Case Study on the Power of Dung: The Incas

Interesting article about how the Incas used llama manure as fertilizer on a large scale: http://www.newscientist.com/article/dn20495-llama-muck-and-maize-revolution-drove-inca-success.html

Migrating grazers will follow the food.  The wild herds were much larger than the domesticated herds.  If that region was part of the annual migration pattern, the Incas would have noticed the greater fertility of the region.  The herds may also have migrated there due to hunting pressures elsewhere.

Takeaway point of the article:

"The droppings would have made all the difference to the advance of civilisation, says Chepstow-Lusty. "The widespread shift to agriculture and societal development was only possible with this extra ingredient – organic fertilisers on a vast scale."