Wednesday, 21 August 2013

Manure and Latrines = Farming and Parasites

Pig sties are notoriously smelly places, but aged
pig manure makes excellent fertilizer.
 Image by MontagZen; CC BY-SA 3.0.

Almost twenty years ago, Jared Diamond wrote about the domestication of plants in Discover  ("How to Tame a Wild Plant," Sept 1994). "Human latrines," he wrote, "may have been a testing ground for the first crop breeders."

How so? Many plants get spread around when their seeds are eaten, passed through the digestive tract of the forager intact, and deposited in feces. Because humans tend to use latrines - designated outdoor toilets that they return to again and again - the seeds of the plants that early humans liked to eat got deposited in a concentrated area, and the wastes deposited with them provided fertilizer. Voila! Latrines would have effectively selected the choicest food items of early humans and aided their reproduction.

Because I'm interested in parasites, I couldn't help thinking that this very process also aided the transmission of intestinal parasites: choice food plants growing in areas used as latrines means people gathering food there, with resulting exposure to the eggs and larvae of intestinal worms (and probably protozoa as well).

"Our ancestors' garbage dumps," Diamond pointed out, "undoubtedly joined their latrines to form the first agricultural research laboratories." This, because larger seeds, roots and other plant parts that might reproduce would end up in the midden, or garbage dump, along with all the other food waste (think compost) and animal manure (if they had livestock), gaining a survival advantage in virtually the same way.

And now, in his article "Early Farmers and Manure: Stone Age Europeans Were More Advanced Than We Thought," (Decoded Past, July 3013) Frank Beswick reports on evidence that stone age people used animal manure as fertilizer as long ago as 6000BC. Beswick wonders "is it possible that the use of manure was a precondition of the development of agriculture?"

And I wonder how much it contributed to the parasites we share with domestic animals, particularly cattle and pigs.

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