New findings challenge the idea that lead exposure is a modern problem
A recent study published in Science Advances proposes a provocative reversal of conventional wisdom: lead poisoning may have been a feature of the evolutionary landscape long before the Industrial Revolution. The international team behind the work argues that lead and other toxic metals could have influenced how ancient humans— including Neanderthals and early Homo sapiens — developed cognitively and socially, rather than merely reflecting modern environmental pollution.
Lead is a well-known neurotoxin today, associated with cognitive deficits and developmental problems, especially in children. The authors emphasize that there is no safe level of lead exposure, a point that remains central to discussions about public health policies. Yet the study’s authors contend that lead exposure was not solely a consequence of modern industry; it may have formed a background that shaped our ancestors’ biology over thousands of generations.
From fossil teeth to a possible evolutionary driver
Led by geo-archaeologist Renaud Joannes-Boyau of Southern Cross University, the researchers used advanced geochemical mapping to analyze fossil teeth from Neanderthals and several other ancient human species, including our own Homo sapiens. Contrary to initial expectations—that lead would be a marker of recent pollution—the team found lead signatures in ancient teeth that resemble levels seen in people born between the 1940s and 1970s, a period characterized by intensive environmental exposure to lead.
According to the study, many individuals among the ancient samples carried substantial lead burdens that would likely have affected communication and social cohesion, potentially nudging behavioral and cognitive traits in a way that influenced evolutionary trajectories. The claim is that lead’s impact on the brain might have been a force for change as populations adapted to social and environmental challenges.
Bridging genetics and ancient exposure
The researchers then turned to modern genetics and lab models to explore possible protective adaptations. They focused on a gene variant known as NOVA1, which helps shield neural tissue from lead-related damage. Humans carry a version of NOVA1 that differs from the variant found in Neanderthals and other extinct relatives. To test functional consequences, the team grew brain organoids—miniature, simplified models of the brain—from stem cells carrying different NOVA1 variants.
When organoids with the archaic NOVA1 variant were exposed to lead, the scientists observed disruptions in the activity of FOXP2, a gene integral to the development of speech and language networks in the cortex and thalamus. In organoids carrying the modern human NOVA1 variant, these disruptions were less pronounced, suggesting a potential protective effect. This observation led the authors to propose that natural selection may have favored the human NOVA1 version as a response to environmental lead exposure, with knock-on benefits for language capabilities.
Implications for language, intelligence, and survival
The idea is provocative: if lead pressure helped shape the NOVA1 variant that supports language development, then exposure to environmental neurotoxins could have indirectly steered a key aspect of what makes us human—our capacity for complex communication. As the team notes, this is not a claim about modern pollution alone, but about how ancient environmental pressures may have left a lasting genetic imprint on our species.
Scientific caution and competing views
Despite the intriguing narrative, many scientists urge caution. Critics point out that organoid models, while powerful, cannot fully replicate the complexity of brain development in living beings. Yassine Souilmi, a geneticist not involved in the study, described the link as fascinating but tenuous and largely circumstantial. She called for more direct archaeological evidence and broader genetic modeling to confirm the proposed connections between lead exposure and evolutionary change.
Supporters, however, argue that the study offers a bold framework for considering how non-genetic factors could intersect with genetic evolution. If future research corroborates some of these findings, it could enrich our understanding of how ancient environments influenced brain development, communication, and social behavior across human lineages.
What this means for our view of history
In sum, the study does not claim that lead exposure caused a single dramatic leap in human evolution, but rather that it may have contributed to a mosaic of pressures guiding the emergence of modern human traits. It opens a line of inquiry that blends archaeology, genetics, and neurobiology to explore how environmental toxins might have shaped who we are today. As with many pioneering ideas in evolutionary science, the story will continue to unfold as more evidence accumulates from fossil records, chemical analyses, and advanced modeling.
