Science Sunday: Skeletal Remains

By: Meradeth Houston on 11:30 AM

Welcome to Science Sundays! Today I thought I'd launch into a topic I spent a while going over with my students this past week: how to tell the sex of an individual from the skeleton. More specifically I thought I'd hit the high points of the pelvis, because really there are textbooks worth of information on this subject :)

This is the view from the back (butt side).

Okay, starting off with the pelvis itself: it's official name is the os coxae and it's made up of two halves, connected in the back by the sacrum (the lower fused part of the spinal column). It happens to be the best spot to tell what sex an individual was due to all kinds of differences between males and females. Do keep in mind that all of these traits exhibit a range of variation because all humans are different, so there may be some traits that overlap in their distribution between males and females.

(Confusing you yet? Here's an example: males are generally taller than females, so a tall skeleton would be thought to be more likely male than female, but of course there are tall females too, so it could also be a female. Same thing applies here--the range of variation may be leaning toward one sex, but sometimes the variability falls into the grey area in the middle.)

highlighted area is the notch.

Anyhow, say you've got a character stumbling across a skeleton in the woods. The best way they're going to be able to tell if the person was male or female would be by looking at the greater sciatic notch. This is going to be right below the part of the pelvis where the top of the femur (upper leg bone) fits in. It'll be a giant, well, notch :) Females generally tend to have a more U shaped notch, whereas males tend to have a more V shaped notch. This is kind of the quick and dirty way to get at the sex.

The 1 is more female, the 5 more male.

Now, I'd never recommend touching remains that are found unless there's a real reason to. Why? Well there's all kinds of forensic evidence that can be accidentally messed with, let alone leaving behind some of your own, so it's better to Not Touch. Buuuut, if your character decides they have to for some reason there are a few other things that can be looked for:

Prearicular sulcus region.

>The prearicular sulcus. This is going to be on the top side of the sciatic notch, close to the auricular surface (the rough patch if the sacrum has become disconnected, or next to the sacrum is still attached, right by that). If there's a small, long divot (sulcus) there, then it's more likely to be female.

>There are three traits that are found on the pubis bone of the pelvis (each half of the pelvis is actually made up if three, fused bones [in adulthood] that are known at the ilium, ischium, and pubis). The pubic bone is the one that comes together in the front, belly-side of the body in the pubic area (hence the name!). These traits are kind of hard to describe without actually looking at a bone but if you're curious, these are things that can also be analyzed:

Ventral Arc: A is female, B is male.

Subpubic concavity: C is female, D is male.

Ischiopubic ramus ridge: B is female, F is male.

-Ventral Arc.
-Subpubic Concavity.
-Ischiopubic Ramus Ridge.

Yay! So, that's the best way to tell what sex an individual was in life. Do keep in mind this doesn't mean their gender :) (I always kind of wonder if this gets any more particularly confusing in areas with large LBQT communities where the sex an individual is born with can be different from their gender--the underlying bones don't change without obvious modification...something random I think about, which is probably an insight into my mind that you didn't want to know!)

Questions?