Unveiling Mexico’s Mammoth DNA: Discovering an Extraordinary Divergent Lineage

Long before the Felipe Ángeles International Airport was built in northeast Mexico City, the land was rich with history. Once home to Lake Xaltocan, it hosted a variety of ancient animals. When airport construction began in 2019, workers uncovered more than 110 mammoth fossils, revealing a fascinating glimpse into the past.

Paleontologists initially thought these mammoths were similar to the Columbian mammoth (Mammuthus columbi), which roamed North and Central America. The woolly mammoth (Mammuthus primigenius), known mainly from North America, migrated from Eurasia. The origins of the Columbian mammoth were less clear—research indicated it might have evolved from a mix of woolly and steppe mammoths (Mammuthus trogontherii) between 800,000 and 400,000 years ago.

However, a recent study published in Science challenges this view. Researchers analyzed mitochondrial DNA from the mammoths excavated during the airport construction and from a nearby site in Tultepec. Unlike typical DNA, mitochondrial DNA can survive better in warmer climates, which made this analysis possible despite the difficulty of extracting usable DNA in tropical areas.

The study found a unique lineage of Mexican mammoths, named Clade 1G, distinct from other North American mammoths. Within this group, the genetic differences were surprisingly deep—comparable to the differences seen between major mammoth lineages.

The researchers proposed two theories for this genetic divergence. One suggests there were variations in the mitochondrial DNA of the ancestors before the hybridization with other mammoth species. The second theory proposes that different populations mixed at various times, creating these unique mitogenomes. The authors lean toward the first explanation.

Using radiocarbon dating, they determined that these distinct lineages existed during the Late Pleistocene, around 40,000 to 12,700 years ago. This study not only sheds light on a previously complex species but also underscores the importance of gathering ancient genetic data across varied locations to understand extinct species better.

The findings highlight Mexico’s role in mammoth evolution and suggest that even in the tropical regions, robust genomic data can be retrieved from ancient fossils. This work not only boosts our understanding of mammoth history but may also open new avenues in paleogenomics.

For more on this groundbreaking research, read the study by Eduardo Arrieta-Donato et al. in Science here. Such discoveries remind us of how much more there is to learn about our planet’s history and the creatures that once roamed it.

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