Researchers at MIT and Harvard have mapped approximately 14,000 former human settlements over almost 9,000 square miles in Syria — using satellites to discover changes in the soil that humans left behind. Using a combination of satellite photos from the 1960s, digital maps of the Earth's surfaces, and multispectral imaging as sources, the researchers key in on anthrosols — changes in the soil caused by human waste and the decayed remnants of primitive structures. Anthrosols change the reflective properties of the soil, allowing a specialized software program to automatically process the imagery and create the maps of human activity. In their work in Syria, the researchers were able to track settlements going back as many as 8,000 years using the technique.

The researchers also utilized elevation information culled from NASA's Shuttle Radar Topography Mission, which allowed them to estimate volume in their calculations, the assumption being that areas with greater volume must have played host to their respective civilizations for a longer period of time. The procedure the researchers utilized is being published in the Proceedings of the National Academy of Sciences, but the system has already paid dividends; several long-standing civilizations were discovered in areas devoid of rich water supplies, lending support to recent theories that, contrary to popular opinion, the presence of water is not the main driving factor in the development of a human settlement.