China has a few deserts, but there is one that stands out for its aridity: in the Tarim basinin northwest China, rain round 20 millimeters a year. Seeing a landscape of dunes and rocks so barren that it seems lunar, it is difficult to think that there were rivers, wetlands and poplar forests there 4,000 years ago. And yet, as a study just showedthere was. The key to everything was in the people who lived there in the Bronze Age. More specifically, in the fossilized excrement of their animals and the remains of charcoal from their bonfires.
The discovery. The research team analyzed coprolites of multiple species of animals from Xiaohe culture sites and also charcoal left over from their bonfires. From here they obtained two pieces of information directly: what trees they used as fuel and what their animals ate. Or what is the same: what plants and trees were in the area. What is clear is that of all desert in the Bronze Age, nothing.
Why is it important. The research team proposes that this prehistoric community already practiced a sedentary way of life from the early phases of occupation of that area, which includes livestock farming. The resources offered by that wetland (fishing, aquatic plants, grasses) were sufficient to maintain that town in that territory, without the need for agriculture.
From an environmental point of view, the study provides first-hand information on what the Tarim landscape was like four thousand years ago, before aridification transformed the region. The Tarim has been characterized due to an extremely dry climate since the beginning of the Pliocene, although during the Holocene it experienced frequent fluctuations between dry and humid periods. This information is essential to model past climate change and thus better predict possible changes in Central Asia.
Context. The Xiaohe culture occupied the Tarim Basin between 2050 and 1350 BC. C. and we know her above all for their mummiesfound in the desert during the 20th century with peculiar wool and leather outfits. However, we knew more about how they buried their dead than about their organization, relationship with the environment and their economy.
In detail. The analysis revealed that 54% of the identifiable charcoals corresponded to poplars and willows and 18% to tamarisks, all of them flora typical of riverbank forests. These species are fast growing and regenerate easily, suggesting that the community exploited the forest in a more or less sustained manner for centuries. Considering the few remaining poplar trees, the team proposes that the landscape was organized into three zones: the riverine forest, riverside scrub, and beyond, the desert.
The remains of feces preserved pollen grains and phytoliths that allowed us to reconstruct both the diet of the livestock and the nature of the landscape: 83% of all that pollen came from the cattail, an aquatic plant that has historically been used as food, fiber, and even as construction material. In the case of sheep poop, the percentage rose to 99%, a figure so high that the team explains that it is probably because the animals ingested the pollen by drinking water laden with it or by breathing the air during flowering.
Yes, but. The first limitation to consider is that it is not always possible to know with certainty which animal each excrement comes from and that is not a trivial matter: not knowing how to differentiate between a sheep, a goat or a camel can be a great condition on its use. On the other hand, the large presence of cattail pollen may be misleading: this plant produces large quantities and resists degradation well, so the real landscape could have had more diversity than the data suggests. The question that remains unresolved is whether the Xiaohe people grew food from the beginning or not. Current evidence suggests not, but not finding them doesn’t mean they didn’t exist.
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