In today’s Science! news: Ancient baby boom reveals dangers of overpopulation. This is an article based on a press release. The study itself does not seem to be available online.
Here’s the conclusion:
According to a report (the link is to the press release) from Washington State University, researchers have described one of the greatest baby booms in North American history – a centuries-long “growth blip” amongst southwestern Native Americans stretching from 500 to 1300 A.D.
At this point in North American history, the early features of civilization had matured to where birth rates likely “exceeded the highest in the world today,” the researchers note in an article in the Proceedings of the National Academy of Sciences.
Dire. Here’s the method, as best as can be gleaned from the press release:
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.
OK, methodological question: how does one get from studying data* on human remains collected over a century, from people who lived over a period of 800 years, from an area of a couple hundred thousand square miles, to conclusions about overpopulation? I mean, it could be possible in theory if some rather peculiar information could be gleaned from the data collected on the bones – precise time frames for lifespans, nutritional history, cause of death, what percentage of the entire population from any one time the remains from that time represent, and – here’s a hard one – how representative of the entire population the remains happen to be. Why suppose that the remains are not outliers? King Tuts, as it were?
It would be fascinating to learn how the scientists dealt with these issues to reach any conclusions at all, let alone the specific conclusions they did reach, but the press release is big on telling us how much we can learn from the story of a population boom and subsequent population collapse, and not big on giving us any reason to believe those conclusions are valid in the first place. Such is modern soft science.
Well, we have conclusions to draw and grant granters to appease, so let’s get to where we’re going:
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.”
The chief consequence of population growth seems to be that there are more people. And it’s a bad idea to farm in a semi-desert environment when there is an extended drought. And violence can get, well, violent. And Malthus, who has never been proved right in broad daylight with people watching, was right all along – it’s just that we needed a pile of old bones and a (circular?) theory to explain them to prove that Malthus is right but only when nobody’s watching. Something like that.
So, there may be some science in among the Science! somewhere – but we’ll never know unless the paper makes it to the internet. I kind of doubt it. But that’s hardly the point – the proper boogeyman has been invoked, and we have all been warned – again – against having children, who are clearly the root of all evil.
* There’s a scene in the Foundation trilogy somewhere where scientists searching for proof that this mythical place called ‘Earth’ actually existed are described as doing no field work, but rather spending their time reviewing the data from earlier researchers. Some upstart suggests they, you know, *go* to the planets under consideration – which baffles the scientists, as the data has already been collected…
AFTERTHOUGHT: for those not from around here, the area under discussion is southeast Utah, northeast Arizona, northwest New Mexico, and southwest Colorado – huge area. If 40,000 people lived there as asserted, the population density would be far below 1 per square mile – closer to 0.1 per square mile. And this is where we’re looking for an ancient Malthusian collapse? I wouldn’t be surprised if 40,000 people could survive on the squirrels and pinon nuts in that area. On the other hand, there are a couple large rivers in that area – the San Juan and the Rio Grande – that have nice fertile valleys, which, were early Americans to build there, might not have left a trace, what with floods and all. So, it could be that the populations for which we have evidence – mostly, those in desolate, dry areas like Chaco Canyon and Mesa Verde – might not even represent the dominant culture or bulk of the population. Just so, the early human remains our paleoanthropologists get to play with were (and still largely are) from dry, protected areas. A huge civilization built in, say, the jungles of southeast Asia, where wood was their common building material could, in 10,000 years, vanish without a trace – not so the Egyptians and Mesopotamian civilizations, that build at least some of their buildings in dry areas off the flood plains. So, again, easy to see the panic mongering here, hard to see the science.