Lead is often thought of as a modern toxin, but a new study reveals it has haunted us and our ancestors for nearly 2 million years. Stranger still, the exposure might have given humans an advantage over our closest relatives.
An international team of researchers analyzed the lead content of 51 fossilized hominid teeth, dated between 100,000 and 1.8 million years ago.
The samples came from Homo sapiensthe Neanderthals and some early ones Homo species, as well as more distant relatives like Australopithecus, Paranthropus, Gigantopithecusand fossil species of orangutans and baboons.
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“We found clear signs of episodic lead exposure in 73 percent of specimens (71 percent for hominids). Australopithecus, Paranthropus, And Homo),” the team wrote in its journal.
The dangers of lead exposure are well documented, but the team suggests they could have been even worse for our Neanderthal cousins.
They conducted tests on lab-grown mini-brains that had one of two variants of a gene called NOVA1 – a version that modern humans have and is found in Neanderthals and other extinct species.
Brain organoids carrying the old genetic variant experienced significant disruption in the activity of a gene called FOXP2which codes for a protein essential for speech and language development. Brains carrying the modern variant, however, showed less damage.
“These results suggest that our NOVA1 This variant could have offered protection against the harmful neurological effects of lead,” says Alysson Muotri, a developmental biologist at the University of California, San Diego.
“This is an extraordinary example of how an environmental pressure, in this case lead toxicity, could have driven genetic changes that improved survival and our ability to communicate using language, but now also influence our vulnerability to modern lead exposure.”
Lead toxicity has been linked to a range of serious health problems, such as neurological disorders and cardiovascular disease. This is thought to have harmed mental health and lowered the IQ of entire generations, and even increased crime rates.
This toxicity is generally considered a health problem that largely began with human activity like mining and smelting, and really became widespread around the time of the Industrial Revolution.
Soon we were adding lead to paint and fuel, spreading its toxic influence everywhere.
However, ancient hominids would have been exposed to lead through natural sources, such as volcanic activity, wildfires, and geological processes that increase lead concentrations in food and water sources. And this would have varied depending on the species.
“The teeth of Robust P. consistently showed few low-level lead lines, while A. African And Homo sp. show more frequent exposures,” the researchers write in the new study.
“The different modes of exposure to lead could suggest that Robust P. The lead bands were the result of acute exposure (e.g. wildfires), while for the other two species, known to have a more varied diet, the lead bands may be due to more frequent, seasonal, and higher lead concentration through bioaccumulation processes in the food chain.
While the study doesn’t definitively link our evolutionary success to lead, it paves the way for a possible and intriguing lead into our complicated history with heavy metal.
The research was published in Scientific advances.
