Ancient Lead Exposure Could Have Shaped Brain Evolution

Research on fossilized teeth indicates that ancient humans were exposed to harmful lead for over two million years, suggesting that modern humans might have adapted to handle this toxic metal more effectively than their predecessors.

Traditionally, lead poisoning was associated with modern issues such as industrialization, poor mining techniques, and lead additives in fuels. Fortunately, efforts to phase out lead exposure have been underway since the 1980s.

This toxin is particularly harmful to children, hindering physical and cognitive growth, while adults may experience a range of serious physical and mental health issues.

Dr. Renaud Joanne Bois and colleagues from Southern Cross University in Lismore, Australia, aimed to investigate whether our ancient ancestors faced similar lead exposure.

They examined 51 fossilized hominin teeth, representing species such as Australopithecus africanus, Paranthropus robustus, Gigantopithecus black, Homo neanderthalensis, and Homo sapiens. The fossils were sourced from regions including Australia, Southeast Asia, China, South Africa, and France.

The research team utilized laser ablation techniques to identify lead concentrations in the teeth, revealing layers of lead that accumulated during the growth of these hominids. This exposure could be attributed to environmental contaminants, such as polluted water, soil, or volcanic eruptions.

Dr. Joanne Boyau noted the surprising levels of lead discovered within the teeth. For instance, Gigantopithecus, a massive ancestral relative of today’s orangutans, primarily lived in what is now China. “If current humans exhibit similar lead levels, it indicates considerable exposure from industrial activities,” she remarked.

The research then shifted focus to understanding how both modern humans and Neanderthals managed lead exposure. The team created lab-grown brain models called organoids to analyze differences in the NOVA1 gene in both species, subsequently assessing the effects of lead neurotoxicity on these organoids.

“Our findings indicate that modern NOVA1 is significantly less impacted by lead neurotoxicity,” states Joannes Boyau.

Crucially, when archaic organoids expressed NOVA1 under lead exposure, another gene, Fox P2 exhibited notable differences.

“These genes are linked to cognitive functions, language, and social bonding,” explains Joannes-Boyau. “The diminished neurotoxicity in modern humans compared to Neanderthals could provide a crucial evolutionary advantage.” This suggests that lead exposure has influenced our evolutionary history.

However, Dr. Tanya Smith from Griffith University in Brisbane, Australia, remains cautious about the conclusions drawn by the researchers regarding lead exposure levels or potential evolutionary benefits inferred from their organoid studies.

“This paper is complex and makes speculative claims,” Smith emphasizes. “While it seems logical that ancient humans and wild primates faced some level of lead exposure, the limited scope and variety of fossils studied do not necessarily demonstrate that our ancestors were consistently exposed to lead over two million years.”

Exploring Neanderthals and Ancient Humans in France

Join New Scientist’s Kate Douglas on an engaging exploration of significant Neanderthal and Upper Paleolithic sites across southern France, spanning from Bordeaux to Montpellier.