How can you tell the age of a skeleton?
If I happen to come across a skeleton, what are the giveaways that would show its sex or its age? Now I don't think he means the age of how long it's been in the ground. I think he means as in the bones. When that person died, how old were they when they died?
Emma - That's a great question. And assessing sort of sex and age at death are two of the fundamental things we do as bone specialists. I should perhaps start out by saying that if you did find a skeleton, you should leave it where it is and not touch it and let the police know just in case it's of forensic relevance. But let's assume you are volunteering on an archeological dig and you come across some skeletal remains. Well, for babies, children, and teenagers, actually it's very hard to tell what sex the individual was because a lot of the sex differences in the skeleton only really appear at puberty. But in adults there are two areas of the skeleton that we typically look at most. So the pelvis, the hip bones and the skull. The pelvis or the hips are a functional characteristic if you like, because they tend to be broader and ha ve a wider birth canal for the baby to pass through in women. So we can see sex differences there in the skull, they're mainly secondary sex characteristics. So things like males tend to have slightly heavier musculature because of higher levels of testosterone and that leaves all marks on the bones that we can then pick out. And things like the brow ridges above the eyes tend to be more developed in males as well.
Chris - What about the age question?
Emma - In terms of age at death, it's almost the other way round. So actually for babies, children and teenagers, we can get a much more precise and accurate idea of age at death. And that's based on the development of the teeth, so the formation of the teeth and also their eruption, but also on the formation of the skeleton and the bones. Whereas for adults, actually it's much harder to be really precise and accurate about how old someone was when they died because once the skeleton and the teeth have all finished forming, we have to rely basically on wear and tear on the skeleton and trying to figure out how old someone was based on this wear and tear. And obviously many factors affect that. I mean, how active you are, whether you have a good diet, how healthy you are all affect how much wear and tear your skeleton will show. So it becomes really difficult, especially for older adults.
Chris - I was very taken with that piece of research that showed that amputation in that 30,000 year old early human ancestor was reported a couple of months ago. And the fact that they were able to say this individual would've had that injury aged about 12 and they died about age 16, how would they have known that, for example, that that person survived for four years after that injury and didn't die from it?
Emma - I mean it was a really remarkable study and one way you can tell, so basically once your bone has had some kind of injury, so that could be an amputation or say you break your arm or something, the bone goes through a healing process. So we can see that if someone died about the time that an injury happened or an amputation happened, there won't be much healing. And if they survive for a while afterwards, then there will be evidence of healing and the bone smooths over that kind of thing. So particularly in that case, because in a younger individual we can be quite precise about how old they were when they died and then we know it must have taken approximately that period of time for that level of healing to occur. We can then work back and say, okay, if they were 16 when they died, they must have been say 12 when that injury or that amputation happened in this case.