|March 27, 2018|
11,000 years ago, our ancestors survived abrupt climate change
|Imagine if, instead of heat this summer, we were faced with a sudden, dramatic cold front that lasted the next 100 years. That is what our hunter-gatherer ancestors lived through 11,000 years ago.|
Findings from a Middle Stone Age site named Star Carr in North Yorkshire, England, show that our ancestors resiliently survived the century-long drop in temperature, according to a new study in the journal Nature Ecology & Evolution on Monday.
How they responded to such abrupt climate change could hold key insights for us as we face a different kind of climate change, the researchers said.
Ancient climate change
Paleoclimatologists, who study climates of the past, know that Earth's climate was not as stable for our ancestors as it has been for us.
These abrupt, harsh changes could mean life or death, often forcing whole populations to move if they wanted to survive.
For example, one well-studied event 8,200 years ago was a sudden cold shift that lasted over a century, recorded in Greenland ice cores and within the fossil record across Europe, the researchers said. It occurred when the North American ice sheet decayed after the last ice age and released meltwater into the North Atlantic Ocean, disrupting the currents that brought heat to Western Europe. This triggered large-scale population crashes in northern Britain and large cultural changes in southern Europe, they said.
In studying the Star Carr site, the researchers learned that two events there 9,300 and 11,100 years ago resulted in temperature decreases of 10 and 4 degrees Celsius.
"The population at Star Carr, some of the earliest people to recolonise Britain after the last ice age, must have been highly resilient to climate instability, capable of persevering and maintaining a stable society in spite of these environmental stresses," Ian Candy, study author and professor of geography at the Royal Holloway University of London's Centre for Quaternary Research, wrote in an email.
"These conclusions really change the way that we think about the interaction between prehistoric societies and climate change. The abrupt climatic events seen at Star Carr are as large, if not larger, in magnitude as the (event 8,200 years ago) and yet here we confidently show that the populations at Star Carr were resilient to the impact of such events.
"These hunter-gatherers had a lot of skills and knowledge of how to use the natural resources. They could make shelters and houses and hunt, fish and collect plant materials. It must have been a lot colder and harsher conditions to live in but they had structures and used fires to keep warm, and seem to have had access to animals such as red deer."
The climate change would have cooled both summer and winter temperatures. This also would've affected the landscape and caused it to be more unstable, pausing the development of the woodland environment the hunter-gatherers depended on.
During the first event, the site was populated on only a very small scale. The researchers have no way of knowing whether the climate change event was the cause of this.
But during the second event, Star Carr was a home to many hunter-gatherers, and despite the climate shift, they did not change their way of life or abandon the site. And according to the researchers, red deer -- which provided the people with skins, meat and other products -- would not have been affected by the temperature change, meaning the hunter-gatherers still had access to them.
Why Star Carr?
Star Carr has been a treasure trove for researchers from around the world since it was first excavated in the late 1940s. This site, at the edge of a former lake basin, includes the oldest evidence for carpentry in Europe: large wooden platforms made from wood worked with flint tools.
Eleven thousand years ago, it would've been open landscape made up of grasslands, shrub and woodlands.
It is also the site of the earliest evidence for built structures in Britain, including raised circular wooden structures thought to be houses. And rare artifacts, like a plentiful number of red deer antler headdresses and masks, are intriguing.
Bones, flints, shale beads and antler headdresses have been recovered at what would've been in the lake's edge of these former wetlands. The reed swamp would've been rich in plants and animals, before the standing water became more shallow and boggy.
The peat has helped preserve the artifacts, but it's deteriorating as the water table changes.
The researchers were assessing the damage done at the site due to these changes and racing to recover artifacts before they were lost, Candy said.
"At the moment this site remains unique because of the wealth of data found there," Candy wrote. "We have now found over 30 antler headdresses from the site -- there are no other sites in the UK where these have been found and only a few are known from a couple of sites in Germany: so they are extraordinarily rare. It is not often you find sites with this level of preservation -- usually only the stone tools survive -- and whilst stone tools can still tell us a lot about past lives, the organic remains provide a much more detailed picture."
