Researchers have uncovered evidence that ancient hominids were exposed to lead as early as two million years ago, potentially influencing brain evolution. Modern humans possess a unique genetic variant in the NOVA1 gene that shielded them from lead's toxic effects on language development. This discovery, published on October 15, 2025, suggests it gave Homo sapiens an advantage over Neanderthals.
Scientists at the University of California San Diego School of Medicine, collaborating internationally, analyzed fossilized teeth from 51 hominids across Africa, Asia, and Europe. The samples included modern and archaic humans like Neanderthals, early ancestors such as Australopithecus africanus, and extinct great apes including Gigantopithecus blacki. Lead traces appeared in 73% of the fossils, with 71% of human samples contaminated and the highest acute exposure in G. blacki teeth dating back 1.8 million years.
Previously, significant lead exposure was thought to begin in the Roman era with lead pipes or during the Industrial Revolution, declining only in the late twentieth century. However, the study revealed patterns in mid-twentieth-century teeth similar to ancient fossils, suggesting early hominids encountered lead while seeking water in caves. "We stopped using lead in our daily lives when we realized how toxic it is, but nobody had ever studied lead in prehistory," said corresponding author Alysson Muotri, Ph.D., professor of pediatrics and cellular & molecular medicine at UC San Diego.
Lead disrupts brain growth, impairing intelligence and emotional regulation. The team focused on the NOVA1 gene, which regulates neurodevelopment. Modern humans carry a version differing by one DNA base pair from Neanderthals'. Using brain organoids, researchers found the archaic variant accelerated maturation but reduced complexity, especially under lead exposure, altering FOXP2 activity—a gene essential for speech. "These type of neurons related to complex language are susceptible to death in the archaic version of NOVA1," Muotri explained.
This variant likely protected modern humans, fostering language and social cohesion for an evolutionary edge. Muotri speculates it contributed to Neanderthal extinction around 40,000 years ago. "Language is such an important advantage, it's transformational, it is our superpower," he said, enabling societal organization absent in Neanderthals. The findings, published in Science Advances, also inform neurological disorders like autism and speech apraxia.