Long considered a modern form of pollution linked to human activity, lead exposure actually predates the Iron Age. A new study shows that hominid fossils, which include the human lineage and primates, have been exposed to lead for at least 2 million years.
Lead is a heavy metal with no biological role. It accumulates in the body and disrupts red blood cell production, the nervous system and the kidneys, with particularly serious effects in children. Until now, it was thought that this exposure was entirely linked to human activities, appearing with metallurgy in ancient times and amplified by industrialisation.
Lead, an old companion of humankind
By analysing the fossilised teeth of 51 hominids – from primates to the human lineage and Australopithecus – Australian researchers have discovered biogenic traces of lead dating back two million years. Some levels exceed those observed at the height of industrial pollution, as explained by Renaud Joannes-Boyau, co-author of the study published in Science Advances: ‘We see levels that are, even occasionally, much higher than during the peak industrial period, i.e. the 1950s and 1960s.’ Exposure to lead is therefore not unique to modern humans, but was already part of the primate environment. Scientists have also identified a genetic variant specific to Homo sapiens that limits the neurological effects of lead, unlike Neanderthals or Denisovans. Listen to the entire episode to understand why this discovery is the result of a happy coincidence.