The researchers discovered the detail of the climate change events by building a record of what happened at the site. Lake deposits, fossilized plants and animals, radiocarbon dating, ash from volcanic eruptions and other archaeological data allowed them to match the climate record alongside human activity at the site for the first time.
But they didn't find human bones, which leaves the researchers wondering how these hunter-gatherers dealt with their dead.
The findings at Star Carr change how the researchers look at hunter-gatherer populations.
"Generally it was thought that hunter gatherers were fairly mobile," Candy said. "We now know they built structures very early on after the end of the Ice Age, and that they were fairly settled.
"The antler headdresses are most intriguing. They seem to have been used and deposited in the shallow waters both during the climatic downturn and after it.
We can't ever be sure what they were used for, but a lot of work has gone into making them and from ethnographic analogy one possibility is that they were used by shamans as part of their costumes."
Climate change, then and now
Resilient ancestors who could survive climate change events and cope with extremes sounds promising -- but there are other factors to consider when looking ahead to our own changing world, Candy said.
"The total population and the density of these prehistoric populations would have been tiny in comparison to Britain at the present day," Candy said. "Our current population puts a much greater pressure on the resources that we are reliant on, many of which will be effected by future climate change. Furthermore, the people of Star Carr were part of a tradition that had experienced dramatic climate shifts at the end of the last age, extreme climatic instability was part of their way of life. In contrast, our society has existed through many centuries or even millennia of stable climates, we have no experience of sudden large-scale change."
Whereas our ancestors lived through transformations of landscape and ecology, climate change would impact many more things that affect our daily life, said Sam White, history associate professor at The Ohio State University. White, who has written about environmental and climate history, was not affiliated with the new study.
"For our modern society, there are so many more people at risk and more vulnerabilities to consider: modern infrastructure and cities at risk of rising sea levels, agriculture unsuited for warmer seasons and more drought, moving disease vectors, lost biodiversity and ecosystem services, and so on," White wrote in an email. "It's good to hear stories of adaptation and resilience, and not just crisis and collapse. But we need to be cautious with either."
Mark Carey, a professor of history and environmental studies at the University of Oregon, pointed out that it's key to focus on the fact that societal change and climate change are a complex relationship, and that societal changes are not always in direct response to climate change.
"Such analyses of past climate-society dynamics can illuminate where and why problems emerged or successes occurred in response to abrupt climatic changes, such as this case at Star Carr," said Carey, who was not involved in the new research.
"The depth of archaeological and climatic evidence presented in this study takes us in a positive step to show how societies adjust in the face of abrupt climatic change. It also sets up the next level of research to probe decision making and cause-effect dynamics, allowing researchers to go beyond the correlation of events (climate change and societal change) and toward causal explanations for how and why societies persevere in the face of climate change."
Dagomar Degroot, professor of environmental history at Georgetown University and co-founder of the Climate History Network, is among the researchers finding evidence of resilience in the face of past climate change events.
"Studies of this kind show correlation much better than they reveal causation, so it's difficult to know how exactly the people of Star Carr successfully endured even the most extreme climate changes," wrote Degroot, who was not involved in the study, in an email. "Still, these dramatic results suggest that, in the wake of the great Ice Ages, past climate changes rarely determined the course of human history in a straightforward way. In my opinion, this article has great significance for our understanding of anthropogenic global warming."
Though climate change will play a major role in shaping our future, humans are also adaptive and capable of rapid solutions, Degroot said.
"With that said, vulnerability to climate change is about the scale and speed of climate change, on the one hand, and the characteristics of a society, on the other," he said. "In this last sense, our plight is most different from that of our ancestors at Star Carr. We live well beyond the carrying capacity of our planet, in ways the resilient inhabitants of Star Carr certainly didn't."
Only time will tell regarding our own future response to the various impacts of climate change.
"Whether we have the potential to show the same resilience to sudden extreme climate change as the people of Star Carr is yet to be tested," Candy said.