Could Lead Have Shaped the Evolution of the Human Brain?
A recent study published in Science Advances has turned a long-held assumption on its head. According to the research, humans and their ancestors were exposed to lead almost two million years ago, and this toxic metal may have played an unexpected role in shaping the evolution of our brains and even our ability to speak.
An international research team led by the University of California San Diego and Southern Cross University examined 51 fossilised teeth from Homo sapiens, Neanderthals, and extinct apes such as Gigantopithecus blacki. These fossils, dated between 100,000 and 1.8 million years old, were discovered across Africa, Asia, and Europe.
Using advanced laser-ablation techniques, the scientists detected traces of lead in around 73 per cent of the samples, clear evidence that our ancient relatives were chronically exposed to the metal long before modern industry existed.
Photo Credit: Joannes-Boyau, R., de Souza, J. S., Arora, M., Austin, C., Westaway, K., Moffat, I., … Muotri, A. R. (2025)
Unlike the pollution we associate with petrol and factories today, prehistoric lead contamination had natural origins. It likely came from volcanic ash, mineral-rich cave water, and soil. This discovery challenges the idea that lead poisoning is a purely modern phenomenon.
Lead is notoriously harmful, especially to developing brains. Even small doses can damage cognition and communication, two abilities vital for survival and cooperation. So how did Homo sapiens manage to thrive in such toxic conditions, while Neanderthals and other close relatives eventually vanished?
The clue may lie in a single gene known as NOVA1, which helps regulate brain development and neural communication. Modern humans carry a slightly different version of this gene compared with Neanderthals, a change of just one DNA base pair, yet one that might have made all the difference.
To explore this, the researchers grew miniature brain “organoids” in the lab, each carrying either the modern human or the Neanderthal version of NOVA1. When the organoids were exposed to lead, the difference was striking. Those with the modern human gene were far more resilient, maintaining healthy brain cell growth. In contrast, the Neanderthal variant disrupted another crucial gene called FOXP2, which is essential for speech and language.
This suggests that the human-specific NOVA1 mutation could have shielded our ancestors’ brains from environmental toxins, and, in doing so, may have supported the evolution of language and complex communication.
If this theory is correct, it could explain why Homo sapiens eventually outcompeted Neanderthals. The ability to communicate more effectively would have fostered stronger social bonds, cooperation, and cultural exchange, all traits that gave our species a critical edge in adapting to new environments and spreading across the planet.
The researchers are quick to note that their conclusions remain speculative. While the chemical and experimental evidence is compelling, there’s no direct genetic data from ancient fossils to confirm the hypothesis.
Even so, the idea is fascinating: that a toxic element once thought to threaten our survival might, paradoxically, have helped forge the very traits that make us human.