Tiny mouse thrives at 6,700 meters, challenging altitude limits
A tiny Andean leaf-eared mouse (Phyllotis vaccarum) lives above 6,700 meters—the highest record for any mammal—thanks to enhanced thermogenic capacity and more efficient mitochondrial energy use under hypoxic conditions. The population shows little genetic structure across sea level to the summits, implying ongoing gene flow. Genomic analyses reveal selection on genes for lipid oxidation, mitochondrial function, and toxin processing, suggesting adaptation to diverse elevations and diets. Understanding these mechanisms could inform human health research into oxygen deprivation and related diseases.