A baby boom among Native Americans that started some 1,500 years ago was so massive that birth rates likely surpassed the highest found anywhere in the world today, according to researchers scouring data tied to thousands of human remains found at hundreds of sites across the region where Arizona, New Mexico, Colorado, and Utah meet. It was a centuries-long rise followed by a sudden and dramatic fall, one that should serve as a warning sign about the dangers of overpopulation, the anthropologists conclude. "We can learn lessons from these people," one of the paper's authors says in a news release.
As early as 2000 BC, corn was grown in the region, though it wasn't until 400 BC that consumption of it jumped. It become the dominant calorie source, and propelled birth rates to peak levels around 500 AD, by which time Discover reports the people were utilizing "two hallmarks of civilization: settled agriculture and food storage." Per the study published in the Proceedings of the National Academy of Sciences, that birth rate then "remained at high levels with some fluctuation" for centuries. But by the mid-1100s, a terrible drought hit hard, and conflicts arose; still the birth rate stayed high right until 1280, by which time farmers seem to have had enough and fled. Within 30 years the area of 40,000 people was empty. The population may have simply grown too large to feed itself, researchers surmise, leaving behind a lesson: Overpopulation is not sustainable.