Scientists chart an ancient baby boom—in southwestern Native Americans from 500 to 1300 AD

Jun 30, 2014
Sites like Pueblo Bonito in northern New Mexico reached their maximum size in the early A.D. 1100s, just before a major drought began to decrease birth rates throughout the Southwest. Credit: Nate Crabtree Photography

Washington State University researchers have sketched out one of the greatest baby booms in North American history, a centuries-long "growth blip" among southwestern Native Americans between 500 to 1300 A.D.

It was a time when the early features of civilization—including farming and food storage—had matured to where birth rates likely "exceeded the highest in the world today," the researchers write in the Proceedings of the National Academy of Sciences.

A crash followed, said Tim Kohler, WSU Regents professor of anthropology, offering a warning sign to the modern world about the dangers of overpopulation.

"We can learn lessons from these people," said Kohler, who coauthored the paper with graduate student Kelsey Reese.

Funded by the National Science Foundation, 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 have been repatriated, the data let Kohler 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.

"It's the first step towards all the trappings of civilization that we currently see," said Kohler. Jean-Pierre Bocquet-Appel, a French expert on prehistoric populations and guest editor of the PNAS article, has called the transition "one of the fundamental processes of human history."

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, said Kohler. But by 400 B.C., he said, 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.

Kohler said the Sonoran and Tonto people would have difficulty finding new farming opportunities for many children, since corn farming required irrigation. Water from canals may have also 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, he said.

Scientists chart a baby boom -- in southwestern Native-Americans from 500 to 1300 A.D.
This shows a reconstruction of life on a Hohokam platform mound in the Sonoran Desert in the 13th century A.D. Credit: Pueblo Grande Museum, City of Phoenix

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, with continued population growth and limited resources similar to what Thomas Malthus predicted for the industrial world in 1798.

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— were expanding right up to the depopulation," said Kohler. "Why not limit growth? Maybe groups needed to be big to protect their villages and fields."

"It was a trap," said Kohler. "A Malthusian trap but also a violence trap."

The northern Southwest had as many as 40,000 people in the mid-1200s, but within 30 years it was empty, leaving a mystery that has consumed several archaeological careers, including Kohler's. Perhaps the population got too large to feed itself as climates deteriorated, but as people began to leave, it would have been hard to maintain the social unity needed for defense and new infrastructure, said Kohler.

Whatever the reason, he said, the ancient Puebloans point up that, " has its consequences."

Explore further: No link found between low sperm count, birth defects

More information: Long and spatially variable Neolithic Demographic Transition in the North American Southwest, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1404367111

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Rustybolts
1 / 5 (8) Jun 30, 2014
"A crash followed" That would be the polite way of saying we killed them all for there land.
Vietvet
4.5 / 5 (8) Jun 30, 2014
"A crash followed" That would be the polite way of saying we killed them all for there land.


The "crash" happened long before Europeans were on the scene.
Shootist
1.7 / 5 (12) Jun 30, 2014
500 to 1300 A.D?

More evidence for the Medieval climate optimum, safely ignored by Mann's hockey stick®.

Dairy farms in Greenland.

"The polar bears will be fine". - Freeman Dyson
Shootist
1.4 / 5 (10) Jun 30, 2014
"A crash followed" That would be the polite way of saying we killed them all for there land.


The "crash" happened long before Europeans were on the scene.


Beginning of the little ice age in ca.1300 . . . killed a lot in Europe, why not North America?
supamark23
4.5 / 5 (8) Jun 30, 2014
"A crash followed" That would be the polite way of saying we killed them all for there land.


The "crash" happened long before Europeans were on the scene.


Beginning of the little ice age in ca.1300 . . . killed a lot in Europe, why not North America?


Because it was not a worldwide cooling event.
Shitead
5 / 5 (4) Jun 30, 2014
At the height of their "baby boom" the Puebloan peoples were doubling their population every 250 years, and they fell right off the Malthusian cliff. For the last century modern peoples have been doubling their populations every 40 years and we believe we can continue this forever, without consequences. Ain't god great!
Torbjorn_Larsson_OM
5 / 5 (3) Jun 30, 2014
"Why not limit growth? Maybe groups needed to be big to protect their villages and fields."

