I work primarily in the area of human identification in forensic science and most of that work is in the area of forensic taphonomy, which is everything that happens to somebody after they die in terms of the decomposition process. We are doing a lot of experimental work at TRACES. I have a secondary area of interest that comes from a previous career in archaeology and that is identifying remains of bird bones from archaeological sites in the Levant.
TRACES is the Taphonomic Research in Anthropology: Centre for Experimental Studies, founded 4 years ago. The research group is myself, Peter Cross, Colin Moffat, Matt Baker Judith Smith, Will Goodwin and a group of postgraduate students all working together on various aspects of decomposition. TRACES is a unique facility, the only one of its kind in UK that is dedicated to taphonomy and decomposition research and probably the only one world-wide, which has something going all the time and uses large sample sizes in testing questions about decomposition. Ideally one would work with human remains but this is not permitted in the UK.
Instead we use animal carcases, mainly pig, derived from the food chain. Researchers in the US feel that the animal work is completely irrelevant to anything human. We would argue strongly that is not the case and that what we are providing is the basic science that they have never done because we can do statistically significant sample sizes. We have never said that our work is directly applicable to calculating the time since death in humans but it does serve to eliminate lots of things that were previously thought to influence the rate of decomposition.
There were a number of studies done back in the 1980s in places like the University of Tennessee, which had the forefront of taphonomic facility for its day, where comparisons were made between the decomposition of pig carcasses and humans.
It was found that there were no significant differences in the pattern and rate of decomposition in similar body sizes. The main difference comes with the decomposition of limbs because those of pigs are short compared to those of humans. Pigs are similar to humans in that they are not covered in fur, they have similar skin thickness, they have similar digestion and diet and they are by far the best model we have.
Mostly what we are looking at is the effect of temperature and insects on decomposition which are the 2 prime movers of the process. There are equations in literature that were developed on humans, in a retrospective study in the States published in 2005, that allow you to score the state of decomposition and that will give you a figure of accumulated degree days (ADD) or in other words the average daily temperature added up over time. Once you have that ADD figure you can then go to temperature records from the time the body was found and subtract backwards the average daily temperature until you have the maximum and minimum of the range and that gives the time of the death estimate. We have done something similar for bodies in water in the UK. Probably one of the more important findings from our research is that it is really the involvement of insects that determine what type of equation you use. If insects are involved you can use the equation developed for humans in the States because body size plays a major role. If insects are not involved, wherever the body was found (e.g. indoors, buried or in water) it decays at the same rate no matter what the body size.
The main issue is temperature - the hotter things are for longer, the faster things will decompose. The biggest problem in places like the Middle East is that it is not only hot it is also very dry so frequently mummification occurs before decomposition can.
Forensic entomologists, like Colin Moffat, can. There is a lot of debate in the literature about it as well. One of my PhD students is working on heat generated by maggot masses. This is very basic level research, looking at the number of maggots that generate a particular amount of heat, in controlled circumstances. While everyone recognises that maggot masses generate their own heat, much of the developmental rate literature on insects doesn’t say how big a mass was used. So it is not 100% applicable to what happens in reality in the field when finding a corpse. Again this is research we are trying to do now to clarify some of those issues, which will be multi-stage process.
There is a fair bit that has been published.
I think a lot of the difficulty with what has been published is that it has not been done in controlled experimental ways. They are primarily coming from case studies or they have come from decomposition facilities were a sample size might be six and those six might not have been treated exactly the same and they might have been done two/three months apart. A lot of the difficulty is trying to pick out what has simply been reported and hence incorporated into common knowledge body without a lot of support for it.
Very much so, we are literally going to the literature and picking out all of the things that people have said, have an influence on the rate of decomposition and testing them one by one.
In my previous work as a forensic anthropologist in post-conflict zones and war crimes investigation situations, attempting to identify individuals who have been killed and trying to develop standards for that identification process. I am a consultant at the moment with the International Red Cross, trying to develop forms that will be used by laboratories doing this kind of work world-wide and standardising the post-mortem examination of remains.
The main issue in trying to identify people in post-conflict is finding any ante-mortem records with which to compare your findings on a body. Most post-conflict zones in the world today are in very undeveloped countries where, if records exist at all, they may be hard to obtain, may have been destroyed during the conflict, may or may not be accurate in of terms of the details that they report. The second challenge is obviously trying to get everybody doing a post-mortem examination in the same way. This is where the forms that we are developing will hopefully come in.
Birds are one of the more sensitive indicators of environmental change. Whereas mammals take quite some time to migrate, disperse and so on, birds can do this much quicker and are more environmentally sensitive because they are more niche sensitive than other types of animals. By looking at an assemblage of birds from an archaeological site dated to say 40,000 years ago, you can develop a picture of the sort of micro-climate and that gives you a better environmental reconstruction. It’s also about discovering how ancient peoples hunted and used their environment, what parts of the bird they were interested in,
what use they made of those parts and how that changes over time. I look at the skeletal remains of birds found at archaeological sites, identify the Genus and the species which can tell us a lot about the people, their environment and how they lived.
Definitely, I mean it has confirmed quite a bit of the change that was already documented in soils and lake sediments but it has also allowed us to refine it for particular sites. So I have worked mostly with those in the Jordan Valley with sites from about 800,000 years ago to the present. It goes through periods of warm and wet and comes back to encroaching desert zone which is the state we are still in today. The most recent site I have looked at is 7,000 years old, which is pre-pottery Neolithic. I lose interest in later civilisations because they start doing chickens and chickens are very boring! They do chickens to the exclusions of everything else.
Yes, there is some really interesting ones from a site that is about 800,000 years old that I did in the Northern part of the Jordan Valley, which documents the disappearance of the ‘Anhinga’ from the lake sediments. It is a diver bird that requires a particular depth of water and it highlighted the fact that the lake had diminished in depth at that time and eventually dried out completely, or that portion of it, and the geologists were able to find that in the sediments as well.
My reluctant interest in birds came about in a very bizarre kind of way. I had been working on a Neanderthal site for about four or five years and having just finished my PhD on Neanderthals I talked to the Director of the excavation about possibly being able to assume a greater role during the next series of excavations. So we had a very long conversation and he said we weren’t going to learn anything about Neanderthals from looking at the bones of the Neanderthals but from the archaeological record, what they ate and what they did and “you should do birds”, came out somewhere in this conversation and I kind of went, “WHAT!”. He went on and on and told me that I should completely switch my field and do birds. Well obviously just having done a PhD on Neanderthals and the Neanderthal anatomy I really wanted nothing to do with birds whatsoever and dismissed it completely. Some four years later whilst working at the new cave site, one his other students happened to come by and opened the conversation with “I am told that you do birds”. To which I said “No”. “Oh but the Director says you do birds. I have this fantastic site that has been submerged under Sea of Galilee for 20,000 years and there is all this fantastic preservation of bones and he tells me you do birds, so would you look at my birds please”. “Well” I said, “I could look at them but I don’t know what I could tell you” and ten years later I finally finished his 3,500 pieces of bird bone and began a career in birds in the Levant, inadvertently! It was a very steep learning curve! Since then everyone has been giving me their bird bones from their sites because nobody else does them.
That’s how that came about and I had never done birds in my life, but bones are bones!