Forensic Anthropology: How Old is Too Old?

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I recently posted an overview of forensic anthropology.  In the comments, my blogging friend G'Eagle asked how old remains could be before they were too old.

One the tremendous things about forensic anthropology is that it lasts as long as the bones do.  Bones do decompose, and they subject to weathering and damage after death, but they do last a very long time, and as long as there is bone material left, there is some how for forensic anthropologists to be able to recover useful information.

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Biorachaeologists specialize in the excavation and analysis of historic or prehistoric human remains.  They use many of the same techniques that forensic anthropologists use to get at much the same information.  They use these techniques to examine radiographic images of Egyptian mummies, and have been able to recreate the likely scenario of murder of the famous Oetzi the iceman from 5,300 years ago. I have personally determined the age, sex, and some health history of individuals whose remains were 3,000 years old.  I have also been able to say something about peri-mortem wounds on skulls that age.

Forensic anthropologists work in the context of criminal investigations, so they're not worrying about remains that are that old, but this does suggest that, however old the bones are, the age of the bones is not necessarily a concern for forensic anthropology.

That said, completeness and preservation are important.  The more skeletal material is present to be analyzed, the greater the likelihood that an anthropologist will be able to recover useful information.  The better preserved the bones, the more accurate and precise that information will be.  Time itself may not be an enemy, but time does increase the odds of remains being subject to other destructive forces:

• Water
• Bacteria
• Crushing
• Cracking
• Sun
• Fire
• Gnawing by rodest
• Etching by roots
• and so many more

A dry environment that shelters the remains will preserve bones for a considerable time.  As soft tissue mummifies (which can happen naturally) this can help provide a leathery, protective casing for the bones that further shields them from damage.  The more moisture, animals, and open environment remains are exposed to, the more likely that bones will be scattered, damaged, or completely destroyed.

Since forensic anthropology usually works hand-in-hand with law enforcement, it is very often the context of the case which determines how old is too old.  One case I worked, we had a skull and some scattered other remains, and it was enough to show consistency with presumed identity of the victim and to piece together perimortem damage on a serial killer victim from twenty years previous.  

A couple other cases, we had remains that were less than a year old.  One victim was in a dry environment with little stress, and we were able to recover almost every bone and they were all in good shape.  Another victim was in a wet, highly organic environment, and most of the skeletal material was already badly damaged.  However, because of the legal context of the two cases, all they really needed from us was confirmation that the remains could be of a certain basic demographic, and we were able to provide law enforcement that information.

Any other questions?

.Nevets.