What an old pee can teach us about the rise of agriculture

While most would probably consider the invention of the toilet being a positive development of human history, it could be an obstacle for future researchers interested in understanding our era. Just ask the authors of a new study, published today in the newspaper Progress of sciencewho examines salts deposited in ancient urine to discover one of the most crucial transformations of humanity.

Like researchers who used poo remnants to trace the ascent and fall of Cahokia, this team used pee to describe population growth and rearing systems at Aşıklı Höyük, in present-day Turkey. The results indicate that about 10,000 years ago, the site experienced a tremendous jump among its populations of humans and some animals, including goats and sheep. The hunter-gatherer society that previously occupied the site would not have been able to achieve this type of population growth, so that the pee could signal the advent of agriculture and agriculture. domestication of animals, powerful engines of expansion and innovation.

Jordan Abell, lead author of the study and graduate student at Columbia University, says evidence from Neolithic agriculture and livestock has been accumulating in Aşıklı Höyük for years. Some of his coauthors had found that the newer and higher layers of the site contained far more sheep bones than older layers, as well as evidence of animal management practices such as the use of newborns. selective felling. Abell and his colleagues knew that a larger population would also have had to leave other clues. Realizing that "humans and animals are pissing, and when they piss, they release a pile of salt," the team knew exactly where to look next.

By studying salt levels in 113 samples – including waste, bricks and fireplaces – taken from different locations on the site and at different times in its history, the team found a considerable increase in salts in the layer of the site, which dates back about 10,000 years. . In fact, this layer had about 1,000 times the salt of older layers, even those that had been inhabited by humans. The team did the math: they estimate that, for about 1,000 years, 1,790 people and animals on average urinated daily on the site. (To confirm that the salts came from urine, the team counted the salts that would have been deposited per 1,000 years of precipitation and debris, among other factors, and found that it remained more salt.)

The study further complicates the idea that the Neolithic revolution to agriculture was launched in the Fertile Crescent, a region encompassing parts of the Middle East but beyond Turkey. Through pee, we are now closer to knowing that the inhabitants of Aşıklı Höyük enjoyed a similar sedentary lifestyle at the same time.