Bones: animal or human?

By Anna Sandiford 11/04/2011 4


Although this isn’t really my area, some of my colleagues work with interesting ‘things’ that are found at crime scenes or what turn out to be crime scenes, namely bones.

A huge amount of police time can be taken up in tackling the problems of ‘stray’ bones found by members of the public or unearthed during building works.  The first question is usually, ‘are they animal or human?’  While this is being resolved, the scene needs to be made secure, someone deployed to sort it out and all the paperwork completed.  The best (and fastest) way forward is to photograph any bones with a scale and email the image to someone who knows: a forensic anthropologist such as Professor Sue Black and the team at bones@dundee.ac.uk where they provide a 7-day service with a rapid turnaround time — and an answer!  To-date, the fact that some 90% of the images they have received have been animal shows how much police time has already been saved.   Perhaps our very own Dirt Digger can help with New Zealand finds?!

For best results, all photos should be taken on a clear background with a legible scale. These photos show examples of:

what not to do….

what should be done….

One of the most frustrating problems that can arise is the casual discovery of bone, often handed in by dog walkers, gardeners or building contractors. Once the bone is identified as human the question is ‘how old is it?’ Human remains can often be seen to occupy specific places in the ground or on building sites and an archaeologist can usually give a reasonable answer as to whether the remains are of ‘forensic interest’.

However, when there is no obvious buried or concealed context the problem becomes much harder.  Sometimes, bones can be traced back to a source such as a scavenged burial and the archaeologist can be brought in again but, if not, what’s the next step?  Visual examination of whether or not the bone(s) ‘look’ old or not is unreliable and usually inaccurate and most of the scientific techniques available are unlikely to be very helpful in establishing forensic relevance.

Radiocarbon dating is one of the better ways forward, not because it can necessarily produce a precise date, but because it can sometimes determine whether the body predates or postdates the 1950s.  The reason for this is the so-called ‘bomb effect’, caused by the atomic bomb detonations, which significantly affected atmospheric radiation at that time and can be detected in organic material that incorporated the radioactive material.  Because this peak of radiation tailed off, it may be possible to calculate where on the ‘tail’ the sample sits, thus helping to give it a more accurate date (allowing, of course, for analytical error, sample type, etc.).

Radiocarbon dating is a complex process and there is a limited number of laboratories offering this service; New Zealand is, of course, the proud owner of a cutting-edge instrument.

If the bones prove to be within forensic timescales there may be dermestids present (a type of skin beetle most commonly encountered by humans as pests in stored products and carpets, although several species will also consume decaying carrion). They are therefore found with regularity by the forensic entomologist (such as Dr John Manlove at MFL in Oxford) in larger numbers where bodies have been decaying for longer as they have a distinct preference for drier feeding material.  Dermestids will feed on the fibrous tissue which remains after the bulk of the biomass of a carcass has been consumed by other insects.  They will clean all of the tissue from bones leaving only the skeleton remaining.

Dermestids can be introduced artificially in the laboratory to clean soft tissue from bones.  This has the advantage of resolving fine damage in situations where a more aggressive technique may cause damage to the bone itself. The process is a natural one which, for example, will clean the tissue from human vertebrae within a few days.  MFL has one of the two breeding colonies of dermestids in the UK (now that would be one of those ’more interesting work stories’ and it definitely sounds like something you’d see on Bones…).

All in all, discovery of a single bone can lead down roads to all sorts of interesting endings….

[written with great assistance from Dr John Manlove]


4 Responses to “Bones: animal or human?”

  • I agree Anna. ones can lead you to the most interesting stories. Archaeologists are increasingy in the UK being used by police to deal with crime investigations. Both the stratigraphy and excavation process…working out the order in which the events of the crime took place…and in the ID of bones. Are they human or animal, are they old or recent? And it is crucial that the result is correct, and that the person doing to identification of the bone is confident in their answer. This is often a very sensitive subject area.

    I have worked on a large number of human remains and burials. The difficulty as you say is in the stray bone. What species does it belong to?

    There are morphological differences between them. For us as humans, it is normally the pig that fools us. The metacarpal of pig and human are surprisingly similar. As a general rule, the cross section of bones differ between animals and humans, plus the area of articulation and a number of other identifiers.

    I reckon there is legs in this Anna.

  • Great post. I just wrote a research essay about this…well, not human vs animal bone, but estimating PMI from burials in New Zealand. It would be great if Police here used aspiring forensic archaeologists like myself for the recording and retrieval of remains and other evidence, as they do in the UK.

  • Can you help please. We recently move to a very old property (built 1880’s) and whilst diging in the garden we cam across some very old bones and wondered if they were human or animal …… We live in a rural area so don’t expect them to be huma, However it is believed that the real Jack the Ripper died and is buried in our village, so it got my imagination working. I have taken photos if you would like to see them ?

    • I suggest you contact the Centre for Human Anatomy and Identification at the University of Dundee – they deal with this sort of work; Dr Sue Black is a leading figure in this area of expertise.

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