A worker of Mexico's National Institute of Anthropology and History (INAH) works at a site where more than 100 mammoth skeletons have been identified, along with a mix of other ice age mammals, at an area where a new international airport is currently being built, in Zumpango, near Mexico City, Mexico September 8, 2020. Scientists are unearthing more and more mammoth skeletons in what has quickly become one of the world's biggest concentrations of the now-extinct relative of modern elephants. REUTERS/Henry Romero

A worker of Mexico's National Institute of Anthropology and History (INAH) works at a site where more than 100 mammoth skeletons have been identified, along with a mix of other ice age mammals, at an area where a new international airport is currently being built, in Zumpango, near Mexico City, Mexico September 8, 2020. More than 100 mammoth skeletons have been identified spread across nearly 200 excavation sites, along with a mix of other Ice Age mammals, in the area. REUTERS/Henry Romero

Workers of Mexico's National Institute of Anthropology and History (INAH) work at a site where more than 100 mammoth skeletons have been identified, along with a mix of other ice age mammals, at an area where a new international airport is currently being built, in Zumpango, near Mexico City, Mexico September 8, 2020. Lead archeologist Ruben Manzanilla explained on Tuesday that around 24,000 years ago mammoth herds reached this spot where sprawling grasslands and lakes would have enticed them to reside. REUTERS/Henry Romero

A worker of Mexico's National Institute of Anthropology and History (INAH) works at a site where more than 100 mammoth skeletons have been identified, along with a mix of other ice age mammals, at an area where a new international airport is currently being built, in Zumpango, near Mexico City, Mexico September 8, 2020. REUTERS/Henry Romero

Mammoth bones are pictured at a site where archaeologists and workers of Mexico's National Institute of Anthropology and History (INAH) work at a site where more than 100 mammoth skeletons have been identified, along with a mix of other ice age mammals, at an area where a new international airport is currently being built, in Zumpango, near Mexico City, Mexico September 8, 2020. REUTERS/Henry Romero

An archaeologist and a worker of Mexico's National Institute of Anthropology and History (INAH) work at a site where more than 100 mammoth skeletons have been identified, along with a mix of other ice age mammals, at an area where a new international airport is currently being built, in Zumpango, near Mexico City, Mexico September 8, 2020. REUTERS/Henry Romero