Giant Mammals from Mexico Uncovered as Part of a Previously Unknown Species, According to Genetic Analysis

In a groundbreaking discovery, researchers have unearthed a previously undocumented maternal lineage of mammoths, now dubbed Clade 1G, in central Mexico. The findings, published in a recent study, have challenged the prevailing belief that warm regions like Mesoamerica are a dead end for ancient DNA research.

The study, which focuses on the Columbian mammoth, Mammuthus columbi, suggests that this species may have descended from a hybridization between woolly mammoths (Mammuthus primigenius) and a Eurasian ancestor, the steppe mammoth (Mammuthus trogontherii). This hybridization theory has been proposed as a possible explanation for the sharp mitochondrial split in the Columbian mammoth.

The mammoth remains were discovered during construction works at the site of Mexico's Felipe Ángeles International Airport in 2019. Over 110 fossilised mammoth remains were found, dating between 40,000 and 12,700 years ago. Subsequent excavations at Tultepec between 2016 and 2019 added to the fossil record.

The genetic analysis of the mammoths from both sites revealed that they belonged to Clade 1G, a lineage distinct from other North American mammoth populations such as the Columbian and woolly mammoths. Genetically, this lineage reveals a more complex diversity, suggesting they adapted to warmer tropical highland climates and coexisted with other mammoth lineages in the Late Pleistocene.

The extracted mitochondrial DNA only traces the maternal lineage, but the researchers lean towards the first hypothesis: that mitochondrial diversity was already present in the woolly mammoth ancestors before hybridization. Another explanation proposed by the authors of the study is that different parental populations of woolly mammoths admixing at different times with a similar Krestovka lineage gave rise to divergent Columbian mammoth mitochondrial genomes.

This level of genetic distance is typically seen between distinct species, not individuals from the same presumed group. The discovery demonstrates the feasibility of recovering DNA from Late Pleistocene samples from tropical latitudes and emphasizes the importance of recovering ancient genomic data from wider geographical ranges to fully understand the evolutionary trajectory of extinct species.

The area where the fossils were found was once covered by Lake Xaltocan. The study challenges the notion that warm temperatures in central Mexico would hinder the extraction of viable ancient DNA, opening up new possibilities for future research in this field.

In conclusion, the discovery of Clade 1G offers valuable insights into the evolutionary history of the Columbian mammoth and challenges long-held beliefs about the limitations of ancient DNA research in warm regions. The findings underscore the importance of continued exploration and the recovery of ancient genomic data from a diverse range of geographical locations.