First-time DNA analysis finds trees and wild vegetation around reservoirs in Tikal T.
The ancient Mayan city of Tikal was a bustling metropolis and home to tens of thousands of people.
The city consisted of streets, cobbled squares, towering pyramids, temples and palaces, and thousands of houses for its residents, all supported by agriculture.
Now researchers from the University of Cincinnati say that the Tikal Reservoirs – major sources of drinking water in the city – were lined with trees and wild vegetation that created scenic beauty in the heart of the bustling city.
UC researchers developed a novel system for analyzing ancient plant DNA in the sediment of Tikal’s temple and palace reservoirs to identify more than 30 species of trees, grasses, vines and flowering plants that lived on its banks more than 1,000 years ago. Their findings paint the picture of a lush, wild oasis.
“Almost the entire city center was paved. That would get pretty hot during the dry season, ”said paleoethnobotanist David Lentz, professor of biology at the UC’s College of Arts and Sciences and lead author of the study.
“So it would make sense that you have nice and cool places right on the reservoir,” he said. “It must have been beautiful to see with the water and the trees and a welcome place for the kings and their families.”
The study was published in the Nature Journal Scientific reports.
Lentz and his research team put forward four hypotheses as to which plants, if any, might have grown along the important reservoirs: Did the Maya cultivate crops such as corn or pumpkin there? Or did they plant fruit trees like those found on a similar reservoir at Mexico’s Purron Dam?
Perhaps they lined the reservoirs with cattails to match their nickname reed people? Lentz noticed that water lilies often adorn ancient Mayan paintings.
“Throughout Mayan iconography, water lilies represent the continuity between the water world and the world above,” Lentz said. “It was part of their mythology.”
But the researchers found little evidence to support these hypotheses. Instead, they found evidence to support a fourth idea: that the Maya allowed the embankments to remain undisturbed forest. This would have helped prevent erosion and provided medicinal or edible plants and fruits.
Researchers found evidence of a wide variety of plants living along the aquifers, including trees like cabbage bark and ramón that are 30 meters tall. Lentz said Ramón is a dominant rainforest species in Guatemala.
“Why you can find Ramón around the reservoir is a curiosity. The answer is that they left this forest intact, ”said Lentz. “Tikal has a harsh climate. It’s pretty hard to survive when it doesn’t rain for five months a year. This reservoir would have been the source of her life. Therefore, they sometimes protected these places by not cutting down the trees and maintaining a sacred grove. “
Among dozens of native plants, they found evidence of wild onions, figs, wild cherries and two types of grass. Lentz said grass seeds may have gotten into the reservoir from visiting water birds. In dry seasons and droughts, grass would have increased on the edges of the reservoirs.
“Tikal has had a series of devastating droughts. When the water level dropped, they saw blue algae blooms that produce toxic substances, ”said Lentz. “The droughts were great for the grass, but not so much for the forest plants that lived on the banks of the reservoir.”
Were these wild areas the equivalent of a park?
“I think they were. I don’t know how public they would have been, ”said Lentz. “This was a sacred area of the city, surrounded by temples and palaces. I don’t know if the commoners would have been so welcome. “
Tikal was a thriving seat of power, religion, and trade for Mesoamerica in what is now northern Guatemala, and peaked more than 1,200 years ago. Today the cultural and archaeological site is a picturesque national park surrounded by primary rainforest.
But more than 1,000 years ago the area would have looked dramatically different. Instead of rainforest, the city center would have been surrounded by the houses and fields of corn, beans, and pumpkin that would be needed to feed 60,000 people or more. At its height, Tikal was more populous than Wilkes-Barre, Pennsylvania; Atlantic City, New Jersey; or Pensacola, Florida.
Given the documented and widespread deforestation that occurred around Tikal during the rise and fall of the city, the presence of an intact forest in the city would have been noticed, said Nicholas Dunning, a geography professor at UC and co-author of the study.
“It wouldn’t have been a big park – maybe 50 by 50 meters,” said Dunning. “But it would have stood in vivid contrast to the surroundings of the central borough, which was essentially completely paved with plaster and many of the buildings were colored red.”
The reservoirs were important beyond their value as an important source of water, he said.
“Given that the Maya were a forest culture whose cosmology included many forest elements (e.g. certain sacred trees that held the sky), a sacred grove next to the sacred spring and pond in the heart of the city was an extremely powerful one Symbol – kind of like miniature pieces of the cosmos, ”said Dunning. “On the other hand, the ancient Maya cities were very green overall.”
Tikal has dwarfed today’s urban gardens.
“Away from the central district of Tikal, most of the land was either tree or grain cultivated,” said Dunning. “Almost every household complex had significant gardens. Much of the food consumed by residents of Mayan cities was likely grown in the city itself or in the immediate hinterland. Nothing like a modern western city. “
Previously, researchers learned about the crops and wild plants that grew in old Tikal by examining old pollen or charcoal, Lentz said. For their study, UC turned to next-generation DNA sequencing, which can identify plants and animals even with small strands of DNA.
“Typically, high-quality, high-concentration DNA is needed for next-generation work,” said UC botanist and study co-author Eric Tepe. “The Tikal samples were both poor quality and very low in concentration.”
Microbiologists Alison Weiss, a professor at UC’s College of Medicine, and Trinity Hamilton, now at the University of Minnesota, have set themselves the task of analyzing old microbial DNA from the sediment samples in the reservoir.
Weiss examines pathogens E. coli and human microbiomes in their lab. Her latest work examined how chemotherapy in cancer patients affects the protective lining of their digestive system. But she likes all sciences, she said, and was eager to take on a new challenge.
“DNA is ancient, so it tends to break down in short, small sequences,” said Weiss.
With the help of the Florida company Rapid Genomics, the UC scientists developed a new type of probe to select plant DNA in the sediment samples. And they were able to amplify small strands of DNA from chloroplasts, the plant structures in which photosynthesis takes place. Then the researchers could match the old Tikal samples with the DNA of known plant species, similar to how scientists amplify ribosomal DNA to identify bacterial species.
“The analysis was quite demanding because we were the first,” said Weiss. “Bacterial ribosomal DNA has a database. There was no database for that. We had to take sequences one at a time and search the general database to find the best match. “
“This project was a bit in the dark,” said Tepe. “We half expected to get no results at all. The fact that we were able to get an idea of the vegetation around the reservoirs at Tikal is, in my opinion, a spectacular success and a proof of concept that we can hopefully transfer to other Maya sites. “
UC researchers can now explore the ancient world in promising new ways.
“We are happy that we were successful,” said Weiss. “It took a long time to figure out how to do it and to make sure it wasn’t junk data, junk data out. Now it is very exciting to learn more about ancient people from these sediment studies. ”