Manure ensured the success of the world’s first cities – 12/29/2023 – Science

Chemical analyzes have revealed the secret ingredient behind the creation of the first cities ever: manure. Apparently, it was thanks to the use of fertilizers of animal origin that population clusters with up to 15 thousand people emerged and prospered for a few centuries in Eastern Europe, around 6,000 years ago.

These structures, classified as “proto-urban” or “megasites” by archaeologists, were created by the so-called Trypillia culture, whose settlements were northwest of the Black Sea, in the present-day territories of Ukraine and Moldova. Everything indicates that they reached their peak before the first cities in Mesopotamia (present-day Iraq), traditionally seen as the “cradle of civilization”.

The people of the Trypillia culture, at archaeological sites such as Maidanetske, distributed their dwellings and planting and animal husbandry areas following a concentric pattern, with rows of houses forming a ring corridor around a more open area, similar to a square or yard.

There were also larger houses, in each of the “neighborhoods” and also for the city as a whole, which seem to have functioned as something similar to a residents’ association headquarters, where inhabitants would meet periodically. There is no clear evidence of social differentiation – there appears to have been no economic, military or priestly elite.

It has long been clear that Trypillia’s culture emerged thanks to the transformations of the Neolithic, a phase in human history in which animal husbandry and agriculture transformed our species’ way of life. In a new study, published in the specialized journal PNAS, German and Ukrainian researchers examined the chemical characteristics of the remains of domestic animals and crops from the “megasites” to understand how the population there sustained itself.

The region’s population clusters emerged in an area of ​​very fertile soil, on the border between stretches of forest and steppe, but the data indicates that the natural fertility of the land does not alone explain the success of these people.

The team led by Frank Schlütz, from the University of Kiel (Germany), found signs of agricultural intensification when examining, in the organic matter of archaeological sites, the content of nitrogen-15, an isotope (variant) of the chemical element nitrogen, which is essential for the construction of proteins in the organism of animals and plants.

Roughly speaking, it can be said that nitrogen-15, as it is heavier than the most common isotope of nitrogen, tends to accumulate in the body as we move up the food chain. Therefore, plants tend to have less nitrogen-15 than herbivores in their cells, herbivores less than carnivores, etc.

Many plants, such as legumes, are able to obtain the nitrogen they need directly from the atmosphere, through bacteria that live in their roots, meaning that there is practically no nitrogen-15 in their organism.

However, the levels of the heavy isotope in the organic remains of Trypillia settlements are so high, even in the case of legumes, that they can only be explained by a constant use of manure on crops. As manure is organic matter that has already passed through the animal organism, it tends to concentrate nitrogen-15, which is absorbed by both plants and the domestic animals that feed on them.

Residents of the “megasites” raised mainly cows, but also goats, sheep and, to a much lesser extent, pigs. Their crops included cereals such as barley and legumes such as peas.

“We concluded that a large proportion of cows and sheep were raised in fenced pastures. The manure produced in this way was used to fertilize peas in particular,” Schlütz said in an official statement released by the University of Kiel.

In fact, everything indicates that the diet of the region’s inhabitants was almost entirely vegetarian, as the combination of cereals and legumes was able to provide most of their calorie and protein needs. Meat would only make up about 10% of the diet, but raising the animals was essential to fertilize the fields.

According to the team and other archaeologists, primitive cities ended up disappearing from the region around 5,000 years ago.

“Social tensions arose because of an increase in social inequality,” explains archaeologist Robert Hofmann, also from the University of Kiel. “People abandoned large-scale settlements and decided to live in smaller communities again.”