Near the Chillian Atacama desert, between 75,000- 2500 years ago, the state of public health was a grim affair. The native people – the Chinchorro, could expect to live on average just 25 years, lost a quarter of thier children before their first year of life and curiously, over one third of people suffered from acute infections of the legs which degraded their very bones. The women it seemed suffered in particularly horrific ways. For those of child bearing age, 20% had bones so brittle and porous that the simple weight of their bodies caused their frames to crumble and collapse within them, fatally snapping their spines.
The Chinchorro were a special people. They lived in a world inhabited by the physical presence of both the living and the deceased. They were among the first known groups to practice mummification of their loved ones – ahead of the Egyptians by many thousands of years. The dead were deliberately preserved, wrapped in clay, conscientiously and creatively decorated and buried in chambers located in the parched sands of the desert which lay near their coastal home. The dryness of the desert benefited the preservation process– creating the opportunity for scientists to later exhume these remains and study them in depth. But what caused the apparent poor health of these people, which resulted in such devastating effects on mortality and life expectancy?
The answer, or part of it, appears to lie in poo. Its examination can reveal inner secrets of the body and ascertain causes of pathology and is a standard practice in modern healthcare systems. Yet surprisingly, ancient, desiccated faeces – known as ‘coprolites’, also provide an essential window into the lives of civilisations and people long lost. These artefacts of existence are considered trace fossils – they don’t document form or function of bones and bodies, but rather, they tell poignant stories of diet and behaviour. Incredibly, despite lying in a shrivelled slumber for an untold age, once rehydrated, and in the right hands, molecules and objects held within coprolites can provide a startling image of archaic worlds. Protein analysis of samples for instance, can describe cannibalistic tendencies. Examination of vegetation and pollen matter describes not only what people were eating, but also the ancient landscape in which they lived, from the floral composition to indications of climate and climate change.
However, one particular component of these miniature mines of archeological treasure can provide more clues than perhaps anything else:
Parasites.
All organisms have parasites – it is the natural norm rather than the exception. A parasite can be broadly considered as any living thing which lives off or at the expense of another (the host) who gains seemingly little from the association but who potentially stands to lose something as a result of the interaction. The degree to which this loss is detrimental to the host is variable, ranging from negligible to ultimately, loss of the hosts potential to reproduce, through infection, disease and ultimately, death.
The human body provides an eye-watering number of niches to which approximately 400 species of bacteria, viruses, fungi, single celled protozoan organisms, and multicellular animals such as parasitic worms have evolved to become adapted and specialised to exploiting for resources. The Human gut is just one of these, however when considering the knowledge sequestered in coprolites, our understanding of the digestive system’s parasites becomes of paramount importance.
Examination of human coprolites, collected from ancient latrines and defecation spots, as well as obtained from mummies and preserved corpses have thus far revealed a picture of the parasitic fauna of races and ethnic groups from around the globe, across a considerable cross section of human evolutionary history. Species such as the human hookworm (Ancyclostoma duodenale) which require suitably warm temperatures to survive and develop, for instance, demonstrate that, because thier eggs have been found preserved in coprolites from South America, the first peoples to travel from Eurasia to these areas must have done so along the warmer coast line, not as was opreviously thought, across the cold Beringa straight of North America. The parasite, which requires external development in the environment before it infects a human host, simply could not have maintained its lifecycle and survived at the temperatures the people would have experienced had they taken this migration route. Thus, we can peice together fragments of our own species' history based on the assumptions that can be made when coprolites throw up thier parasitic secrets and when we know a little about the natural history of the species concearned.
As for the Chinchorro, it would appear that a parasitic tapeworm usually found in sealions – Diphylobothrium pacificum, which can grow up to 16 ft long and is obtained from eating infected fish, may have been a cause of their bone shattering affliction. The people relied heavily on a fish based diet – approximately 30% of the stomach content of the mummies contains fish remains. The parasite is so efficient at the uptake of nutrients from the hosts body that deformed red blood cells can form, generating a type of anaemia which can result in the porous bone disease found in around 25% of the mummies examined. Coprolites provide the evidence that this may have been the cause – the characteristic eggs of the worm have been found in a number of Chinchorro samples, indicating that the people were infected by this parasite – obtained as a result of their dependence on coastal fish for food.
Not only can we learn about our past, from the parasites preserved in coprolites, but we can also learn about theirs and the evolutionary history of interactions that exist between us. This understanding not only helps to fill in some of the many gaps that exist in our knowledge of our own social and cultural inheritance, but could be of fundamental importance for the control of modern, re-emerging and newly emerging infectious disease. Of course there are problems associated with coprolite analysis - contamination with fungi, bacteria, degredation of DNA making molecular analysis difficult etc, but these aside, it is an interesting thought; what will people of the future find out about our lives, behaviour and culture, should they look to uncover the preserved organisms in our faeces? What might your 'poo', say about YOU?
