At the former habitation sites of aboriginal Indians considerable animal refuse must have been discarded close to their tents or houses. This material would have been largely composed of animal and bird bones, fish remains, and so on, rich in phosphorous. Accumulations of these wastes would have been left behind after abandoning the place, to slowly decay and percolate into the soil by rainwater.

In the humid regions, the visible evidence of such remains may have long since disappeared on an old campsite; however, the soil must have been enriched in phosphorus, and this enrichment might still be ascertainable by soil analysis.