Estimating Age-at-Death in Adults

In this section, we’re going to focus on estimating the age-at-death of adult skeletal remains. Now this is a little bit trickier than it is with non-adult skeletal remains because the changes that we’re looking at are primarily degenerative, and so they can vary between individuals. And also the changes are much more subtle than they are with non-adults. And this is partly because it’s an interplay between an individual’s lifestyle, their environment, and their genetics. And that creates differences between individuals in terms of the rate at which they age as well. So there is a much looser correlation between the biological aspects of the skeleton and chronological age than there is with the non adult skeletons.

There are a number of later fusing epiphyses that don’t fuse until the late teens to early 20s on the pelvis and these can be useful for age estimation. So if we look here, on the ischial tuberosity you can see that it’s got an unfused surface texture, it’s nice and wavy. And here is the epiphysis, you can see that it’s very delicate and fragile, and this will fragment quite easily on the ground. So eventually, this will gradually fuse on to here like this. If we look at this pelvis here you can see that this is fused on. And you can see that the fusion line is clearly visible.

If we look at the iliac crest here, you can see that is still unfused. So even though the ischial tuberosity is fused on, the iliac crest still has that wavy surface. And that will be a separate epiphysis in the same way that the ischial tuberosity was. If we look at this pelvis here, you can see that the iliac crest is starting to fuse on, but the fusion line again is clearly visible. So that shows us that fusion has been fairly recent. For adult age estimation, I’m going to talk about two features of the pelvis, the pubic symphysis here, and the auricular surface. The auricular surface tends to preserve a little bit more frequently than the pubic symphysis.

And that’s because if we imagine a body lying on its back in the ground, the pubic symphysis is quite exposed. This is very easily damaged by spades or equipment used to excavate the individual. You can see that it’s also a very fragile bit of the body. The method that’s used most frequently to estimate age from the pubic symphysis is the Suchey-Brooks method. And part of the reason that this is popular is because they produced a set of casts for male and female pubic symphyses. And their method is a six phase system. So we’ve got the younger phase here, this is phase one, two, three, four, five, six.

And what they’re showing here are the earlier and later stages of each of those phases. So, the pubic symphysis then undergoes fairly regular morphological changes with age. In phase one, you can see that the surface is very billowed. And that’s essentially because it’s an unfused epiphysis. When you get to phase two, you start to see these nodules or ossifications appear at the top and bottom of the pubic symphyseal face. And you get what’s called ventral rampart formation, so a bony bridge on the ventral aspect of the pubic symphysis. Then you have a complete rim that’s formed around the pubic symphysis surface, and you might still get some ridges going across.

These ridges gradually disappear, and you have a flattened surface with a defined rim, which then will gradually degenerate and deteriorate. So you’ll start to get degeneration of the rim and porosity on the pubic symphyseal surface. The reason that there are different casts for males and females is that there are differences between the two because of childbirth. What I find is that the female pubic symphyses are much less regular in terms of the age changes than the male, and they’re much more variable than the male. They can also be difficult to use the age estimation because they’re quite small, and the changes are harder to spot generally. There are a couple of limitations with the method.

Some people have argued that once the ventral rampart has formed, between the ages of about 30 to 40 years, the method is less reliable. The key limitation, though, for archaeological and forensic cases is that it doesn’t survive very frequently. And this is because it’s quite a fragile bit of bone. And when the skeleton is lying on the back, it’s quite exposed. So quite often, it’s knocked off completely or it’s very abraded, and it’s difficult to use. The features on the Brooks and Suchey casts don’t show up very well on film. So we’ve got some archaeological examples to go through with you here.

Starting with the first one here, you can see that it’s got a very billowed appearance, and this is youthful and this would put it in stage one. Ignore the abrasion here at the top and if you just focus on these billows, it has essentially an unfused epiphysis appearance. And that’s what it is. If we look at stage two here, you can see this bony nodule here at the top, you can see that there’s no rim around it. And this would fit into stage two of the Brooks and Suchey system. And you can see the slight ridging across as well. If we have a look at this third one here, you can see that the ventral rampart has actually completely formed.

