In the afternoon, Neves takes me to the Hatahara site, about eight miles from Donna Stella, which contains traces of a more sedentary way of life. Here pottery shards litter the ground. At one of the site’s two excavations, the broken bits stick out from the earthen walls of a large square pit. The layers of protruding pottery are so tight and thick they look almost like wall coverings.
The Hatahara site contains traces of four separate occupations by farmers. The people of the Açutuba phase, who are thought to have come from the Caribbean coast, may have been the first to settle the area, living in villages up to five acres in size, each supporting 100 to 200people. Neves believes that they lived on fish, wild meats, palms,fruits, and manioc, a root that can grow in poorer soils year-round.Although this early culture had only rudimentary agricultural practices, Neves says, the plant and animal refuse they were leaving provided the substrate for future terra preta soils.
Helena Lima, a Ph.D. student at the University of São Paulo, is trying to pinpoint when and how this soil was used to support greater populations in the Amazon Basin. She sees a stark difference between the Açutuba phase, from 300 B.C. to A.D. 400, and the later Manacapuruphase, from A.D. 400 to 900. “The Manacapuru were the first people who really changed the soil,” she says.
The terra preta soils at Hatahara and the other sites are made from a mixture of plant refuse and animal and fish bones, along with large quantities of charcoal that were deposited after settlers used stone axes and slow-burning fires to clear forest. Such smoldering fires produced more charcoal than ash. The charcoal, soot, and other carbon remains (collectively called biochar) retained nutrients, particularly potassium and phosphorus, that are limited in tropical soils. The resulting improvement in soil fertility may have allowed the land to support a larger, more stable crop-based population, although studies of fossilized pollen have not yet revealed the specific plants they cultivated.
The next phase of settlement, the Paredão, occurred from about A.D.700 to 1200. Neves suspects that the Paredão were outsiders from the south. The occupation is peaceful, though, and the Paredão and the Manacapuru lived and traded with each other.
The Paredão exploited terra preta soils even more than their predecessors. While the initial settlers in this area may have created the dark soils by accident, William Woods, director of environmental studies at the University of Kansas, says that “at some point they recognize their importance and start to promote them.” Over time, the villages of the Paredão become larger, denser, and surrounded by agricultural fields. Populations grow into the thousands at sites ranging from 5 to 40 acres. The lack of fortification strongly suggests that the groups lived in peace.