July 1, 2014
Learning Lessons From A Failed Ancient Native American ‘Baby Boom’
April Flowers for redOrbit.com - Your Universe Online
Most of the time, when you think of "baby boomers," you probably think of people born after the end of World War II. This is not the only baby boom in recent history, for sure, and a new study from Washington State University (WSU) reveals that one of the greatest baby booms in North American history occurred among the southwestern Native Americans between 500 and 1300 AD.
WSU Regents professor of anthropology Tim Kohler said that the crash that followed this boom offers 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.
Approximately 100 years' worth of data collected from thousands of human remains collected from hundreds of sites across the Four Corners region were analyzed. Many of the remains have been returned to their resting places, but Kohler was able to use the data collected to 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, has called the transition, "one of the fundamental processes of human history."
As early as 2000 BC, maize (corn) was grown in the region. Although low productivity caused populations to respond slowly to the agricultural change, the crop provided approximately 80 percent of the caloric intake of the region. This started a rise in the crude birth rate -- meaning the number of newborns per 1,000 people per year -- which continued to rise steadily until approximately 500 AD.
There were variations in the growth across the region. For example, Sonoran Desert and Tonto Basin dwellers were more culturally advanced, with irrigation, and ball courts. Eventually, these populations developed elevated platform mounds and compounds that housed elite families. Despite this, birth rates were higher in the north and east, specifically the San Juan basin and northern San Juan regions of northwest New Mexico and southwest Colorado.
The Sonoran and Tonto populations would have encountered challenges finding new farming opportunities to support many children, according to Kohler, because corn farming requires irrigation. There might also have been harmful protozoa, bacteria and viruses in the water from canals. Population groups to the northeast, however, would have been able to expand maize production into new areas as their population numbers grew.
Despite the high populations, the birth rate began to decline around 900 AD. One of the largest known droughts in the Southwest began around the mid-1100s, which also affected birth rates. The region's carrying capacity was likely reached around this time, with limited resources and a continued population growth much like what Thomas Malthus predicted for the industrial world in 1798.
By the time all the farmers had left the region, between the mid-1000s to 1280, conflicts raged across the northern Southwest. Despite this, birth rates remained high.
"They didn't slow down—birth rates 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."
By the mid-1200s, the northern Southwest was home to as many as 40,000 people. Within 30 years, however, it was empty. Many archaeological careers have been consumed with this mysterious event. Kohler suggests that the populations became too large to feed itself as the climate deteriorated. Social unity would have been difficult to maintain as people departed the region.
The take-away from this study, according to Kohler, is that population growth has clear consequences.
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