An area in the Mexican State of Tultepec slated to become a landfill has held a long-buried surprise: the largest prehistoric mammoth hunting site ever to be found in the country, complete with more than 800 bones from 14 individuals dating back 15,000 years.

Archaeologists with the National Institute of Anthropology and History (INAH) have been excavating the site for 10 months. They call its discovery a “watershed” moment that serves as a “touchstone on what we imagined until now was the interaction of hunter-gatherer bands with these enormous herbivores,” said INAH Coordinator of Archaeology Pedro Francisco Sánchez Nava in a statement.

Named Tultepec II, the entire excavation site measures 40 by 100 meters (131 by 329 feet). Within it, archaeologists observed stark vertical cuts in the layers of the Earth that contain two traps with almost 90-degree walls, each measuring 1.7 meters (5.6 feet) by 25 meters (82 feet) in diameter. Used for an estimated 500 years, the traps were likely visited by 20 to 30 hunters that used burning torches and branches to separate individual mammoths from their herd and push them into the pits.

At least 824 individual bones have so far been found at the “Mammoth Megasite”, including eight skulls, five jaws, 100 vertebrate, 179 ribs, 11 scapulae, five humeri, a pelvis, femurs, tibiae, and other “small” bones.

Archaeologists working at the site say that the discovery adds to our understanding of how North America was impacted during the Ice Age and changes our perception of how ancient people hunted mammoths. Markings on the bones show that ancient hunters used nearly every part of the animal, eating the organs and using bones for knife-like tools. Not only were the first settlers of the Basin of Mexico socially organized people who used the environment around them to hunt the giants, but healed wound marks on the bones indicate they may have hunted the same animal for several years before killing it. Furthermore, the unique placement of some of the bones suggests the animal may have held a ceremonial purpose in society. 

During their lifetime, these hunter-gatherers would have seen great climatic instability. As the world shifted out of the Pleistocene and into the Ice Age, the planet’s poles froze, causing sea levels to drop across the globe, including the Mexican Basin. To survive, early inhabitants of the region built traps in the clay of Xaltocan Lake as its shoreline receded, leaving its great plains exposed 15,000 years ago. Right around the same time, expansive ash from the eruption of Popocatepetl forced animals and humans to move northward. Volcanic ash found in the clay surrounding the mammoth bones has allowed researchers to date the remains accurately.

Also found at the excavation site were a camel jaw and a horse molar. Researchers say this discovery is just the “tip of the iceberg”. They intend to continue excavating the site in order to understand its full use as well as to explore similar reports in the area.