refers to the socio-cultural differences placed on the biological differences. In recent times, the words ‘gender’ and sex’ have been used incorrectly as interchangeable words within this discipline.

Therefore, it is important to remember that the word ‘gender’ refers an aspect of a person’s social identity, whereas ‘sex’ refers to the person’s biological identity.

Sexual dimorphism as seen in the human skeleton is determined by the hormones that are produced by the body. There are numerous markers on a human skeleton which can provide archaeologists and anthropologists with an estimate sex of the deceased. The areas of the skeletal remains that are studied are the:

 If the skeletal marker listed above is a link, it means that I have already covered it in an individual blog post and can be found by following the link.

The two most commonly used skeletal markers that are observed by osteologists are the skull and pelvic bone, as these show the most extreme differences.

It is generally noted that female skeleton elements are characterized by being smaller in size and lighter in construction, whereas males have larger, robust elements. Due to normal individual variation, there will always be smaller, dainty males and larger, robust females. Therefore, it is always important to observe a variety of skeletal markers to come to an accurate determination.

It should be noted that it is a lot harder to reliably deduce a juvenile/sub-adult’s sex, as many of the differences in skeletal markers only become visible after maturation, when the skeletal changes occur due to puberty. Therefore, use of DNA has been widely used to sex sub-adult skeletal remains as DNA analysis can now detect and identify X and Y chromosome-specific sequences.

References:

Buikstra, J.E., Ubelaker, D.H. 1994. Standards for Data Collection From Human Skeletal Remains. Fayetteville, Arkansas: Arkansas Archaeological Survey Report Number 44.

Ubelaker, D.H. 1989. Human Skeletal Remains: Excavation, Analysis, Interpretation (2nd Ed.). Washington, DC: Taraxacum.

White, T.D., Folkens, P.A. 2005. The Human Bone Manual. San Diego, CA: Academic Press. Pg 360-385.

This is the first of a Quick Tips series on sex determination of skeletal remains. The next post in this series will focus on the use of the skull to determine biological sex. To read more Quick Tips in the mean time, click here