In this book Parasites in Past Civilizations and Their Impact upon Health I explore how parasites affected the key cultures and societies that have shaped our world over the last 10,000 years. As director of the Cambridge Ancient Parasites Laboratory, I wanted to investigate the impact that parasites had upon the success of important past societies. With my training in medicine, archaeology and medical history I applied medical techniques to compare the health burden each experienced. Evidence for parasites brought together in the book includes studies of ancient mummies, skeletons, toilets, coprolites, hair combs, and other archaeological materials. The different kinds of parasites were detected using microscopy, analysis of proteins and ancient DNA. Calculation of Disability Adjust Life Years (DALYs) is a tool used by the World Health Organisation and scientists worldwide to compare the impact of disease in modern populations. This book is the first time DALYs have been used to compare the health effects of parasites in our ancestors.
The civilizations that appear to have suffered the most severe health consequences from parasites were that of Ancient Egypt and Nubia. There was widespread infection by malaria spread by mosquitos, leishmaniasis spread by sand flies, and schistosomiasis spread by wading in their crop irrigation systems. Malaria and schistosomiasis cause anaemia, and the reduced number of red blood cells resulted in impaired ability of labourers to do hard work. Despite this, the Egyptians managed to complete major building projects such as their pyramids, temples, and ornate tombs for kings and nobility. The widespread anaemia from parasite infection in ancient Egypt meant they would have struggled to build these monuments using their own diseased workforce alone. They could only build the ancient Egypt we see today using imported labour, such as slaves captured during military campaigns.
The next civilization that experienced a heavy burden from parasites was that of the Roman Empire. This experienced malaria and also intestinal parasites spread by poor sanitation such as roundworm, whipworm and dysentery. The marshes that existed along the Mediterranean coast following deforestation created the perfect breeding ground for the mosquitos that spread malaria in the Roman World. Dysentery was spread by overcrowding in cities, and by their use of human faeces as a fertilizer for crops.
The third most severely impacted civilizations were the populations of ancient China, Korea and Japan. They suffered with worms spread by eating raw fish and crustaceans such as Chinese liver fluke, and oriental schistosomiasis from wading in rice paddy fields. These led to chronic anaemia and sometimes cancer. The reliance of the people of ancient China, Korea and Japan upon rice, raw fish and crustaceans as food led to a distinct set of parasites and health consequences compared with other ancient civilizations.
In the Americas the most burdened civilizations were those of the west coast South America such as the Chinchorro, Maya, Moche and Inca, with many burdened with Chagas’ Disease spread by bed bugs, leishmaniasis spread by sand flies, and hookworm spread by poor sanitation. Chagas’ Disease was identified in 40-50% of mummies from the Chinchorro, Chiribaya and Inca civilizations. This parasite eventually kills those infected by causing a weak dilated heart that cannot pump blood properly, and dilated intestines that cannot digest food.
Parasites have also been spread to new regions of the world by long distance travel, and the Atlantic slave trade is a notable example. Both malaria and schistosomiasis were spread from Africa to South America and the Caribbean when slaves were forcibly transported by sea from the 1500s-1800s. Spanish, Portuguese and French slave traders have all been shown to have introduced parasites to the New World when they sold African people who were infected by malaria and schistosomiasis.
As well as investigating chronic parasite infections, the book also explores the health consequences of ectoparasites in the spread of past epidemics and pandemics. Head lice, body lice, pubic lice and fleas were found to affect the populations of ancient civilizations across the world. Fleas and body lice are known to transmit bubonic plague, so played a key role in the spread of pandemics such as the Plague of Justinian (6th century) and the Black Death (14th century). Body lice also transmit other epidemic diseases such as epidemic typhus. This highlights how the parasites on the surface of our ancestors’ bodies caused innumerable deaths in past civilizations.
This investigation would indicate that the dominant factors affecting the way in which parasites burdened ancient civilizations were their geographic location, climate, endemic insects, food preferences, approach to hygiene and cultural beliefs. These key variables determined which parasites could flourish in the civilization, how easily they spread, and the proportion of the population affected. When we consider the range of debilitating parasites that affected some of the key cultures of the past, it is a wonder how they ever managed to empire build and attain their status as a great civilization.
Author: Piers D. Mitchell