(Inside Science) -- Overcrowding, violence and environmental crisis -- these are not just modern urban problems, but ones that have plagued humanity since the advent of agriculture, as research into one of the first major farming settlements now reveals.
Agriculture began about 10,000 to 11,000 years ago in the Neolithic Period of the Stone Age. Much remains uncertain about the impacts of the shift from hunting and gathering to farming, partly because of the incomplete nature of the archaeological record.
To learn more about this revolution, scientists analyzed the Neolithic site Çatalhöyük in what is now south-central Turkey, which at its height accommodated up to roughly 3,500 to 8,000 people. First excavated in 1958, Çatalhöyük encompasses 13 hectares (about 32 acres), with deposits nearly 21 meters deep spanning roughly 1,150 years of continuous occupation.
"All the things we see now in our lifestyles -- the foods we eat, the increasing complexity of communities, the growing size of populations -- all that begins in the Neolithic," said study lead author Clark Spencer Larsen, a bioarchaeologist at Ohio State University in Columbus. "At Çatalhöyük, we can see what impacts the emergence of this lifestyle had."
The researchers investigated 742 human remains, focusing on the levels of isotopes of carbon and nitrogen in their bones. Isotopes of an element have the same number of protons, but a different number of neutrons -- for instance, carbon-12 has six neutrons, while the heavier carbon-13 has seven. The ratios between different kinds of carbon isotopes can shed light on what plants these people ate, such as wheat, barley and rye, while those of nitrogen isotopes can yield clues on how much meat these people consumed, which came from sheep, goats and wild animals.
Previous research suggested that Çatalhöyük began as a small settlement about 7100 B.C., likely consisting of a few mud brick houses. It reached its peak from 6700 to 6500 B.C. and then rapidly declined, with the site abandoned by 5950 B.C. At its height, houses were built like apartments with no space between them, "and residents probably entered and left their homes through ladders to the roofs of their houses," Larsen said.
Crowding apparently contributed to greater violence between residents -- among 93 skulls the researchers examined, 25 showed evidence of healed fractures, and 12 of these victims were injured more than once, suffering up to five blows to their heads. The scientists found the greatest number of head injuries happened when Çatalhöyük's population was at its largest and densest, suggesting that overcrowding might have elevated stress and conflict within the community.
"At Çatalhöyük, you're beginning to see developments that foreshadow what we see nowadays in life in cities," Larsen said.
More than half of those attacked were women. Most of the injuries were on the top or back of the victims' heads, suggesting they were not facing their assailants when struck. The shape of the dents in the skulls suggested the attacks came from hard, round objects, and clay balls of the right size and shape were also found at the site, which the people there likely hurled using slings, Larsen said.
The people of Çatalhöyük also experienced an increased risk of disease, most likely due to crowding and poor hygiene -- for example, while residents kept their homes mostly clean, analysis of their walls and floors revealed traces of animal and human fecal matter. Up to one-third of remains from the site's early times show signs of infections on their bones.
Animal pens and trash pits likely existed right next to some homes, which probably contributed to the spread of disease. Sheep, which can host several human parasites, also likely posed a major health risk. Moreover, plant sugars and starches promoted tooth decay, with up to 13% of adult teeth at the site showing evidence of cavities.
Changes over time in the shape of leg bones suggested that Çatalhöyük's residents walked significantly more in the site's later times than its earlier ones. This suggests its denizens had to move farming and grazing further from the site as they degraded their environment, contributing to Çatalhöyük's ultimate demise. Prior work suggested the climate in the Middle East also became drier during the course of Çatalhöyük's history, which made farming more difficult.
Still, life was not all bad in Çatalhöyük. Figurines and wall paintings were evidence of a complex society. Ancestral graves beneath house floors also attested to a prevailing sense of community -- researchers believe most people were interred under the homes in which they lived.
Unexpectedly, most members of each household may not have been biologically related. The crowns of each tooth are often highly similar across relatives, but the archaeologists found that people buried under each house were often not as similar as one would expect if they were kin.
"It's really a mystery to us," Larsen said. "The finding underscores the fact that we tend to have these biases about how things are done that come from our own culture, and that's not necessarily the way others in the world might go about things."
"This was cutting-edge bioarchaeology from a huge multidisciplinary team of specialists that all seemed to work together very well," said bioarchaeologist Jerry Rose at the University of Arkansas, who did not take part in this research. "This work serves as an inspiration, and as a vehicle for understanding archaeological remains in other parts of the Middle East where we do not have access to such large teams."
Future DNA analysis of these human remains may shed light on the relationships between members of this ancient community, Larsen said. Another step would be "to look at material from other sites in the area at the same time period and earlier and later and integrate it all into a single story of this key point in history," Rose said.
The scientists detailed their findings online June 17 in the journal Proceedings of the National Academy of Sciences.