A new study has uncovered that lead exposure has been a significant factor in human evolution, challenging the belief that such exposure is primarily a modern issue linked to industrial activities. Conducted by a collaborative international team, this research reveals that our ancestors encountered lead for over two million years, potentially impacting brain development, behavior, and even language.
The research, led by scientists from the Southern Cross University in Australia, the Mount Sinai Hospital in New York, and the University of California, San Diego, utilized fossilized teeth to explore ancient lead exposure. This groundbreaking study, published in Science Advances, indicates that lead, a toxic metal, has been part of the human environment for millennia, shaping cognitive and social behaviors among early hominins.
Through the analysis of 51 fossilized teeth from various hominid species, such as Australopithecus africanus, Paranthropus robustus, and Homo sapiens, researchers identified distinct chemical signatures indicative of intermittent lead exposure dating back nearly two million years. These findings suggest that lead absorption occurred not just from environmental sources, like contaminated water and soil, but also from bodily reserves during times of stress or illness.
Professor Renaud Joannes-Boyau, head of the research group at Southern Cross University, emphasized that this study illustrates how environmental pressures have been integral to human evolution. “Our data indicate that lead exposure was not merely a product of the Industrial Revolution; it has been woven into our evolutionary tapestry,” he stated. “This suggests that the brains of our ancestors developed under the influence of this potent toxin, possibly affecting their social behaviors and cognitive capabilities over time.”
Additionally, the team investigated how ancient lead exposure could have influenced brain development by utilizing human brain organoids—miniature brain models grown in the lab. They compared the effects of lead exposure on organoids carrying two variants of a crucial developmental gene, NOVA1. The modern version of this gene differs from its archaic counterparts found in Neanderthals and other extinct hominids.
By exposing organoids with the archaic variant of NOVA1 to lead, significant alterations in the activity of FOXP2, a gene essential for speech and language development, were observed. This impact was less pronounced in organoids with the modern variant, suggesting that the contemporary version may provide some protection against the neurotoxic effects of lead.
Professor Alysson Muotri from UC San Diego noted that this research exemplifies how environmental factors, like lead toxicity, could have driven genetic changes that enhanced our survival and communication abilities. “This legacy of vulnerability to lead exposure is an inherited trait from our evolutionary past,” he remarked.
Despite the modern context of lead exposure being largely due to human activities, it remains a pressing global health issue, particularly for children. These findings underscore the intricate relationship between environmental toxins and human biology, highlighting that our susceptibility to lead may be rooted in a long history of interaction with this toxic element.
