Ancient baby boom holds a lesson in over-population

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.

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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 — 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.”

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, “population growth has its consequences.”

We have some advantages over ancient civilizations.  The big one over the southwest native American tribes is that we have writing, so we’re not dependent on personal memories for how the climate changes over several generations.  We can keep detailed records and observe climate cycles.  We also have archaeology and the other sciences, which allow us to study the mistakes of previous societies and to detect the early effects of our own mistakes.

Of course, none of those advantages mean much if we don’t heed the information from them.  There are a number of strategies we could use mitigate population growth, but by far the most effective is promoting women’s rights.  When young women have something in life to look forward to other than motherhood, a substantial portion of them will choose alternative lifestyles.  It’s what’s already happening in Europe, Russia, and Japan.  We just need to find a way to convince the rest of the world that it’s a good idea.