A groundbreaking study led by researchers at Southern Cross University in Australia has discovered that both Neanderthals and early humans were exposed to lead for millions of years. This exposure significantly influenced the evolution of their brains and behaviors, challenging previous assumptions about the history of lead toxicity in human development.
The research indicates that lead was not solely a consequence of industrial pollution but a persistent environmental factor dating back at least two million years. “Our data show that lead exposure wasn’t just a product of the Industrial Revolution – it was part of our evolutionary landscape,” stated Professor Renaud Joannes-Boyau, co-corresponding author and Head of the Geoarchaeology and Archaeometry Research Group at SCU. He emphasized that the effects of this toxic metal may have shaped the social behavior and cognitive abilities of our ancestors over millennia.
Using an advanced technique known as laser ablation mass spectrometry (LA-MS), the research team analyzed the teeth of ancient primates and hominids. Notably, Neanderthal molars from Payre, southern France, dating back around 250,000 years, displayed distinct bands of lead, indicating repeated exposure during their lifetime. In total, lead was found in 73% of the primate and hominid fossils examined, spanning regions in Africa, Asia, and Europe.
These lead deposits correspond to periods of heightened exposure during tooth formation, suggesting that Neanderthals encountered lead from natural sources, including lead-rich soil and volcanic dust. In the case of the Payre samples, the lead likely originated from water in the limestone-rich environment surrounding the Rhône Valley. Importantly, the researchers noted that these patterns were not the result of later contamination; they aligned with biological growth layers, demonstrating that lead absorption occurred when the Neanderthals were alive.
The study also highlights the potential neurological impacts of ancient lead exposure. In contemporary humans, lead is recognized as a neurotoxin that can impair cognition, learning, and social behavior. Researchers focused on the NOVA1 gene, which plays a critical role in controlling how genes function in neurons. Disruption of NOVA1 has been associated with neurological disorders such as autism and schizophrenia.
When the team introduced lead to human brain organoids—miniature models of the brain—carrying the archaic Neanderthal-like version of NOVA1, they observed disruptions in the FOXP2 gene, which is crucial for speech and language development. In contrast, the modern human variant of NOVA1 appeared more resilient to lead-related neuronal stress, indicating that modern humans may have evolved enhanced resistance to environmental toxins.
These findings suggest that environmental lead exposure may have influenced the genetic traits favored during human evolution, potentially providing modern humans with advantages in social interaction and communication. “These results suggest that our NOVA1 variant may have offered protection against the harmful neurological effects of lead,” said Professor Alysson Muotri from the School of Medicine at UC San Diego, another corresponding author of the study.
The implications of this research extend to the field of environmental medicine. “This study shows how our environmental exposures shaped our evolution,” remarked Professor Manish Arora from the Department of Environmental Medicine at the Icahn School of Medicine at Mount Sinai in New York. He noted that the observation that toxic exposures can confer survival advantages offers a new perspective on the evolutionary roots of disorders linked to environmental factors.
The findings of this significant study were published in the journal Science Advances, marking a pivotal moment in understanding how ancient lead exposure has left a lasting impact on human brain development and social behavior.
