Jan Bartek – AncientPages.com – An international study has reshaped the understanding that exposure to the toxic metal lead is mainly a post-industrial occurrence. This research indicates that our human ancestors encountered lead periodically for over two million years, potentially influencing the evolution of hominid brains, behavior, and even language development.
The study also provides insights into how humans may have outcompeted Neanderthals. It was found that brain organoid models with Neanderthal genetics were more vulnerable to lead’s effects than human brains, suggesting greater harm from lead exposure to Neanderthals.
Conducted by researchers from Southern Cross University’s Geoarchaeology and Archaeometry Research Group (Australia), the Department of Environmental Medicine at Mount Sinai Hospital (New York, U.S.), and UCSD’s School of Medicine (U.S.), this research utilized innovative fossil geochemistry, advanced brain organoid experiments, and pioneering evolutionary genetics. Together, these methods unveiled an unexpected narrative about lead’s influence on human history.
Previously, scientists believed that significant lead exposure was a modern issue linked to activities like mining and using leaded petrol and paint. However, by examining 51 fossil teeth from various hominid and great ape species—including Australopithecus africanus, Paranthropus robustus, early Homo species, Neanderthals, and Homo sapiens—the team identified distinct chemical signatures indicating intermittent lead exposure dating back nearly two million years.
Using high-precision laser-ablation geochemistry at Southern Cross University’s GARG Facility (located in Lismore, NSW) and Mount Sinai’s Exposomics state-of-the-art facilities, the researchers found distinctive “lead bands” in the teeth, formed during childhood as the enamel and dentin grew. These bands reveal repeated episodes of lead uptake from both environmental sources (such as contaminated water, soil, or volcanic activity) and from the body’s own bone stores, released during stress or illness.
“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.”
The research team conducted laboratory experiments to investigate how ancient exposure to lead might have influenced brain development. They utilized human brain organoids, which are miniature, lab-grown models of the brain, to study the effects of lead on two versions of a crucial developmental gene called NOVA1. This gene is known for regulating gene expression during neurodevelopment when exposed to lead. The modern human version of NOVA1 differs from that found in Neanderthals and other extinct hominids; however, the reasons for this evolutionary change were previously unclear.
In their study, organoids with the archaic NOVA1 variant exhibited significant disruptions in FOXP2-expressing neurons within the cortex and thalamus—regions essential for speech and language development—when exposed to lead. In contrast, this disruption was much less pronounced in organoids containing the modern NOVA1 variant.
“These results suggest that our NOVA1 variant may have offered protection against the harmful neurological effects of lead,” said Professor Alysson Muotri, Professor of Pediatrics/Cellular & Molecular Medicine and Director of the UC San Diego Sanford Stem Cell Institute Integrated Space Stem Cell Orbital Research Center.
“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, but which now also influence our vulnerability to modern lead exposure.”
Genetic and proteomic analyses conducted in this study have demonstrated that lead exposure in archaic-variant organoids disrupts pathways critical to neurodevelopment, social behavior, and communication. Notably, the altered activity of FOXP2 suggests a potential connection between ancient lead exposure and the evolutionary development of language abilities in modern humans. According to Professor Manish Arora, Professor and Vice Chairman of Environmental Medicine, “This study illustrates how environmental exposures have influenced our evolutionary trajectory.”
“From the perspective of inter-species competition, the observation that toxic exposures can offer an overall survival advantage offers a fresh paradigm for environmental medicine to examine the evolutionary roots of disorders linked to environmental exposures.”
The infographic shows lead exposure to humans in modern times versus our ancestors; how teeth fossils and brain tissue were analyzed for this study; how the modern NOVA1 gene may have protected modern humans against the undesirable effects of lead. Credit: J Gregory, Mount Sinai Health System
Lead exposure, primarily resulting from human industrial activities today, remains a significant global health concern, particularly affecting children. Recent findings highlight the deep connection between environmental toxins and human biology, suggesting that our susceptibility to lead might be an inherited consequence of our evolutionary past. Professor Joannes-Boyau emphasizes that their research not only revises the historical understanding of lead exposure but also illustrates how the interaction between genetics and environment has been influencing human evolution for millions of years.
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The study analyzed fossil teeth from regions including Africa, Asia, Europe, and Oceania using advanced geochemical mapping to detect patterns of childhood lead exposure. Additionally, laboratory experiments using brain organoids with either modern or archaic NOVA1 genes were conducted to assess lead’s impact on brain development. This research focused on FOXP2—a gene crucial for speech and language—by integrating genetic, transcriptomic, and proteomic data to construct a detailed view of how lead may have affected the evolution of hominid social behavior and cognitive abilities.
Written by Jan Bartek – AncientPages.com Staff Writer