Mammoth Megafind near Mexico City Airport Reveals Ancient DNA and Cross-Border Pollution Insights

Short Summary

This episode highlights a landmark paleontological find near Mexico City where salvage excavations uncovered hundreds of mammoth bones, other megafauna, and the first ancient DNA from Colombian mammoths in a warm climate. The conversation explores how archaeologists, aided by a military-funded project, revealed a sprawling lake basin’s fossil record, the implications for megafauna extinction theories, and the long-term need for paleontology training. The show also investigates the Tijuana River pollution crisis, showing how water contaminants become airborne pollutants that affect air quality far from the source, and ends with a discussion of the philosophical questions about animal death in Susannah Monso’s Playing Possum.

Mexico City Megafossil Find

The podcast opens with Rodrigo Perez Ortega detailing a rare megafauna discovery outside Mexico City tied to a politically charged airport project. Salvage excavations, conducted by archaeologists under military funding, unearthed thousands of bones from mammoths, camels, horses, ground sloths, saber-toothed cats, dire wolves, birds, and even a single human. The site, once a lake, yielded bones that are variably articulated or mixed due to lake-level fluctuations over thousands of years, dating from roughly 40,000 to 11,000 years ago. The scale was astonishing: hundreds of mammoths and other megafauna, with estimates suggesting around 500 mammoths, 250 camels, and dozens of other species imprinted in a vast fossil record.

“This was a mega find of megafauna.” - Rodrigo Perez Ortega

Ancient DNA from Mexican Colombian Mammoths

One of the study’s headline achievements was extracting ancient DNA from mammoth teeth and tusks, enabling 61 mitochondrial genomes to be sequenced. The work, led by Federico Sanchez Quinto of UNAM, involved a sterile, field-to-lab workflow in a military barracks-turned-lab. The results revealed that Mexican Colombian mammoths formed a distinct lineage, indicating long-term isolation and a smaller, less diverse population compared with northern mammoths. Isotope analyses showed a mixed-feeding diet, suggesting adaptation to local C3 and C4 plant resources.

“they were able to obtain DNA from 61 mammoths, effectively doubling the amount of Colombian mammoth DNA samples.” - Federico Sanchez Quinto, UNAM

Toward Understanding Megafauna Extinction

Researchers weigh how human predation and climate change contributed to extinction. The Mexican mammoths, while diverse and locally adapted, still went extinct, albeit with different population dynamics than their northern counterparts. The discovery supports a nuanced view that climate shifts and human activity interacted differently across landscapes. Ongoing analyses, including disease pathologies and population histories, aim to refine how extinction timelines are interpreted, and how diet and environmental change shaped resilience or vulnerability.

Funding, Museums, and Ongoing Work

The project spurred a large museum and research facility on a military base, but funding has since waned, slowing cataloging and curation. The team envisions decades more work as they digitize and compare thousands of bones, seeking collaborations with national and international partners to unlock further insights about megafauna in warm climates and broader paleogenomics.

Tijuana River Pollution and Air Quality

Nazifa Ahmed reports on the cross-border river pollution that spills into the Pacific and governs air quality across Southern California. Hydrogen sulfide can reach dangerous atmospheric levels and, crucially, water quality can drive air pollution far from the river itself.

“80% of these factories are US owned.” - Dr. Kimberly Prather

Towards Solutions and Public Health

The discussion emphasizes that upstream pollution control and cross-border cooperation are essential. The paper highlights a hotspot where a water column drop releases hydrogen sulfide into the air, and notes the value of air purifiers for households during high-pollution nights. The segment ends with reflections on how public awareness and policy cooperation can reduce exposure to this complex mixture of gases and aerosols.

Playing Possum and the Animal Mind

Angela Saney and philosopher Susannah Monso discuss Playing Possum, a meditation on how animals understand death, emphasizing continuities and differences in death-related cognition across species and warning against anthropomorphism while acknowledging maternal grief, primate funerary behaviors, and the enigmatic responses of other animals to death.