Our ancestors used to be hunter gatherers but eventually transitioned to herding. Researchers have used the salty residue of Neolithic urine from Turkey to know when humans switched from being primarily hunters to herding animals.
Ancient Settlement Aşıklı Höyük
Earlier studies found signs suggesting that the inhabitants of the ancient village of Aşıklı Höyük in Turkey kept animals. Animal bones and dung at the site show that the residents of the settlement were among the first people in the world to domesticate sheep and goats.
In a new study published in Science Advances, Jordan Abell, from Columbia University, reconstructed the density of humans and animals at Aşıklı Höyük over a period of 1,000 years by analyzing urine salt collected from the site.
They collected 113 samples from trash piles, bricks, and hearths from different time periods to look for pattern in the levels of sodium, nitrate, and chlorine salt.
Urine Salts Indicate Increase In Settlement's Population
Analysis revealed the abundance of urine salts increased over time, but the researchers, found that about 10,000 years ago, salt levels increased by about 1,000 times. This indicates a rapid increase in the number of occupants at the site.
The researchers in particular found that the population of people and animals that occupied the ancient settlement during this period increased from near zero to about one person or animal for every 10 square meters.
More Inhabitants Than Number Of People Settlement Buildings Could Accommodate
Although it is not possible to distinguish urine salts from humans and animals, it is still possible to use the urine salt analysis to estimate the abundance of sheep and goat.
Over a millenia, the researchers calculated that about 1,790 people and animals lived and peed on the settlement every day.
The estimated number of inhabitants though appears to be higher than the number of people that archaeologists think the settlement's buildings would have accommodated.
"Dung and midden layers at Aşıklı Höyük are highly enriched in soluble sodium, chlorine, nitrate, and nitrate-nitrogen isotope values, a pattern we attribute largely to urination by humans and animals onto the site." the researchers wrote in their study.
"We present an innovative mass balance approach to interpreting these unusual geochemical patterns that allows us to quantify the increase in caprine management over a ~1000-year period."