A female skull in profile
Side view of a female skull

Estimating sex from the skull

The skull can also be used to accurately determine sex, with general estimates indicating an approximately 85% success rate in estimating sex based on the skull alone. As with the pelvis, the accuracy of sex estimation is dependent on the state of preservation, as well as the degree and range of sexual dimorphism within the skeletal sample. Overall, the male skull tends to be larger, have a lower, sloping forehead, larger muscle attachment sites and smaller, squarer eye sockets when compared to females. There is overlap between the sexes and it is not uncommon for individuals to exhibit a mixture of ‘masculine’ and ‘feminine’ features. The individual traits to record are as follows:

Orbit

In females, the margins of the orbits are sharper, the shape is more rounded and the socket larger relative to the overall size of the face than in males. In males, the margins are more rounded and the shape is more square.

Glabella and supra-orbital ridge

The supra-orbital ridges, sometimes known as the brow ridges and the glabella, or approximate centre of the forehead between the supra-orbital ridges, are more pronounced and rounded in males and less marked in females.

A female skull A female skull displaying smooth, gracile supra-orbital ridges and glabella.

A male skull A male cranium displaying pronounced supra-orbital ridges and glabella.

Forehead

The forehead tends to be more upright in females, while it is often more sloping in males.

A male and female skull facing each other in opposition, highlighting the differences in the glabella and supra-orbital ridges A male (left) and female (right) skull in profile displaying differences in the glabella and supra-orbital ridge (green lines) and forehead (blue lines).

Temporal Bone

The mastoid process is larger in males than in females. In males, there is often a ridge above the mastoid process from the posterior zygomatic arch.

Side view of a female skull focusing in on the temporal bone Female temporal bone with the mastoid process highlighted in yellow.

Side view of a male skull focusing in on the temporal bone Male temporal bone with the mastoid process and ridge highlighted in red.

Occipital Bone

The nuchal crest located on the occipital bone at the back of the head is more pronounced in males than in females.

Back of a female skull Female occipital bone with a smooth, gracile nuchal crest.

Back of a male skull Male occipital bone with a pronounced, rugose nuchal crest.

Mandible

The mental eminence (chin) is often larger and squarer in males and pointed and smaller in females. The mandibular ramus (vertical part of the jaw) is also more upright in males, while it tends to be smaller and more sloping in females. In males, there is usually a greater degree of muscle marking in the gonial region (angle between the horizontal and upright parts) and what’s referred to as gonial flaring.

Male mandible Male mandible

Female mandible Female mandible

Male and female mandibulae Female and male mandibulae

Here is a table describing several sexually dimorphic features of the skull.

Skull Sex

Below are videos displaying male and female mandibles. See if you can spot all of the sexually dimorphic features.

In addition, make use of the 3D models demonstrating features on the skull used to estimate sex. They can be found in the ‘SEE ALSO’ section below this article.

Female Mandible

This is an additional video, hosted on YouTube.

Male Mandible

This is an additional video, hosted on YouTube.

NB

Please note that the five criteria for sex determination (i.e. ‘Male’, ‘Probable Male’, ‘Indeterminate’, ‘Probable Female’ and ‘Female’) are not used in all contexts. For example, the ICRC promote using only three categories (‘Probable Male’, ‘Intermediate’, and ‘Probable Female’’ until identification is made.

Now that you’ve learned how to estimate sex from adult skeletal remains, you can move on to the next step, which will instruct you how to assess age-at-death in non-adult or infant and juvenile remains.

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This article is from the free online course:

Forensic Archaeology and Anthropology

Durham University