Quite often you’ll end up with a hiatus in the rampart here, but it has formed and there are some slight ridges going across it that you can just about spot. And this would be either in stage three or stage four. This example here, you can see that the rim is complete, there’s very little evidence of ridges on the surface, and this would probably be in stage five. If we look at this final one, you can see that the rim has started to degenerate, and that the surface is showing some porosity as well. And this would put it in stage six of the Brooks and Suchey system.

Similar to the pubic symphysis, the morphological changes to the auricular surface relate to alterations in the surface texture and appearance, together with changes at the margins of the joint. In the 1980s, Lovejoy and colleagues created an eight phase system to characterize the age related changes. We’ve got some archaeological examples here to show you some of the key changes that you’ll see with age. Here, we’ve got a very youthful looking auricular surface. And you can see that the surface texture is very fine grained, and the method describes it as billowed. This can be confusing because it’s not billowed in the same sense as the pubic symphysis is. The billows are much more subtle.

You’ll also see some striae or what’s referred to in the method as transverse organisation. With increasing age, the billowing will disappear, and the surface becomes slightly coarser grained, so if you think about the coarser grained sand paper. The striae and billowing will disappear, and you’ll have a more uniform surface texture, a bit like you’re seeing here. Gradually, the surface texture will start to get some microporosity, so little holes in it. And it will also start to get some very dense patches. So if we look at this example here, you’re seeing lots of microporosity and also some slightly larger holes referred to as macroporosity. And you’ve got dense areas appearing in the surface texture.

There’s no evidence of any transverse organisation and the surface texture is quite irregular in structure. In the final example, this is our very oldest individual here, you see that the surface texture is extremely dense, very irregular, and you might also see some changes to the apex of the joint. The auricular surface method is not as popular amongst many osteologists as the pubic symphysis method. And this is because the morphological changes between the different stages are much more subtle than they are with the pubic symphysis, and they’re much more difficult to interpret. As a result, there’s a greater likelihood of inter-observer variability. The advantage of the auricular surface method is that it preserves much more frequently than the pubic symphysis.

Another advantage is that it doesn’t display such marked sexual dimorphism as the pubic symphysis, so the changes are broadly consistent between males and females. While the pubic symphysis might be more accurate up until about 30 or 40 years of age, after the formation of the ventral rampart, the auricular surface can then be better for age estimation purposes. Because the densification of the auricular surface continues to increase with increasing age, so it becomes easier to identify older individuals. A method of age estimation that’s used in forensic cases is the sternal end of the fourth rib. If you don’t have the fourth rib it’s possible to substitute the third or the fifth rib.

This method is not used very frequently in archaeological cases, because the ribs tend to be poorly preserved and very fragmentary. Here is some archaeological examples to show you. Starting off with this younger individual. Here, you can see there’s just a slight indentation and the margins of the joint are nice and clear. Here in this individual, you can see that there is a pit forming. And you can see that the walls of the rib around the edges of the pit are slightly irregular. When we look at this older individual here, you can see that there’s a very deep pit, and you can see that the joint cartilage has begun to ossify and the margins are very irregular.

For young adult skeletons, the sternal end of the clavicle can be a useful indicator of age-at-death. You can see here that this is an unfused surface. And this individual is likely to be in their early 20s, certainly less than 25 years of age. This individual has a partially fused sternal end of the clavicle. And this individual, you can see that it’s completely fused. When you see partial fusion like this, it usually indicates that the individual is 25 years or less. But certainly by 30 years of age, fusion is complete in almost all individuals. So there were the different techniques for estimating the age-at-death of adult skeletons.

As you’ve seen, some of the changes are very subtle and can be difficult to interpret. And you do get a lot of variability in terms of the expression of these degenerative changes. As a result of this, we use these quite broad age categories for adults. In the next section we’re going to examine the different techniques for establishing stature from a human skeleton.