Bodies of Evidence

Article excerpt

New investigative techniques based on genetics and immunology are shedding light on everything from the spread of disease to the origins of the human race, as Hilary Bower reports

Mummies do not welcome internal investigations. Their innards are rigid and the scientist wielding the endoscope -- a long fibre-optic tube with a tiny video camera and scissors at its tip -- has to be skilled to coax it deep enough into tile ancient body to allow a snip of tissue to be taken. But coax they do. These Egyptologists from Manchester University have perfected this invasive technique of retrieving precious samples of humans long dead, but alive with invisible information.

Dr Rosalie David and her team at Manchester University Museum hope to amass a collection of about 8,000 endoscopic tissue samples -- some more than 5,000 years old -- from mummies around the world; a unique resource to practise new investigative techniques that are transforming our knowledge of tile past.

Based largely on genetics and immunology, these techniques promise to shed new light on everything from the spread of infectious disease and the development of agriculture to tile origins and migrations of the human race itself.

David and her team are currently investigating DNA evidence of parasitical diseases such as bilharzia in the hope that by tracking a disease's mutation over the centuries, tile potential for new treatments may be revealed.

"In ancient Egypt you get idealised artists' representations of the people in the temples and monuments because that is how people wanted to go on into the next life," says David. "But the reality of what their lives were like is in the body."

"In future we will be able to use genetic investigation to look at family relationships between mummies, to see how families were arranged and how movements of population or foreign migration occurred at different times, either peacefully or by invasion."

There is also the potential for cross-cultural studies. "There are pre-Hispanic mummies in the Canary Islands and in South America," adds David. "There are bog and frozen bodies, and naturally desiccated bodies in Mongolia which were found buried with tartan clothing and hats like the witches hats of Europe. Instead of making educated guesses from literature, we'll be able to trace population movement quite widely."

According to Professor Robert Foley, head of the Human Evolutionary Biology Research Group in Cambridge, genetics has revolutionised the study of human evolution and history.

"It is now possible to infer detailed aspects of human history from the distribution and frequency of genes found around the world today," says Foley. "Genes are like tracers, little markers on populations, and what we are trying to understand is the behaviour, the demographics and so on that have produced the patterns they make in the genome."

The key process to illuminate these patterns is polymerase chain reaction, or PCR, a laboratory test that works by amplifying tiny samples of DNA until there is enough available to read the genetic code and compare it with other samples. While medical geneticists search for gene mutations that link disease and affected individuals, the Holy Grail for anthropologists, geographers and others is "genetic variation" -- simply the number of differences between a particular stretch of one person's DNA and another person's DNA.

Since mutations occur at a predictable rate, it is now possible to estimate how far groups of people are from a common ancestor by counting such differences. The more similar two individuals are, the more closely they are related. The more different they are, the further back in time they shared an ancestor.

Tracing genetic variation is proving a valuable tool in some of anthropology's most fundamental questions. It has, for example, almost settled the long-running and highly-charged debate over whether modern humans evolved as a species in Africa, then migrated out to replace other early hominids such as Homo erectus, or whether, in fact, we evolved from such early hominids. …