|image: Ocean Drilling Program Science Operator, Texas A&M; University|
At a time when Europe was plunged in the Dark Ages, the Mayan civilization,
thriving in what is today Mexico, Honduras, and Guatemala, was studying mathematics
and astronomy, building beautiful temples and elaborate irrigation systems,
and developing a complex writing system, as
PBSâ€™s NOVA explored. This advanced culture flourished for about
a millennium and had a peak population of more than one million. But late
in the 9th century, it seemed to vanish.
The disappearance of the Maya is a mystery that has vexed archaeologists for
some time. But while they continue to dig for clues, it is ocean researchers
who may be closest to solving this mystery.
“There have been a number of theories about what possibly caused the
collapse of the Mayan civilization,” says Konrad
Hughen, a paleo-oceanographer/geochemist at Woods
Hole Oceanographic Institution (WHOI). “And many of these theories
invoked complex sociological issues, involving warfare, or possibly famine,
or disease.” But climate changes often coincide with sudden changes
in human history, and scientists have theorized that the Mayan civilization
might have been affected by drought. So an international research team led
by Dr. Gerald Haug of the Swiss Federal Institute of Technology in Zürich
set out to explore this theory further.
|The dark and light-colored layers correspond with annual wet and dry seasons.|
image: Konrad Hughen
As reported in the journal
ocean researchers used a new high-resolution scanning technique to analyze
cores of sediment
drilled from the ocean floor of the Cariaco Basin off northern Venezuela.
The sediments have dark and light-colored layers that correspond with annual
wet and dry seasons. Within those layers, the research team detected variations
in titanium levels, which reveal the amount of yearly river runoff, which
is an indicator of rainfall. What they found was a long period with a significant
lack of rainfall over a period of 150 years. And within that time period were
three extreme droughts.
“There were three exceptionally severe drought events, lasting three,
six, and nine years, during which there was very little to no rainfall at
all,” says Hughen. “And during an already dry climate, even these
fairly short periods of nearly zero rainfall, of absent rainy seasons, could
have pushed the Mayan civilization to the breaking point.”
The droughts occurred around 810, 860, and 910 AD, dates which correspond to
the three phases of Mayan collapse corroborated by archaeological evidence.
The Mayan civilization depended on a consistent rainfall cycle to support
its agricultural production. Their primary food was maize, which they started
cultivating around 2000 BC, and maize production was their main economic activity.
So scientists believe these droughts, during which there was almost no rainfall,
probably forced the Mayan civilization to the brink of collapse by putting
a strain on their resources. Some scientists also believe that the droughts
may have undermined the power of the ruling class in Mayan society because
the established ceremonies failed to “bring back” the water during
these dry periods.
Archaeological evidence suggests that the Mayan communities in the southern
and central lowlands collapsed first because communities in the northern highlands
had access to more ground water resources. But the final dry spell seemed
to be the last straw for the Mayan people.
The Mayan civilization originated in the Yucatan around 2600 BC, and rose to
prominence around 250 AD, with the “classic” period lasting till
around 900 AD.
Hughen and Haug's work was supported by the Schweizer Nationalfonds in Switzerland, the US National Science Foundation (NSF), and by British Petroleum and the Ford Motor Company through the Princeton Carbon Mitigation Initiative.