### Lead exposure from our early ancestors
But is that really the case? To test this, Boyau and his team examined 51 fossil hominid teeth from the last two million years for lead contamination. The teeth came from great apes, pre-humans such as Paranthropus and Australopithecus, Neanderthals and homo sapiens from Africa, Asia and Europe. Modern research has shown that lead is permanently deposited in the layers of tooth enamel when children are exposed to increased levels of lead during tooth growth.
The surprising result: “We found clear signs of increased lead contamination in 73 percent of the samples,” reports the team. Even teeth from more than a million years ago showed lead-containing “growth rings,” reflecting repeated periods of increased stress. The lead levels were similar to those in the teeth of US children born in the era of leaded gasoline, comparative analyzes showed.
These results prove that our early ancestors were repeatedly exposed to increased levels of toxic lead. Lead poisoning is thus not a modern phenomenon, but rather shaped the lives of prehistoric and early humans and also the early representatives of our own species. Possible sources of prehistoric lead contamination could have been contaminated water sources, soil and volcanic eruptions, as the researchers explain.
Brain organoids in the lead stress test
But what were the
Neanderthal Gene Linked to Lead Sensitivity May Have Contributed to Human Advantage
Recent research suggests a genetic difference between modern humans and Neanderthals may explain why Homo sapiens thrived while Neanderthals went extinct – and the key could be lead exposure. A study published in Science Advances (October 16, 2025) reveals that a variant of the NOVA1 gene, present in modern humans but not Neanderthals, appears to offer protection against neurological damage caused by lead.
Researchers at the University of California, san Diego, used brain organoids – miniature, lab-grown human brains – to investigate the effects of lead exposure on different genetic variants. They created organoids with both the modern human NOVA1 gene and the Neanderthal version. The results were striking.
The organoids carrying the Neanderthal gene exhibited important developmental impairments when exposed to lead. Crucially, several vital signaling pathways and genes were disrupted, including FOXP2, a gene critical for speech development. In contrast, the organoids with the modern human NOVA1 variant showed resilience to lead’s damaging effects.
“This suggests that our NOVA1 variant protects us better against neurological damage caused by lead,” explained the research team.
Lead Exposure as a Selective Pressure
The study proposes that lead exposure may have acted as a selective pressure in human evolution. Lead, a pervasive environmental toxin throughout history (from natural sources and later, human activities like smelting), could have disproportionately harmed Neanderthals, hindering their cognitive development and ability to communicate effectively.
“This is an extraordinary example of how an environmental factor – in this case lead toxicity – may have triggered genetic changes that improved survival and our ability to communicate linguistically,” stated senior author Alysson muotri of UC San Diego.
The researchers hypothesize that the protective NOVA1 variant in Homo sapiens allowed our ancestors to maintain better cognitive function and develop more complex language skills, even in the presence of lead. This enhanced interaction ability may have been a crucial factor in their success, ultimately contributing to the extinction of Neanderthals.
Implications for Understanding Human History
This research offers a compelling new perspective on the factors that shaped human evolution. It suggests that our genetic makeup isn’t solely a product of natural selection for beneficial traits, but also a response to environmental challenges like heavy metal toxicity. the findings highlight the complex interplay between genetics, surroundings, and the trajectory of human history.
source: Muotri, A.et al. (2025). Science Advances. doi: 10.1126/sciadv.adr1524