Researchers have discovered that early human ancestors were exposed to lead for over two million years, potentially influencing brain evolution and giving modern humans an edge over Neanderthals. The study, published in Science Advances, analyzed fossil teeth and brain organoids to reveal how this toxin may have driven genetic adaptations in language-related functions. These findings challenge the idea that lead toxicity is solely a modern issue.
A collaborative study by scientists from Southern Cross University in Australia, the Icahn School of Medicine at Mount Sinai in New York, and the University of California San Diego has uncovered evidence of intermittent lead exposure in ancient hominids dating back nearly two million years. By examining 51 fossil teeth from species including Australopithecus africanus, Paranthropus robustus, early Homo, Neanderthals, and Homo sapiens, the team identified chemical 'lead bands' in the enamel and dentine. These bands indicate recurring childhood exposure from environmental sources like polluted water, soil, or volcanic activity, or from lead released from bones during stress or illness.
High-precision laser-ablation geochemistry at Southern Cross University's Geoarchaeology and Archaeometry Research Group facility in Lismore, NSW, and Mount Sinai's Exposomics laboratories confirmed these traces. 'Our data show that lead exposure wasn't just a product of the Industrial Revolution -- it was part of our evolutionary landscape,' said Professor Renaud Joannes-Boyau, Head of the GARG research group at Southern Cross University. 'This means that the brains of our ancestors developed under the influence of a potent toxic metal, which may have shaped their social behavior and cognitive abilities over millennia.'
To explore the neurological impacts, the researchers created brain organoids modeling early brain development. They focused on the NOVA1 gene, which regulates expression under lead exposure. Organoids with Neanderthal-like NOVA1 variants showed greater disruptions in FOXP2-expressing neurons in the cortex and thalamus—regions key to language and speech—compared to those with modern human variants. 'These results suggest that our NOVA1 variant may have offered protection against the harmful neurological effects of lead,' said Professor Alysson Muotri of UC San Diego. 'It's an extraordinary example of how an environmental pressure, in this case, lead toxicity, could have driven genetic changes that improved survival and our ability to communicate using language.'
The study suggests that such adaptations may have contributed to modern humans' cognitive advantages over Neanderthals. Genetic and proteomic analyses revealed disruptions in pathways for neurodevelopment, communication, and social behavior in archaic variants. 'This study shows how our environmental exposures shaped our evolution,' noted Professor Manish Arora of Mount Sinai. Today, these insights highlight the deep evolutionary roots of human susceptibility to lead, emphasizing ongoing health risks for children from industrial sources.