Prehistoric encounters with lead may have influenced the wiring of the human brain and helped Homo sapiens outpace their archaic cousins, according to a new publictaion in Science Advances. The researchers combined chemical analysis of fossils with experiments on laboratory-grown brain organoids to test whether a single mutation in the NOVA1 gene reduced the metal’s impact.
The group laser-scanned 51 fossilised teeth from Africa, Europe, and Asia, dating from 1.8 million to 100,000 years ago. The sample included Australopithecus africanus, Homo neanderthalensis, early Homo sapiens, and Gigantopithecus blacki. Lead bands appeared in 73 percent of the specimens, and several reached more than 50 parts per million.
“I was especially surprised by the amount of lead in Gigantopithecus blacki, which showed the most frequent acute exposure,” said Renaud Joannes-Boyau, a geochemist at Southern Cross University, according to Science Daily. The team attributed the contamination to natural sources such as volcanic eruptions, wildfires, and polluted soil and water.
To explore evolutionary effects, the scientists grew two sets of brain organoids—one carrying the modern NOVA1 variant and the other the Neanderthal-like version—then exposed them to small doses of lead. “Following lead exposure, organoids carrying the archaic NOVA1 variant exhibited disruptions to FOXP2 activity in neurons associated with speech and language development, while those with the modern variant were far less affected,” wrote Alysson Muotri’s group at the University of California, San Diego. “It’s an extraordinary example of how an environmental pressure, in this case lead toxicity, could have driven genetic changes that improved survival and our ability to communicate using language,” said Muotri, according to ABC News Australia.
Because the modern NOVA1 gene differs from the Neanderthal form by a single DNA base pair, the authors argued that the mutation likely faced strong selection in Homo sapiens, providing neural protection and possibly encouraging more complex language and social cohesion.
Skepticism remained. “This is a really complex paper that makes some highly speculative claims,” said Tanya Smith, a biological anthropologist at Griffith University, to Smithsonian Magazine. Shara Bailey of New York University offered similar reservations, while Yassine Souilmi of the Australian Centre for Ancient DNA called the proposed link “tenuous and based mainly on circumstantial evidence,” noting that organoids cannot fully replicate evolutionary processes.
Comparable lead patterns turned up in the teeth of 12 people born between the 1940s and 1970s, when leaded gasoline and paint were common. “We thought lead was only a modern experience of humans,” said Joannes-Boyau, according to ABC News Australia. “We found the opposite.”
Lead still harms developing brains. The World Health Organization linked the metal to more than 1.5 million deaths in 2021, and it continues to leach from car batteries, ceramics, cosmetics, and aging water pipes. “Our work not only rewrites the history of lead exposure,” said Joannes-Boyau in Izvestia, “it also reminds us that the interaction between our genes and the environment has been shaping our species for millions of years, and continues to do so.”
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