| News / Science News |
Scientists chart a baby boom in southwestern Native Americans from 500 to 1300 A.D.
NSF | JULY 3, 2014
Scientists have sketched out one of the greatest baby booms in North American history, a centuries-long "growth blip" among southwestern Native Americans between 500 and 1300 A.D. It was a time when the early features of civilization--including farming and food storage--had matured to a level where birth rates likely "exceeded the highest in the world today".
The ruins of a village built by Hohokam Puebloans about 1000 years ago. Image Credit: Tony the Marine/Wikipedia (CCA-SA 3.0)
Then a crash followed, offering a warning sign to the modern world about the dangers of overpopulation.
The study looks at a century's worth of data on thousands of human remains found at hundreds of sites across the Four Corners region of the Southwest.
While many of the remains studied have been repatriated, the data let scientists assemble a detailed chronology of the region's Neolithic Demographic Transition, in which stone tools reflect an agricultural transition from cutting meat to pounding grain.
Maize, which we know as corn, was grown in the region as early as 2000 B.C.
At first, populations were slow to respond, probably because of low productivity. But by 400 B.C., the crop provided 80 percent of the region's calories.
Crude birth rates--the number of newborns per 1,000 people per year--were by then on the rise, mounting steadily until about 500 A.D. The growth varied across the region.
People in the Sonoran Desert and Tonto Basin, in what is today Arizona, were more culturally advanced, with irrigation, ball courts, and eventually elevated platform mounds and compounds housing elite families.
Yet birth rates were higher among people to the North and East, in the San Juan Basin and northern San Juan regions of Northwest New Mexico and Southwest Colorado.
The Sonoran and Tonto people eventually would have had difficulty finding new farming opportunities for many children, since corn farming required irrigation. Water from canals also may have carried harmful protozoa, bacteria and viruses.
But groups to the Northeast would have been able to expand maize production into new areas as their populations grew. Around 900 A.D., populations remained high but birth rates began to fluctuate.
The mid-1100s saw one of the largest known droughts in the Southwest. The region likely hit its carrying capacity.
From the mid-1000s to 1280, by which time all the farmers had left, conflicts raged across the northern Southwest but birth rates remained high. They didn't slow down. Birth rates were expanding right up to the depopulation. Why not limit growth? Maybe groups needed to be big to protect their villages and fields. It was a trap, however.
The northern Southwest had as many as 40,000 people in the mid-1200s, but within 30 years it was empty, leaving a mystery.
Perhaps the population had grown too large to feed itself as the climate deteriorated. Then as people began to leave, that may have made it harder to maintain the social unity needed for defense and new infrastructure.
Whatever the reason, he says, the ancient Puebloans show that population growth has clear consequences.
YOU MAY ALSO LIKE
