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Science A-Go-Go
 Contrary
to common beliefs, societal collapses of the past have been caused
by sudden climate change, not only by social, political and economic
factors, Yale anthropologist Harvey Weiss reports in a new study
published in this week's Science.
"Our
conclusions are both surprising and challenging because in the
past, archaeologists and anthropologists have commonly explained
collapsed societies as the result of social, economic and political
forces combined," said Weiss, professor of Near Eastern archaeology
at Yale.
For their
study, Weiss and his colleague, Raymond S. Bradley of University
of Massachusetts, Amherst, summarized and synthesized recent archaeological
and paleoclimatological research. This allowed them to understand
that repeated incidents of societal collapse in the archaeological
and historical past have been the product of abrupt, natural climate
changes.
"These
data force a change in some general social science understandings,"
said Weiss. "The data are also important because they underscore
the difference between past climate changes and present-future
climate change. Past climate changes were unrelated to human activities.
In contrast, present and future climate change will involve both
natural and anthropogenic forces and will be increasingly dominated
by the latter."
The climatic
events Weiss describes in the study were abrupt, involved new
conditions that were unfamiliar to the inhabitants of the time,
and persisted for decades or centuries. They were therefore highly
disruptive, Weiss said, leading to societal collapse-an adaptive
response to otherwise insurmountable stresses.
The study
describes well-documented examples of societal collapse dating
back to about 12,500 to 11,500 years ago with the Natufian communities
in southwest Asia. This community suddenly abandoned seasonally
nomadic hunting and gathering activities that required relatively
low inputs of labor to sustain low population densities and replaced
these with new labor-intensive subsistence strategies of plant
cultivation and animal husbandry.
Weiss said
a major difference from the past is that we are now able to foresee
the results of these climate changes and are able to understand
the technological and social innovations which could allow us
to address them.
"We also
know where the population growth will be greatest," Weiss
adds. "We must use this information to design strategies
that minimize the impact of climate change on societies that are
at greater risk. This will require substantial international cooperation,
without which the 21st century will likely witness unprecedented
social disruptions."
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