Ancient Lead Exposure Shaped Evolution of Neanderthal Brains

Recent research indicates that lead exposure has significantly influenced the evolution of both Neanderthal and early human brains over the past two million years. A study conducted by scientists at Southern Cross University in Australia sheds light on the pervasive nature of lead toxicity throughout our ancestral history, challenging the perception that lead poisoning is primarily a modern issue.

The study’s findings reveal that lead was not merely a byproduct of industrial activities but an environmental factor that shaped brain development and social behavior in our ancestors. According to Professor Renaud Joannes-Boyau, co-corresponding author and Head of the Geoarchaeology and Archaeometry Research Group at SCU, “Our data show that lead exposure wasn’t just a product of the Industrial Revolution – it was part of our evolutionary landscape.”

Using advanced techniques such as laser ablation mass spectrometry (LA-MS), researchers analyzed the teeth of ancient primates and hominids. They discovered distinct bands of lead within Neanderthal molars from Payre, southern France, dating back approximately 250,000 years. The study found that lead exposure was present in 73% of all primate and hominid fossils examined, spanning regions in Africa, Asia, and Europe.

The presence of these lead bands corresponds to specific periods during tooth formation, indicating that Neanderthals were repeatedly exposed to lead, likely from natural sources such as lead-rich soil and volcanic dust. In the case of the Payre sample, water from the limestone-rich environment around the Rhône Valley also contributed to this exposure. Importantly, these findings confirm that the lead was absorbed while the Neanderthals were alive, as the patterns align with biological growth layers in the teeth.

The researchers also explored the potential neurological impacts of ancient lead exposure. In modern humans, lead is recognized as a neurotoxin that adversely affects cognition, learning, and social behaviors. The study highlights the role of the NOVA1 gene, which regulates neuronal activity through a process known as alternative splicing. Disruption of this gene has been linked to conditions such as autism and schizophrenia.

When researchers introduced lead to human brain organoids—miniature models of human brains—carrying an archaic Neanderthal-like version of NOVA1, they noted disruptions in the FOXP2 gene, essential for language development. Interestingly, the modern human variant of NOVA1 appeared more resistant to lead-induced neuronal stress, suggesting an evolutionary advantage for contemporary humans regarding environmental toxins.

Professor Alysson Muotri from the School of Medicine at UC San Diego commented on the significance of these findings. “These results suggest that our NOVA1 variant may have offered protection against the harmful neurological effects of lead,” he stated. This research underscores how environmental pressures, such as lead toxicity, could have driven genetic changes, enhancing survival and communication abilities in modern humans compared to Neanderthals.

Furthermore, Professor Manish Arora from the Department of Environmental Medicine at the Icahn School of Medicine at Mount Sinai in New York emphasized the broader implications of the study. “This study shows how our environmental exposures shaped our evolution,” he noted. The research introduces a new perspective on how toxic exposures might confer survival advantages, offering valuable insights into the evolutionary roots of disorders linked to environmental factors.

Published in the journal Science Advances, this groundbreaking study not only enriches our understanding of human evolution but also highlights the long-standing impact of environmental toxins on neurological development. As researchers continue to explore these connections, the lessons from our past may inform future public health approaches to managing environmental exposures.