Ah. Yes, that would account for why droughts were killing off early civilizations (in America), while flooding (in Asia) didn't. "Business as usual" would help the latter, not the former.

@Shitead: Trying to make up for the 'nym, appealing to magic agencies on a science site?

Anyway, a decade ago I was more concerned about the even faster exponential drop in world population that UN saw in some projection after this century's maximum. But the latest projections has a nice leveling out, where only the aging population structure is a concern.

Malthus was tested erroneous long ago, the human population (say) generally doesn't follow his model. This is the first time I've heard of any population besides isolated bacteria that does so. Apparently it happens in large agrarian drought societies, but only there (AFAIK).
Shootist
1.4 / 5 (10) Jun 30, 2014

Because it was not a worldwide cooling event.


That's your gospel.

The facts are clear that China cooled at the same time North America and Europe cooled. The idea the the Gulf Stream did all that is ludicrous.

"And no climate model yet has any explanation for the Viking Warm period or the Little Ice Age. They are simply ignored. The Earth has been several degrees warmer and several degrees colder than it is now in historical times, and all this is documented. The notion that the Gulf Stream affected Greenland, the Western Scottish Islands, the Eastern Scottish Islands, Belgium, Germany, Poland, and China, all reporting longer growing seasons and earlier spring in the Viking era, is too absurd to consider seriously. Not that I expect rationality to prevail. There are too many grants at stake." - Jerry Pournelle

"The polar bears will be fine" - Freeman Dyson

Mayday
5 / 5 (5) Jul 01, 2014
Around 1065, the eastern flank of San Francisco Peak, near Flagstaff, blew out in an eruption. And numerous cinder cones erupted throughout the region. Almost overnight great swaths of land became uninhabitable. The growing populations were near a point where from a resource standpoint, they had almost no room for error. The eruption would have been a huge disturbance in their political and spiritual leadership as well. The mass migrations would have set off terrible warfare to the south and southeast. There is your "crash."
TheGhostofOtto1923
2.3 / 5 (3) Jul 01, 2014
"A crash followed, said Tim Kohler, WSU Regents professor of anthropology, offering a warning sign to the modern world about the dangers of overpopulation."

'7 years of feast followed by 7 years of famine.'

- If I didn't know better I would say this was evidence of precolombian contact with euro missionaries. But wait -

Construction at Macchu picchu began some 60 years before euros arrived in Peru. Priests and their families had already fled there and were safe while disease and destruction destroyers their civilization.

The civilization they had created was conveniently configured to fall with the murder of one man. Some 25k of roads, employing some 60% of the labor force, had been constructed which conveniently made it very easy to conquer and to remove all the gold.

So was this priesthood sent from Europe for the Purpose of preparing the way for invasion? And what of the incas - where did their priests flee to?

Perhaps they headed north and west, into the desert.
TheGhostofOtto1923
2.3 / 5 (3) Jul 01, 2014
Malthus was tested erroneous long ago, the human population (say) generally doesn't follow his model.
Malthus was 'tested' by sociopoliticians eager to disguise the greatest efforts at population control the world has yet seen. The world wars destroyed the religionist cultures throughout Eurasia which would have resisted the family planning programs spread shortly thereafter.

The result was ONE BILLION ABORTIONS. And hundreds of millions more prevented through birth control.
http://www.johnst...bortion/

Religions force growth. They spread by outgrowing and overrunning their neighbors. Kurds and gazans and afghans for instance will double their numbers in 16 years. By Design.

The result is what we are seeing in the Middle East as there are plenty of excess idle, hungry, young males for rioting in the streets and invading iraq. And this
http://www.unhcr....949.html

-in addition to widespread starvation, disease, and misery.
antigoracle
1 / 5 (6) Jul 03, 2014
Because it was not a worldwide cooling event.
--supamark23
Wow!!! I had no idea stupid could be this strong. The AGW Cult has found its perfect Chicken Little.
ryggesogn2
3 / 5 (2) Jul 05, 2014
"We can learn lessons from these people," said Kohler, who coauthored the paper with graduate student Kelsey Reese.

Yes, don't depend upon nature.