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Forensic Anthropology: One Way to Determine Sex From the Pelvis

Back of a skeleton's head and neck

Even though I am a Medical Anthropologist, I have taken graduate-level courses in Forensic Anthropology as well. If my love for Medical Anthropology is at #1, then Forensic Anthropology is at #2! Eventually, I will be offering online classes in Forensic Anthropology through my website and the Udemy platform (once I have purchased all the expensive supplies that I need). In the meantime, I’d like to share some techniques with you through my blog. 

In this blog post, I’ll show you an easy way to determine the sex of a skeleton just by looking at the pelvis. I’ll assume you know nothing about human anatomy or osteology (the study of the skeleton). 

So, let’s start with the pelvis. What is it? The pelvis is a set of bones that connects your trunk to your legs. The pelvis is circled in red in the image below.

How to determine sex from the pelvis. Image of a human skeleton with the pelvis circled in red.

The pelvis is made up of 4 bones: the right innominate, the left innominate, the sacrum, and the coccyx. 

Here are images of the right innominate and the left innominate. They are also known as the hip bones.

How to determine sex from the pelvis. Image of a right hip bone, called the innominate bone.
How to determine sex from the pelvis. Image of a left hip bone, called an innominate bone.

Here’s an image of the sacrum, which is the lower part of your spine. The lower vertebrae (segments of your spine) are fused together to make the sacrum.

Image of a human sacrum bone.

Here’s an image of the coccyx. This is also known as your tailbone. 

Image of a human coccyx bone.

And, here is an image of all the bones in the pelvis connected together. When bones are connected together, they are said to be articulated. You can see the right and left innominate bones, the sacrum, and the coccyx.

Image of a human pelvis with the bones labeled in red.

Now you know what the pelvis is! The next step is figuring out whether a pelvis belongs to a male or a female. There are a few different ways to do this, but I’m just going to explain one method.

In the images below, look at the angles made by the innominate bones touching each other, marked in red. This is called the subpubic angle. In the image of the first pelvis, the subpubic angle is wide. In the image of the second pelvis, the subpubic angle is narrow. 

Image of a human pelvis with the subpubic angle marked in red.
Image of a human pelvis with the subpubic angle marked in red.

Why do we care about the subpubic angle? Well, because in females, the subpubic angle is wide, and in males the subpubic angle is narrow. So, pelvis #1 is female and pelvis #2 is male! In reality, you would make the final determination of sex based on several characteristics, not just one, but that’s beyond the scope of this blog post.

Image of a female human pelvis.
Image of a male human pelvis.

I hope you enjoyed learning one way to determine the sex of a skeleton based on the pelvis! 

Want to learn more about Forensic Anthropology? Check out the website of the Smithsonian National Museum of Natural History!

Thanks for reading!