The prehistoric people developed a rich agriculture in Atacama with natural fertilizers
SÃO CARLOS, SP (FOLHAPRESS) – Centuries before contact with Europeans, indigenous groups transformed part of the Atacama Desert in Chile into a rich agricultural area, where it was possible to harvest abundant corn, pumpkin and beans. The secret to such productivity was the use of guano, a natural fertilizer that the natives obtained from the Pacific coast. This surprising scenario of intensive pre-Columbian agriculture is being rediscovered thanks to the particular chemical composition of desert cultures. Vegetables grown in Atacama, a study that just appeared in the science journal Nature Plants shows, has a distinctly marine signature on their nitrogen atoms – which makes sense when you consider that guano is nothing more than the accumulation of feces from the consumption of fish by birds. This chemical signature, moreover, is even reflected in the composition of the bones of people who lived in the desert around the year 1000, said study coordinator Francisca Santana Sagredo, from the School of Anthropology of the Pontifical Catholic University of Chile. . “The levels are similar to those of the Inuit [popularmente conhecidos como esquimós, que só comiam animais marinhos]- and they are even higher, “she says. Food production in prehistoric Atacama was already known to archaeologists. According to the researcher, a factor that allowed agriculture in the area was the presence of rivers in some valleys. desert, as well as water sources in oases and some underground sources. “It is also likely that agricultural activity took place in areas which are now more arid, but which had water in the past,” She explains. The availability of sources, however, does not solve another crucial problem in the region: the lack of nutrients in the soil. To remedy this, it would be possible to use, for example, manure from lama, an animal domesticated around 4000 years ago by the Andean peoples, however, there is every indication that this was not the case. Atacama’s “magic ingredient” in agriculture. The key to reaching this conclusion is the nitrogen-15 content, a variant p The heaviest of the chemical element (its normal and lighter form is nitrogen-14 – the difference is that nitrogen-15 carries an extra particle in its nucleus). It turns out that nitrogen-15 tends to accumulate more and more in the body as it rises in the trophic level – that is, from plants to herbivores, from herbivores to carnivores that feed them. eat, from those carnivores to the carnivores that eat them. etc. The presence of nitrogen 15 in crop plants and human skeletons in Atacama is so high that it would be impossible to explain it with the use of faeces of llama (a simple herbivore) as a fertilizer. But it is fully compatible with the use of guano. Precisely because it is derived from the droppings of aquatic birds, which usually eat carnivorous fish inserted in a complex marine food chain, the fertilizer is very rich in nitrogen-15. To gain access to the resource, the inhabitants of the desert probably had to fit into a regional trade network that crossed about 100 km of territory to the coast, reaching islands with large colonies of birds like pelicans and boobies (see infographic), main “producers” “of guano. The control of the transport and distribution of fertilizers must have contributed to the formation of complex societies, with hierarchies and inequalities and a relatively high demographic density, explains the Chilean researcher. what is curious is that the Atacama system foreshadowed something that would gain globally in the 19th century. Before the invention of artificial fertilizers, guano from Chile, Peru and other parts of the world was become a coveted agricultural resource around the world, known as “white gold”.