Nubia, irrigation and parasitic worms, a tale told by a Mummy
// June 8th, 2011 // Recent Research
A few months ago I wrote about Ancient Nubians and their antibiotic beer, delivering a dose of tetracycline in every brew.
Now bioarcheologist George Armelagos has co-authored a study showing that early irrigation channels changed how humans were affected by parasites.
I’ll describe the research at the end, but first – a story! Make yourself a cup of tea and come back to read it.
Nubia, 500ADSince he’d taken his first wobbly steps on Nubian soil, Alara had been pulling his then insubstantial weight on the family farm. He’d pull up weeds with grubby fingers under the watchful eye of his older cousins by day. Lunch was often a paltry loaf of flat bread to share between the lot of them, supplemented with whatever local edible plant was in season, eaten hastily and followed by a brief break in which he built dirt pyramids with other children.
Now 30, Alara remembered his childhood as carefree and unplanned. His memories swam together like waves billowed out from boats on the Nile. Only small moments stood out with any clarity. A snarling dog snapping at his leg. The taste of bread warmed by the sun, seasoned with hunger. Buzzing with disbelief at the stories told by his cousins of things adult and forbidden.
A life in the sun had baked him hard and capable, and he still worked on the same farm he had as a toddler. His extended family shared the plot of land, shared the work, shared the harvest, shared the income. Shared the good years and the bad. He was a cotton farmer through and through, born and raised to the plough.
A friendly slap on the should shook Alara out of his reverie. “Wake up, brother, you are asleep on your feet! It’s time for lunch and then I need to walk to the river and check the channels. The water is not flowing as it should. Will you go with me?”
“Lunch already, Arty? I didn’t notice the sun was so high. Of course I’ll come with you.”
The midday meal of onion and lentils served with flat bread for eating with was waiting hot on the table. They ate quickly and had a weak cup of tea before walking to the Nile.
They could hear the river well before they could see it. The sound of saqiya irrigation was like music that infiltrated the whole valley, though they were so used to it they barely heard it. As they approached their saqiya, they called out a greeting to Nala who was driving the cow.
“Nala! We have brought food for you.”
“Thank you uncle,” she called back. “I’ll come down to eat.”The saqiya was the heart of the farm, pumping the water of life from the river to the fields where it was needed. Made of wood, it consisted of cogs and a large open-spoked wheel. The cow, encouraged by young Nala, moved a wooden arm around, turning the wheels and cogs to move a pulley.
That pulley was studded with jars which dipped down into the water and lifted up to the farm’s main channel. Each jar then deposited its precious load which ran to the farm and branched out into smaller channels, delivering water for the cotton.
Alara inspected the cow and saqiya while Nala ate lunch. Despite a slightly thirsty cow, everything seemed to be working fine. The problem must lie in one of the channels.
Walking along the main channel, he stopped now and then to check the water level. Sometimes silt and aquatic plants collected at the bottom, blocking the flow of water. When he and Arty came to the first branch in the channel, they separated to cover more ground. Following his channel through several other branches, Alara found one that was a problem.
The side of the channel must have collapsed recently. Mud clogged the small stream, causing water to dam up behind it and overflow. Alara reached in and started to pull up clumps of the stuff. The water became turbulent and muddy, and he noticed more than a few of the fresh-water snails that liked to live in the slowly flowing channels. As he cleared it, the water began to run clean again and move into the farm. He spent the rest of the afternoon checking other channels, clearing several that were silting badly.
Though he didn’t know it, those snails were responsible for the troubling, itchy spots many adults had on their arms and feet. Well, it wasn’t the snails exactly, it was the tiny worms inside them.
Several species of trematode of the genus Schistosoma could infect humans. These tiny parasitic worms hatched in water and quickly found snails to infect, burrowing into their large feet. They moved through the life stages of miracidia and sporocyst inside that host, emerging as free swimming cercariae which needed a mammal host to continue to the next stages.
In contact with humans, or for some species other animals, they penetrated the skin and lost their tails, moving through the circulation as schistosomulae. In the liver they would mature into adults, pair, and migrate so the eggs they produced would be shed in stool. Those eggs would make their way to water to repeat the cycle.
Two weeks later, Alara woke in the night with a pain in his stomach which sent him running to the toilet area. By morning he was exhausted and feverish. Though the disease didn’t kill him, researchers would later find evidence of the parasitic worms in his mumified remains.
Schistosomiasis, the chronic disease caused by these worms, is thought “the most important water-based disease from a global public-health perspective” in modern populations. It infects an estimated 200 million people per year. It has a low mortality rate, but causes development problems in children and damages internal organs.
Modern irrigation systems, particularly slow moving ones, boost the disease by providing habitats to the snails. But what about ancient populations?
To find out, Armelagos, Hibbs, Secor and Van Gerven studied dessicated remains (aka mummies) from two Nubian populations. Wadi Halfa (N = 46) lived in 500AD when the Nile was lower, and used saqiya irrigation on their crops. Kulubnarti (N = 191) lived 300 years later, during a time when Nile flooding was good and irrigation was less critical. They hypothesised the Wadi Halfa population would have more Schistosoma mansoni, and it would be more prevalent in children and men due to differential water contact.
One out of three ain’t bad. Indeed, Wadi Halfa people had more of the parastic worms: 26% to Kulubnarti’s 9%. However peak prevalence of infection did not occur at a younger age in the Wadi Halfa, and there was no sex difference.
Hibbs AC, Secor WE, Van Gerven D, & Armelagos G (2011). Irrigation and infection: The immunoepidemiology of schistosomiasis in ancient Nubia. American journal of physical anthropology, 145 (2), 290-8 PMID: 21469072
Note: I tried to be accurate about life in Nubia, 500AD, but please correct me in the comments
(Also, I want to be a bioarcheologist! Should I apply for one of these Graduate Programs at Emory University?
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