A new study revealed that human ancestors were exposed to lead millions of years ago, which may have influenced the evolution of our brain.
By Renaud Joannes-Boyau, Alysson R. Muotri and Manish Arora
United Kingdom, October 19 (The Conversation).- When we think about poisoning by lead, most of us imagine the pollution modern caused by man, paint, old pipes or exhaust gases.
But a new study published in Science Advancesreveals something much more surprising: our forefathers were exposed to lead for millions of years, and may have helped shape the evolution of the human brain.
This discovery reveals that the toxic substance we fight against today has been intertwined with the history of human evolution since its beginning.
It reshapes our understanding of both the past and the present, drawing a continuous thread between ancient environments, genetic adaptation, and the developing evolution of human intelligence.
A poison older than humanity itself
Lead is a powerful neurotoxin that disrupts the growth and function of both the brain and body. There is no safe level of lead exposure, and even the smallest traces can affect memory, learning, and behavior, especially in children. That’s why removing lead from gasoline, paint, and plumbing is one of the most important public health initiatives.
Hominids experienced lead exposure as far back as 2 million years ago, new research finds, challenging the theory that the neurotoxicant is an exclusively modern health hazard. pic.twitter.com/stEEwl7zJ3
— Science Advances (@ScienceAdvances) October 16, 2025
However, when analyzing ancient teeth at Southern Cross University, researchers discovered something totally unexpected: clear traces of lead sealed within the fossils of early humans and other ancient species.
These specimens, recovered from Africa, Asia and Europe, were up to two million years old.
Using lasers thinner than a strand of hair, each tooth was scanned layer by layer, like reading the growth rings of a tree. Each band recorded a brief chapter of the individual’s life. When lead entered the body, it left a vivid chemical signature.
These signatures revealed that the exposure was neither rare nor accidental; occurred repeatedly over time.
Where did this clue come from?
The findings show that early humans were never protected from lead by the natural world. On the contrary, it was also part of his world.

The lead found did not come from mining or smelting; those activities are from relatively recent human history.
Instead, it probably came from natural sources such as volcanic dust, mineral-rich soils, and groundwater flowing through lead-bearing rocks in caves. During times of drought or food scarcity, early humans may have dug for water or eaten plants and roots that absorbed lead from the soil.
Each fossil tooth studied is a record of survival. A small diary of the individual’s early life, written in minerals rather than words. These ancient traces tell us that even as our ancestors struggled to find food, shelter, and community, they also navigated a world full of unseen dangers.
From fossil teeth to living brain cells
To understand how this ancient exposure might have affected brain development, researchers teamed up with geneticists and neuroscientists, and used stem cells to grow small versions of human brain tissue, called brain organoids. These small collections of cells have many of the characteristics of developing human brain tissue.
The scientists gave some of these organoids a modern human version of a gene called NOVA1, and others an archaic, extinct version of the gene similar to that carried by Neanderthals and Denisovans. NOVA1 is a gene that orchestrates early neurodevelopment. It also initiates the response of brain cells to major pollutants.


Both sets of organoids were then exposed to very small, realistic amounts of lead, which ancient humans might have encountered naturally.
The difference was surprising. The organoids with the old gene showed clear signs of stress. Neural connections were not formed as efficiently and key pathways related to communication and social behavior were disrupted. Modern gene organoids, however, were much more resilient.
It seems that, at some point along the evolutionary path, our species may have developed better built-in protection against the harmful effects of lead.
A story of struggle
The environment, with lead exposure, pushed modern human populations to adapt. People with genetic variations that help them resist a threat are more likely to survive and pass those traits on to future generations.
In this way, lead exposure may have been one of the many invisible forces that sculpted human history. By favoring genes that fortified our brains against environmental stress, it could have subtly shaped the way our neural networks developed, influencing everything from cognition to the earliest roots of speech and social connection.


This did not change the fact that lead is still a toxic chemical. It remains one of the most harmful substances for our brain.
But evolution often works through struggle; even negative experiences can leave lasting, sometimes beneficial, marks on our species.
New context for a modern problem
Understanding our long relationship with lead gives new context to a very modern problem. Despite decades of bans and regulations, lead poisoning remains a global health problem. UNICEF’s most recent estimates show that one in three children worldwide still have blood lead levels high enough to cause harm.
Our discovery shows that human biology evolved in a world full of chemical challenges. What changed is not the presence of toxic substances, but the intensity of our exposure.
When we look at the past through the lens of science, we don’t just discover old bones, we discover ourselves.
In the industrial age, we have massively amplified what used to be a short and infrequent natural exposure. By studying how our ancestors’ bodies and genes responded to environmental stress, we can learn how to build a healthier, more resilient future.
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