As I mentioned in last week’s post, the age at death of a population can help us to understand and interpret its health levels. For an example, consider a group of young people that died, all together in the past. This may well be explained with an epidemic disease process that swept through a population, removing the youngest individuals who are less resistant to the disease.
As for determining age, there are several methods that are used in this study. These include dental development, calcification (e.g. the accumulation of calcium salts in bone), and the development of the skeleton. Since we are studying osteoarchaeology, the last method is the one we will look into.
There are several parts of the skeleton that can give us a near-specific age to the skeleton. These include the fusion of the skull, the epiphyses (the rounded ends to long bones), and others. Concerning the fusion of the skull: the skull of an infant consists of seven pieces of bone, with gaps between them, called skull sutures. The sutures do not join together until the child is about two years old, so that the brain can have room to grow without pressure from the skull. Any mother will know this – (Don’t touch his/her soft spot!)
The epiphyses plates, as mentioned before, are also used to determine age, as they only join to the rest of the bone at various ages – 12 to 16 for girls, 14 to 19 for boys. The great thing about epiphyses plates is that they exist in so many bones (Humerus, Radius, Ulna, Metacarpal, Phalanges, Femur, Fibular, Tibia, and Metatarsal bones) that even if some of the skeleton is lost, the age can still be found.
Telling Adult and children skeletons apart, as we have found, can be fairly straightforward, but determining ages inside adulthood can be more difficult. For this reason, there are many different methods to ageing adults, and many include recording the wear on teeth and measuring the long bones, which correspond to age. Another method is to measure the fourth rib on the ribcage. Over time, the cartilage between the end of the rib and the sternum slowly turns to bone. Measuring this increase from cartilage to bone can give an age to the overall skeleton.
Until next time,