A new study suggests that lead exposure in ancient humans may have played a surprising role in shaping human evolution. Researchers found that Homo sapiens might have developed a stronger resistance to the harmful effects of lead, giving them an edge over Neanderthals and other extinct relatives.
An international team analyzed the lead content of 51 fossilized hominid teeth, some of which date back nearly 1.8 million years. Notably, traces of lead were detected in 73% of the samples, which included fossils from Homo sapiens, Neanderthals, and other early hominid species.
Natural Exposure Long Before Industrial Pollution
Lead toxicity is often associated with modern sources such as fossil fuels, lead-based paints, and industrial waste. However, researchers noted that ancient hominids were also exposed through natural environmental processes.
“Volcanic emissions, wildfires, erosion, and denudation processes can lead to accumulation or dispersal into waterways,” the study explains. These natural sources could have exposed early humans and Neanderthals alike to trace levels of the heavy metal.
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Genetic Difference Between Humans and Neanderthals
The team found that both Homo sapiens and Neanderthals shared a gene known as NOVA1, which influences brain development. But the two species carried slightly different versions of that gene — a key distinction that may have affected how their brains responded to lead exposure.
To investigate, scientists created lab-grown brain organoids from stem cells, simulating ancient and modern genetic conditions. When exposed to lead, organoids carrying the Neanderthal version of NOVA1 showed disruption in another gene called FOXP2, which is crucial for speech and language development.
In contrast, organoids with the modern human variant of NOVA1 were less affected by lead, suggesting that early Homo sapiens may have evolved a form of biological resilience that helped preserve key neurological functions.
Evolutionary Implications and Survival Advantage
The study posits that this genetic difference might have contributed to the eventual dominance of Homo sapiens. By tolerating environmental toxins more effectively, early humans could have maintained healthier neurological and social function — factors vital to cooperation, communication, and survival.
While the authors caution that their research uses simplified models, they conclude that “the fossil, cellular, and molecular data support that lead exposure may have contributed to behavioral and cognitive evolution, likely affording modern humans a survival advantage.”
Limits and Future Research
The researchers acknowledge that brain organoids cannot replicate the complexity of a fully developed human brain. Nonetheless, the findings open new pathways to understanding how environmental pressures — including toxic exposure — may have influenced human cognitive evolution.
Future studies may explore how ancient genetic adaptations to heavy metal exposure still affect modern humans today, particularly in how we respond to environmental pollutants.
