The banks of the artificial water reservoirs in Tikal, a major city of the ancient Maya world in what is now northern Guatemala, were primarily fringed with trees and wild vegetation, according to an analysis of ancient environmental DNA.
“Almost all of Tikal’s city center was paved. That would get pretty hot during the dry season,” said Professor David Lentz, a paleoethnobotanist in the Department of Biological Sciences at the University of Cincinnati.
“So it would make sense that they would have places that were nice and cool right along the reservoir.”
“It must have been beautiful to look at with the water and trees and a welcome place for the kings and their families to go.”
Previously, scientists learned about the crops and wild plants that grew in Tikal by studying ancient pollen or charcoal.
For the new study, Professor Lentz and his colleagues developed a novel system to analyze ancient plant DNA in the sediment of Tikal’s Temple and Palace water reservoirs.
They were able to amplify small strands of DNA from chloroplasts, the plant structures where photosynthesis takes place.
Then they could match the ancient Tikal samples with the DNA of known plant species in much the same way scientists amplify ribosomal DNA to identify species of bacteria.
“The analysis was quite challenging because we were the first to do this,” said Professor Alison Weiss, a microbiologist in the Department of Molecular Genetics, Biochemistry and Microbiology at the University of Cincinnati.
“Bacterial ribosomal DNA has a database. There was no database for this. We had to take sequences one by one and search the general database to find the best match.”
The team identified more than 30 species of trees (like cabbage bark and ramón), grasses, vines and flowering plants that lived along the banks of Tikal’s reservoirs.
“Ramón is a dominant rainforest species in Guatemala,” Professor Lentz said.
“Why you would find ramón around the reservoir is a curiosity. The answer is they left this forest intact.”
“Tikal has a harsh climate. It’s pretty tough to survive when you don’t get rain for five months of the year. This reservoir would have been the font of their lives. So they sometimes would protect these places by not cutting down the trees and preserving a sacred grove.”
Among dozens of plants native to the region, the authors found evidence of wild onion, fig, wild cherry and two types of grasses.
“Grass seeds might have been introduced to the reservoir by visiting waterfowl. Grass would have proliferated at the edges of the reservoirs during dry seasons and droughts,” Professor Lentz said.
“Tikal had a series of devastating droughts. As the water levels dropped, they saw blue green algae blooms, which produce toxic substances.”
“The droughts were great for the grass but not so much for the forest plants that lived along the reservoir’s banks.”
“Were these wild areas the equivalent of a park? I think they were. I don’t know how public they would have been,” he added.
“This was a sacred area of the city surrounded by temples and palaces. I don’t know if the commoners would have been that welcome.”
A paper on the findings was published in the journal Scientific Reports.
D.L. Lentz et al. 2021. Environmental DNA reveals arboreal cityscapes at the Ancient Maya Center of Tikal. Sci Rep 11, 12725; doi: 10.1038/s41598-021-91620-6