Lead Exposure May Have Influenced Human Evolution

LISMORE, AUSTRALIA—An international team of scientists suggests that human ancestors were periodically exposed to lead over two million years of evolution, according to a statement released by Southern Cross University. Led by Renaud Joannes-Boyau of Southern Cross University and Janaina Sena de Souza of the University of California San Diego, the researchers analyzed teeth from Australopithecus africanus, Paranthropus robustus, early Homo species, Neanderthals, and modern humans with high-precision laser-ablation geochemistry. The testing detected repeated bands of lead in the teeth, which had been formed during childhood. The scientists think that young hominins were likely to have been exposed to the toxic metal through contaminated water, soil, or volcanic activity. To test the idea that this exposure might have influenced the development of hominin brains, the scientists used human brain organoids, which are miniature model brains grown in the lab, to test the effect of lead on NOVA1, a developmental gene known to differ between modern humans and extinct hominids, and to be affected by exposure to lead. When organoids carrying the extinct NOVA1 variant were exposed to lead, development of regions of the brain critical for speech and language were disrupted. Yet organoids carrying the modern human version of NOVA1 were not affected as severely. “These results suggest that our NOVA1 variant may have offered protection against the harmful neurological effects of lead,” said team member Alysson Muotri of the University of California San Diego, perhaps resulting in an evolutionary advantage for modern humans. Read the researchers' scholarly paper in Science Advances. To read about research into Neanderthal brain development, go to "Neanderthal Brain Strain."