After emerging sometime before 1000 BC, the Maya rose to
become the most advanced Pre-Columbian society in the Americas, thriving
in jungle cities of tens of thousands of people, such as the one in
Guatemala's Tikal National Park. But after reaching its peak between 250
and 900 AD, the Maya civilization began to wane and exactly why has
been an enduring mystery to scientists.
Writing in the Nov.-Dec. issue of the Soil Science of America Journal (SSSA-J),
an interdisciplinary team led by Richard Terry, a Brigham Young
University soil scientist, now describes its analysis of maize
agriculture in the soils of Tikal. Not surprisingly, the study uncovered
evidence for major maize production in lowland areas, where erosion is
less likely and agriculture was presumably more sustainable for this
community of an estimated 60,000 people.
But the team also discovered evidence of erosion in upslope soils,
suggesting that farming did spread to steeper, less suitable soils over
time. And if Maya agriculture did cause substantial erosion, the soil
loss could eventually have undercut the Maya's ability to grow food, say
the researchers.
The findings are just the latest example of how invisible artifacts
in soil -- something archeologists literally used to brush aside -- can
inform studies of past civilizations. That's because artwork and
buildings can crumble over time and jungles will eventually conceal
ancient farm fields, but "the soil chemistry is still there," Terry
says.
He explains, for example, that most forest vegetation native to Tikal
uses a photosynthetic pathway called C3, while maize uses a pathway
called C4. The soil organic matter derived from these two pathways also
differs, allowing researchers to make conclusions about the types of
plants that were growing in the soils they test.
Thus, by analyzing soils in different areas of Tikal as well as
looking at the layers that had formed in the soils, Terry and his
collaborators were able to map the areas where ancient maize production
occurred, including lowland "bajo" areas and possibly steeper slopes, as
more food was needed.
Questions like this about past farming practices have always
interested archeologists, Terry notes. But the tools of modern soil
science are now enabling these scientists to ask increasingly
sophisticated questions about how ancient peoples tried to sustain
themselves -- and whether their treatment of the land was a factor in
cases where they failed.
"[These tools] open us up to thinking about the world in ways that we
haven't before," Terry says. "We have changed the paradigm amongst the
archaeologists."
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