The enzyme AMPD1 plays a key role in muscle energy production and normal muscular function. Loss of AMPD1 activity due to genetic mutations is the most common cause of metabolic myopathy in Europeans, occurring at a frequency of nine to 14 percent.

In a study published in Nature Communications, researchers compared ancient Neandertal DNA with modern human genomes and found that all Neandertals carried a specific AMPD1 variant absent in other species. Laboratory-produced enzymes with this variant showed a 25 percent reduction in AMPD1 activity. When introduced into genetically engineered mice, the reduction reached 80 percent in muscle tissue, impairing enzyme function.

The study also revealed that modern humans inherited this variant through interbreeding with Neandertals, who inhabited Europe and Western Asia before encountering modern humans around 50,000 years ago. Today, individuals of non-African descent carry roughly one to two percent Neandertal DNA.