How do archaeologists determine the sex of a skeleton?

At first glance, a femur or a jawbone doesn't tell much . But under the expert eye of archaeologists , these bone remains can reveal such fundamental information as the biological sex of the person to whom they belonged. However, it's a task that is far from exact and requires a combination of science, context, and caution.

"We're seeing differences in shape and size between the sexes," biological anthropologist Sean Tallman of Boston University recently explained to Live Science . His caveat, however, is clear: "No method is 100% accurate." The statement nicely sums up the dilemma many researchers face when trying to assign a sex to remains that, in many cases, have spent centuries underground.

Most measurement-based techniques assume that men are larger and taller than women (by about 15%), and sex predictions from measurements are only 80% to 90% accurate . However, if the skeleton's pelvis is well preserved, simply observing certain features is often a more accurate method than relying on leg bone measurements.

Indeed, one of the best-known methods involves studying the pelvis, one of the body parts with the greatest differences between the sexes. The technique developed by anthropologist T.W. Phenice in 1969 remains a benchmark: it is based on observing specific characteristics of the pubic bone that tend to vary between men and women. When skeletal conditions are favorable, this technique can offer a high level of precision.

Male skulls tend to be more robust, with squarer jaws. Female skulls are usually more graceful.

The skull also provides valuable clues. Male skulls tend to be more robust, with more prominent brow ridges and squarer jaws, while female skulls are often more graceful. However, these differences can be subtle and are subject to individual variation.

Furthermore, in recent years, genetic analysis has transformed the field . Researchers like Hila May of Tel Aviv University use DNA markers to identify biological sex with a reliability approaching 99%. One of the most recent discoveries involves the use of a gene linked to tooth enamel, which allows for results even when other tests fail. However, the state of preservation of the DNA is crucial: it is often not possible to extract it from very old skeletons.

As anthropologist Virginia Estabrook told the same outlet, around 1.7% of the population is some form of intersex—just under one in 50 people. She emphasizes this because understanding who a person was can be hampered, and interpretations are sometimes misguided. To give a few examples: in Pompeii, for example, DNA analysis revealed that a set of skeletons supposed to belong to a mother and her biological son were actually a man and an unrelated boy, and in 2019, a Viking burial filled with weapons was found to be chromosomally female rather than male.

At first glance, a femur or a jawbone doesn't tell much . But under the expert eye of archaeologists , these bone remains can reveal such fundamental information as the biological sex of the person to whom they belonged. However, it's a task that is far from exact and requires a combination of science, context, and caution.