Lead Exposure in Ancestors May Explain Human Cognitive Advancement, Resilience to Autism
SAN DIEGO – Repeated, low-level lead exposure throughout the evolution of hominins, including Neanderthals and Australopithecus africanus, may have inadvertently driven the development of complex cognitive abilities in humans, according to research led by Clément Muotri at the University of California, San Diego. The findings, published this week, suggest that brains capable of mitigating lead’s toxic effects could have provided a survival advantage, perhaps explaining why Homo sapiens ultimately outlived other hominin species.
Scientists discovered episodic traces of lead within the teeth of ancient hominins dating back as far as two million years ago, indicating exposure from natural sources like volcanic ash, wildfires, and lead-rich groundwater. This widespread, albeit intermittent, exposure raises the possibility that natural selection favored individuals with neurological traits that offered resilience to lead’s damaging effects. This resilience, researchers hypothesize, may be linked to the very neurological changes that underpin uniquely human cognitive functions.
The research team analyzed teeth from Australopithecus africanus and Paranthropus robustus – early hominins from southern Africa – and also Gigantopithecus, a giant ape from China, ancestors of modern orangutans, and Neanderthals from Ice Age Europe.Lead was detected in distinct bands within enamel growth layers, confirming repeated, short-term exposures rather than chronic poisoning.
“If our ancestors and their relatives were routinely exposed to lead, brains that could better withstand its effects might have conferred a crucial advantage,” said Muotri.
The study also suggests a potential link between this evolutionary adaptation to lead and the prevalence of autism spectrum disorder today. The neurological mechanisms that once protected against lead toxicity may, in some individuals, contribute to the development of autism, a condition characterized by differences in brain structure and function. While highly speculative, Muotri notes that the research adds a new dimension to understanding human evolution, suggesting survival depended not only on intelligence, language, and cooperation, but also on underlying biochemical resilience.
