Hunter-gatherers ignored climate change

Scientists examining an internationally important archaeological site from about 8000 years ago, which hosted an active human hunter-gatherer society for several hundred years, have found that the community experienced multiple, severe, abrupt climate changes that affected regional temperatures, the landscape and ecosystems, — but that activity at the site persisted regardless of these environmental stresses.

A British research team led by Simon Blockley of the University of London’s Royal Holloway  public research university studied lake deposits adjacent to Star Carr, a Mesolithic site in North Yorkshire, which is known for its exceptional preservation of wetland hunter-gatherer activity.

The team’s report, published in the journal Nature Ecology & Evolution, says the Star Carr population “displayed a high level of resilience to climate change, suggesting that postglacial populations were not necessarily held hostage to the flickering switch of climate change”. 

The report says that understanding the resilience of early societies to climate change is an essential part of exploring the environmental sensitivity of human populations.

Scientists are especially interested in the early part of the Holocene because it was characterised by numerous “centennial-scale” abrupt climatic changes, triggered by ice and ocean interactions as the northern hemisphere ice sheets dissipated. It was critical to the postglacial recolonisation of northern Europe.

Of these abrupt climatic changes, the report says, the impact of an event about 8000 years ago has been discussed most frequently because there is evidence that northwest Europe was widely populated by this time.

Other abrupt climatic changes are known from the early Holocene, including events about 11,000 and 9000 years ago, but there are comparatively few well-dated archaeological sites from these periods, and their impact on populations is therefore poorly understood.

Some studies have argued that hunter-gatherer communities were able to adapt to this climatic   change, but others suggest that these societies were highly susceptible and forced to abandon their lands. In particular, it has been argued that this climatic event may have caused a crash in Mesolithic populations in northern Britain and Ireland.

“These societies did not simply occupy northwest Europe,” the report says, “but were the earliest populations to attempt to recolonise this region after the last glacial period, against a backdrop of some of the most extreme abrupt climatic changes known from the Holocene. Whether these populations were resilient to such events or susceptible to the environmental changes that they triggered is crucial to understanding the patterns of recolonisation in Europe at this time.”

The Star Carr site is known for its exceptional preservation of wetland hunter-gatherer activity. It has yielded one of the largest collections of Mesolithic artefacts in Europe, the oldest evidence of carpentry in Europe, in the form of large wooden platforms, rare artefacts such as red deer antler headdresses, and the earliest evidence for built structures in Britain.

For this new study, researchers constructed a record of past environments based on previous studies of fossilised plants and animals and stable isotope ratios, and on timings from radiocarbon dating and ash from distant volcanic eruptions.

The authors correlated this record with new radiocarbon dating and archaeological data taken directly from Star Carr. Together, these high-resolution records allowed climatic events to be matched with the human activity at this site for the first time.

They found that during this time there were two abrupt climatic events, spanning only a century each. During these, temperatures dropped by 10 and four degrees Celsius respectively, with knock-on effects to local woodland growth.

Despite this climatic instability, the site occupants maintained their way of life, assisted by plentiful natural resources and by cultural adaptations.

The report says it is important to highlight that while the populations at Star Carr were resilient to the abrupt cooling of their environment, the main changes in activity at the site coincided with intrinsic changes in the local ecology, and not with the external climate itself.

It highlights that there is “far greater complexity to the story”, adding that “It is possible that, once established, the Star Carr community was buffered from the cooling effects of the second event by continued access to a range of resources, such as red deer, which are unlikely to have been adversely affected by the changes in climate and environment recorded here”.

The researchers point out that this study has not reached a finite conclusion.

“The ability to examine many individual sites across a region with similar levels of resolution is necessary to test for differences between communities and ecological settings,” they write, “and to avoid missing important details that allow us to understand the drivers behind both resilience and susceptibility to climate change.”

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