There is all too much brutality and horror in the world. Large-scale ethnic conflicts produce massacres, with the bodies buried in hurriedly prepared mass graves. More commonly, unfortunate victims of criminal assassination are secretly relegated to lonely shallow graves halfway up some mountain.
Many years may pass before these bodies are discovered, when only the skeletons remain. Identification of the victim and the gathering of other information such as cause of death, based on the evidence of the skeletal remains alone, is the work of the forensic anthropologist.
The tasks of identification and information gathering are easiest when a complete and perfect skeleton is available for examination, but in many cases only part of the skeleton, perhaps only a few bones, is all the anthropologist has to work on. However, even here the expert may be able to draw many important conclusions.
For example, it is possible to calculate the height of the deceased by extrapolation from the length of a single leg- or arm-bone using ratio coefficients that have been continually refined since the 19th century. Also, if the remains are of a teenager or young adult it may be possible to estimate the age at death by analysing the extent of fusion of the epiphyses (growing ends of bones) to bone shafts in different bones.
The sex of a skeleton can be determined when only the skull is available for examination. Certain factors are indicative, but not conclusive, such as size (generally larger in males), the slope of the brow and the definition of brow ridges. Fortunately there are several much more definite indicators of sex.
Perhaps the best are the mastoid processes - the skull bones that reach down from behind the ear. These are relatively small in the female. If you remove the lower jaw and place a female skull on the table, the mastoid processes easily fail to reach the table surface. The mastoid processes of a male skull comfortably reach the table-top.
It is also possible to identify race accurately from an examination of the skull. For example, skulls of black people generally have wider nasal cavities, greater distance between the eyes and a more undulating brow line than skulls of white people. Structural differences are also noted between various other racial groups. One amazing technique in the toolkit of the forensic anthropologist is the ability, in collaboration with a sculptor, to recreate the full fleshy facial features of the deceased from a bony skull. This technique was first used 100 years ago by the German anatomist Wilhelm His. He measured skin thickness at key points on the faces of numerous cadavers in the morgue in Vienna.
His mission was to identify the body of Johann Sebastian Bach (1685-1750). He knew the graveyard where Bach was buried but could not identify the skeleton. Using the skin thickness measurements obtained at the morgue he constructed faces on various skulls obtained from the cemetery. One of them bore a strong resemblance to portraits of the composer.
DNA fingerprinting is a modern technique in molecular biology that is of great use to the forensic anthropologist. Its value rests on the fact that, although our genetic blueprint, DNA, is unique to every one of us as individuals, there are resemblances between parts of the DNA sequence and sequences in the DNA of our close relatives. A careful comparison of DNA taken from a skeleton and compared with DNA samples obtained from suspected relatives (living or dead) may therefore positively identify the deceased.
The technique of DNA fingerprinting was developed by a British scientist, Alec Jeffreys, in 1984. Its applications in forensic science were quickly obvious. In 1983 the body of a raped and murdered girl was found in Leicester. In 1986 the body of another girl was found in the same place in the same circumstances. Police believed that the same man committed both crimes. A suspect confessed to the second murder.
The police asked Jeffreys to carry out DNA fingerprinting. Samples of the rapist's semen had been collected from both victims but the semen's DNA fingerprints did not match the suspect who confessed, and who was therefore exonerated. A massive manhunt ensued. Eventually, a man was arrested following some overheard remarks he made in a pub. DNA fingerprints of his semen matched the samples collected from the unfortunate girls.
One interesting and very useful application of genetic fingerprinting is the identification of children who "disappeared" (i.e. who were abducted by the authorities) in Argentina during the military rule (1976-1983) and their reunification with their relatives.
Many of the children were too young at the time of abduction to have any memory of the event. A genetic data bank of blood samples from relatives of children who went missing has been established and is used to check the identities of people, now adults, suspected or known to have been abducted as children under the military regime.
Another interesting application of forensic genetic fingerprinting concerns Josef Mengele, the Nazi war criminal, who is said to have escaped to South America after the second World War, where he lived in hiding until his (presumed) death. Some years ago a claim was made that the corpse of Mengele had been found.
Alec Jeffrey extracted DNA from bones of the supposed skeleton of Mengele. A DNA fingerprint prepared from this material was compared with a fingerprint made from DNA donated by Mengele's still-living son. The comparison positively identified the remains as those of the "Angel of Death".
William Reville is a Senior Lecturer in Biochemistry and Director of Microscopy at UCC