By Aminetth Sánchez
It all started with a telephone call. One afternoon in October 2019, Jesús Cantoral Herrera’s phone rang and abruptly interrupted his routine. On the other end of the line were those responsible for supervising excavations at the Santa Lucía Military Air Base in the State of Mexico. They had news for him: they had found something strange. It was not a root, nor was it an aquifer, much less an oil field. It looked like branches. Yes, they explained to the construction engineer, some branches that were deeply buried.
That call was the starting shot. Cantoral Herrera, first captain of the Army and head of the archaeological salvage committee at the Felipe Ángeles International Airport construction site, and a group of specialists from the National Institute of Anthropology and History (INAH) went to the exact site on the northern boundary of the 3,740-hectare site and located the find a few meters from the area where fuel storage tanks are to be constructed. They stopped the digging, fenced off the area, recorded the discovery, and began to put the puzzle together to find out what those pieces, buried at a depth of between two and three meters, actually were.
Soon the confusion came to an end: they were not branches, they were paleontological remains. They were the bones of a Columbian mammoth (Mammuthus columbi), from the late Pleistocene, with an approximate age of between 10,000 and 25,000 years. It is a period described by specialists as complex because of climate changes, glaciation, and deglaciation, which altered ecosystems until they led to extinctions. It was a huge specimen of the species that was distributed towards the south of the continent; larger populations have been found on the shore of Lake Xaltocan, in the Mexico Basin, said Joaquín Arroyo Cabrales, research professor in Archaeozoology at the INAH’s Laboratories and Academic Support Department.
Just a few months before the discovery, in March of this year, the Mexican Army had begun work to build the new airport just over 50 kilometers from Mexico City. They studied the terrain, made superficial prospecting tours with archaeologists, and concluded that it was very likely that they would find some paleontological artifacts, as a Columbian mammoth molar was found in the 1950s (when the air base was first built), followed by a couple more finds that were recorded in the 80s and 90s. These were just a few clues to the historical treasure they were about to uncover.
But they never suspected the size of the treasure they would find between blocks and tons of earth. Not even in their wildest dreams did they contemplate it. “What we did not expect, what we never imagined, was the quantity,” says Cantoral Herrera. “The initial project was designed to deal with up to 15 mammoth specimens.”
The mammoth found in October was the first. Following this, the figure multiplied. To date, the excavation teams have identified 147 discoveries, and the remains of more than 70 mammoths, camels, horses, bison, antelope, birds, and fish. All this, in less than 1% of the total area of the airport construction. “It’s a find that is quickly becoming the most important in Latin America, both in terms of the quantity of bone remains found, and for the contexts in which we have found them”, says Rubén Manzanilla López, member of the INAH team and head of archaeological clean-up at the Felipe Ángeles International Airport.
An unexpected number. For Eduardo Corona, one of the coordinators of the Northwest Mexico Basin Prehistory and Paleoenvironment Project at the anthropology institute, excavations are like breaking a king cake: while digging continues, there is the possibility that you’ll get the baby. “The problem between here and February 2 is going to be managing the abundance,” he says.
As none of the finds have been the same as the others, they have been organized and classified in to three different paleontological contexts. The first group are the specimens found in the same position as when they died. The second are scattered remains, and the third are isolated bones that appeared in a deeper sandy layer, possibly due to the current of a stream of water, the activity of scavengers or even, experts believe, the activities of man in making use of these species.
“What enriches the research is the great variety, and it will give researchers a lot of material to work with”, predicts the head of the construction’s archaeological salvage committee.
The northern boundary of what will be the international airport is like a minefield: people have to walk carefully across the terrain so as not to affect any of the discovery points marked with small numbered wooden stakes, and some others covered with large colored tarpaulins. Every two steps it is possible to run into one of those markers which indicates that there are bones underneath.
Taking aerial photographs has allowed the experts to mark a grid so as to be able to keep track of each find. Armed with nothing more than brushes, dustpans, buckets, and gloves, they work to unearth them one by one.
It’s not easy to excavate and remove the skulls, teeth, horns, pelvis, feet, and vertebrae. They are fragile remains that require special treatment: cleaning, the application of chemicals to harden them so that they do not degrade, bandaging and, depending on the pieces, even plaster coating and a wooden frame. “In this case, they are not fossils: there are still parts which include organic matter; this will allow us to do DNA studies of these animals,” says Manzanilla López. “The state of conservation depends on the place where the animal died.”
Once there is news of a find, the INAH Council of Archeology or Paleontology grants permission to rescue, save, or excavate the find using dental tools so as not to damage the pieces.
During the excavation process, specialists check how stable and strong the material is. In the Mexico Basin, conservation is usually between medium and poor.
To improve handling, and so that the pieces do not fall apart, specialists apply some methods and preservatives to make them harden, sometimes even in the field.
Once the preservation process is complete, the piece can be packed to be transported to a laboratory.
In the laboratory, the packaging is removed, and the preservation and restoration processes begin, so that the bone can be exhibited in a museum.
Parallel to the strengthening of the bone (which takes time to dry) the recovered materials are measured for taxonomic and anatomical identification. In addition, samples are taken for different tests.
Each unit has two to three weeks to excavate, strengthen, record, and collect samples for genetic studies. Once the materials are stabilized, they can be handled and transported to laboratories. “If you turn up and try to remove the bones without giving them that treatment, you get pure splinters. And if we handle them, they start to fragment, and, in the end, we will only have a lot of dust left behind,” explains Cantoral Herrera.
The aim is to treat them with care, because these fragments have the potential to clarify a part of the story that, until now, has been unknown. They are the pieces of the puzzle that will help to reconstruct the environment, the feeding and health conditions of this type of animal, as well as allowing us to understand why they became extinct and what their relationship with man was 25,000 years ago.
“In terms of Mexican paleontology, it is very important, and it is also very important in terms of the paleontology of the southern part of North America; almost always there is talk about what is done in the United States and other countries, but this species is worth mentioning: it did not reach South America.”
“It is a find that is already looking to become the most important in Latin America, because of both the amount of bone remains found, and the contexts in which we have found them. There are other very important places in North America, for example Rancho La Brea in Los Angeles, where we have been finding fossil remains for more than a century, but we are hoping for this to become the most important site in Latin America: right here, within the construction.”
“Archeologically, it is a important moment for everyone; it proves that in Mexico there is also a paleontological tradition and that, at many times, it was dominated by different types of species and periods. In this particular case, we are talking about the Pleistocene. This is going to be very interesting as we are going to generate different results derived from analysis of the samples.”
“One of the important points that these finds in the Santa Lucía area are providing us with is having a record of what happened in the late Pleistocene. In this sense, it also allows us to try to understand more information associated with the species other than those which can be identified through the recovery of fossils: pollen, paleosols, behaviors, or even at the paleontological level, more information about their anatomy and the biology of the species themselves.”
ART EDITOR: MANELYK GUZMÁN / WEB DESIGN: DIANA LOBERA / ANIMATION: TANIA DOMÍNGUEZ / PHOTO COORDINATION: BERENICE RODRÍGUEZ / PHOTOS: José Miguel Crespo, INAH, AFP, Reuters and Aminetth Sánchez / PALEOILUSTRATION: SERGIO DE LA ROSA / GRAPHICS: JORGE PEÑALOZA / STYLE CORRECTION: JOSÉ MANUEL LINARES