Were Ancient Humans More Resilient to Climate Change than Modern Society?
Some Archaeologists Say the Answer is Yes
By Bruce Dorminey
By studying the Paleoindian period (around 10,000 to 8,000 BC) archeologists are providing new insight into how humans have historically adapated to climate change. Credit: UTK
Given the almost constant barrage of new data suggesting a quickening pace of climate change, it’s easy to forget that the last century of our collective climate history represents only a tiny slice of a much bigger climatological pie. To learn more about the climate of the distant past, climatologists and archaeologists continue to probe the end of the last Ice Age, some 13,000 years ago, for clues to climate variability on larger scales. What they have found indicates that early humans had a tremendous capacity for adapting to sudden, wild swings in climate, but these same researchers warn that society today may have a much tougher time adapting to such changes.
Paleoclimatologists who sift through clues of earth’s past climate have primarily focused on using information gleaned from ice and sediment cores to run contemporary climate models. But some archaeologists have forged careers out of using more novel methods to study long-term changes in North America’s climate. In the process, their work has provided new guidance for tackling climate change in our own era.
Archaeological evidence can be used to buttress existing paleoclimatological models, but it can’t always be incorporated by paleoclimatologists actually constructing computer models. Also, some paleoclimatologists appear to be more open to data derived from archaeological means than others.
Still, one of the keys in studying how humans responded to previous episodes of climate change comes from the excavation of Paleo-Indian archaeological sites across North and South America.
Tom Dillehay, an archaeologist at Vanderbilt University in Nashville, Tennessee, says that archaeologists offer paleoclimatologists unique datasets. “We get the record of the human-environmental interaction through time, and give paleoclimatologists data that otherwise they can’t get,” said Dillehay. “We provide that lengthy record from multiple archaeological sites.”
This, in turn, gives climatologists an idea of which plants and animals flourished at the time, which is an important clue about climate conditions. Here’s how it works: oxygen isotopes in animal and human bones provide details about precipitation patterns of the era; nitrogen isotopes in bones indicate water stress and the region’s amount of aridity; and carbon isotopes in bones can indicate vegetation patterns.
“Teeth have enamel build up since childhood and the whole history of what you depended on [for sustenance can be accessed via the isotopic information stratified in the enamel of teeth],” said Dillehay. “That includes climatic and dietary patterns.”
Even so, archaeologists must be flexible enough in their field methodology to take their data in whatever form it presents itself — whether from ancient dental patterns to data derived from the bottom of a dry lake bed.
David Meltzer, an archaeologist at Southern Methodist University in Dallas, Texas says his work in the early 1990s at an excavation at Mustang Springs in west Texas thoroughly documents extended drought following the end of the Ice Age. Meltzer observes the varying depths of wells found at the bottom of an ancient lake bed, during an approximately 2,000-year warm and dry postglacial period dating from some 7,000 to 5,000 years ago, which is commonly referred to as the Mid-Holocene climatic optimum. The wells also provide evidence that the water table in the region may have dropped by as much as 10 feet during that time.
“There were sixty water wells of varying depths,” said Meltzer. “One of the wells was over five feet deep. But it’s often very difficult to find the fine-scale resolution in the archaeological record that will enable you to say, ‘Ok, here people are responding to significant climate change.’”
But archaeologists are making progress in fleshing out a more comprehensive snapshot of the historical climate record in the Southwest, particularly at central Texas’ Gault archaeological site. In an area now rife with weekend houses and hobby ranches, the Archaeological Conservancy now owns the 32-acre, decades-old site. Here, 40 miles north of Austin, Longhorn cattle now graze where paleolithic peoples once hunted mammoth and bison.
“The [people at Gault] were generalized hunters and gatherers who started utilizing plants on a larger scale, eating everything they could lay their hands on,” said Clark Wernecke, the executive director of the Gault School of Archaeological Research in San Marcos.
In fact, the current dig’s bucolic setting in a stand of Mexican Hat wildflowers is actually an ancient garbage heap, where millennia ago, the locals cooked bulbs of the camas plant for 24 hours at a time. In so doing, they were able to transform the camas’ raw inulin-rich bulbs from complex sugar into an edible sweet fructose. And because camas typically thrives in boggy landscapes, Wernecke deduces that 15,000 years ago, the Gault site would have had to have been a lot wetter than today.
Ditto for the Monte Verde site in southern Chile, where some two decades ago, archaeologists found the remains of 14,500-year-old, human dung-eating beetles under a peat bog. “These particular beetles [Andotypus ashworthi] are very climate sensitive and require summer temperatures of something like 68 to 75 degrees,” said Dillehay. “So, back then, the area was a cool, temperate rain forest.”
That may all sound wonderfully hospitable, but Tyler Faith, a paleoecologist at George Washington University in Washington, D.C., says that compared to what our hunter-gatherer ancestors experienced in the past – such as the last Ice Age that may have caused mass migrations of Paleolithic human populations — our modern, globalized society has yet to face truly major climate shifts.
In the event of rising temperatures, William Calvin, a neurophysiologist at the University of Washington in Seattle who studies human evolution and climate change, advocates that we become modern day cave-dwellers of a sort, building new underground hillside homes. Six feet down, he says, it’s almost a constant 55°F, since underground temperatures aren’t as subject to changes in surface temperatures.
Problem is, we lack the mobility to abandon urban life for the hillsides. Meltzer laments that today, the burgeoning human population — currently at about 6.9 billion — limits the adaptation options that are available.
Despite the constraints our large populations impose, Dillehay says we still need to be more resilient, socially, politically and technologically in order to meet the challenges climate change poses. He notes that 35,000 years ago, people were much tougher and more resilient, particularly when dealing with diseases, pathogens, and cold weather.
However, Collins asserts that for all our current technological capacity for adjustment, climate change isn’t going to be reversed. “We've had six periods of global warming in the last million years and automobiles didn't cause any of those others,” he said. “Instead, we need to be planning how to respond to the changes, whatever they might be.”
As Collins alludes to, climate change events in earth’s distant past were all natural in origin, due to the vagaries of the sun’s output, eccentricities in earth’s solar orbit, and long-term periodic variations in earth’s axial tilt. However, today’s climate change very likely has been caused primarily by our recent history of manmade fossil fuel emissions.
As Calvin, the neurophysiologist, points out, the clock is ticking on just how to handle civilization-disrupting climate change events, no matter their root cause. “Droughts can disrupt the food supply and create trouble real quick,” said Calvin. “Today, half the population lives in very large cities, so once the supply lines are disrupted, everybody's very hungry. It would not be the end of civilization, but it would be a big step down.”