Research from Southern Cross University in Australia reveals that exposure to lead has been a significant factor in shaping the brains of our ancient ancestors, including Neanderthals. The study indicates that lead poisoning is not solely a modern issue but has been part of the human experience for at least two million years. This new understanding challenges existing beliefs about the impact of environmental toxins on human evolution.
The team led by Professor Renaud Joannes-Boyau, who heads the Geoarchaeology and Archaeometry Research Group, analyzed ancient teeth belonging to both primates and early humans. They discovered distinct lead deposits in Neanderthal molars from Payre, France, dated to around 250,000 years ago. This research highlights that 73% of the primate and hominid fossils examined exhibited signs of lead exposure, suggesting a widespread occurrence across Africa, Asia, and Europe.
Lead Exposure and Brain Development
The study utilized laser ablation mass spectrometry (LA-MS) to conduct precise elemental analyses of the fossils. The findings revealed that the lead exposure coincided with periods of tooth formation, indicating that Neanderthals were repeatedly exposed to lead, likely emanating from natural sources such as lead-rich soil or volcanic dust. In the case of the Payre sample, water from the limestone-rich Rhône Valley may have contributed to this exposure. The distinct patterns found in the teeth ruled out later contamination, confirming that lead was absorbed while the Neanderthals were alive.
The researchers connected these ancient exposures to potential neurological impacts. In modern humans, lead is known to be a neurotoxin that can impair cognitive functions, learning, and social behavior. The study highlights the role of the NOVA1 gene, which is vital for neuronal function and affects how neurons communicate. Disruption of NOVA1 activity has been linked to neurological disorders such as autism and schizophrenia.
To further investigate the effects of lead exposure, the researchers introduced lead to human brain organoids—miniature brain models—carrying a Neanderthal-like variant of NOVA1. They found that lead exposure disrupted FOXP2, a gene essential for speech and language development. Interestingly, the modern human variant of NOVA1 appeared more resilient to lead-related stress, suggesting an evolutionary advantage.
Implications for Human Evolution
The findings propose that environmental lead exposure may have influenced which genetic traits were favored throughout human evolution. Professor Alysson Muotri from the School of Medicine at UC San Diego emphasized the possible implications of these results. He noted that the NOVA1 variant in modern humans may provide protection against the detrimental neurological effects of lead exposure, potentially enhancing communication capabilities compared to Neanderthals.
As Professor Manish Arora from the Icahn School of Medicine at Mount Sinai pointed out, this study illustrates how environmental factors have shaped human evolution. The observation that toxic exposures might offer survival advantages presents a new perspective for examining the evolutionary roots of disorders linked to environmental exposures.
The research has been published in the journal Science Advances, marking a significant contribution to our understanding of how ancient environmental conditions have influenced human development. As scientists continue to explore these connections, the study serves as a reminder of the long-standing impact of environmental toxins on our evolutionary history.
