Neanderthals were more susceptible to lead poisoning than humans — which helped us gain an advantage over our cousins, scientists say
Humans and our ancestors have been exposed to lead for nearly 2 million years, researchers have found, overturning the belief that lead poisoning is a relatively modern phenomenon.
Additionally, widespread exposure to this toxic metal may have affected the evolution of our species’ communication abilities. This would have given Homo sapiens a key advantage over our cousins, the Neanderthalswho were more sensitive to the toxic effects of lead, the study suggests.
“Evolution often progresses despite adversity. Stressors like drought, food/water scarcity, or toxins not only threaten survival; they can also lead to the selection of traits that make species more adaptable,” said the study co-author. Renaud Joannès-Boyauprofessor and head of the Geoarchaeology and Archaeometry Research Group (GARG) at Southern Cross University in Australia. “Lead exposure could be one of these hidden forces in our evolutionary history,” he told Live Science in an email.
However, experts noted that the study had limitations because it estimates lead exposure by measuring lead levels in the teeth of many human and related species.
“It is not clear whether the amounts of lead detected in old teeth are actually sufficient to have an impact on health,” said John Hawksanthropologist at the University of Wisconsin-Madison who was not involved in the study. “Measurements of chemicals in tooth enamel have become incredibly sensitive. They may detect such low levels that make no difference,” he told Live Science in an email.
Lead is toxic and high levels of the metal in the body can cause multiple health problems, especially in children, according to the Cleveland Clinic. It can damage the nervous system, especially the brain, as well as other organs, and cause serious learning and behavioral problems.
Today, most lead poisoning is the result of human activities and products, such as painting, mining and smelting, according to the Environmental Protection Agency.
But lead also occurs naturally and can be “found throughout the Earth’s crust, virtually in all rocks, soils, sediments, and waterways in various concentrations,” the researchers write in the study published October 15 in the journal Scientific advances.
“Animals, including humans, can be exposed to substantial levels of lead by drinking contaminated water, ingesting contaminated food, or inhaling polluted air (e.g., smoke from fire and dust storms),” the team added.
Contaminated teeth
In the new study, researchers examined 51 fossilized teeth dating between 1.8 million and 100,000 years ago from a variety of species, including Homo sapiens and our closest relatives, the Neanderthals, as well as relatives such as African Australopithecus And Robust Paranthropusand the monkey disappeared Black Gigantopithecus.
“Teeth form gradually during childhood, so they preserve a detailed record of exposure early in life, the period when the brain is most vulnerable,” Joannes-Boyau said.
The analysis found that 73% of the samples showed “clear signals of episodic lead exposure,” according to the study.. This shows that lead exposure is not a modern phenomenon but rather has impacted human ancestors and their relatives for millions of years.
Exposure levels varied, with some lower than modern industrial levels and others higher, but were generally sufficient to cause impacts on a young, developing brain, Joannes-Boyau noted.
Growing mini brains
Study how lead exposure may have shaped the development of Homo sapiensresearchers created two different versions of the brain “organoids” — miniature, simplified models of life-size human brains.
Each organoid version had different variants of the NOVA1 gene. Modern humans have a unique version of this gene that is important for brain development and has also been linked to language skills. Neanderthals and other human relatives have a slightly different version of this gene.
When exposed to lead, the organoid with the modern NOVA1 gene showed greater resistance to the toxic metal than the organoid with the archaic variant. In particular, the Homo sapiens The NOVA1 version appears to help maintain the activity of a gene called FOXP2, which plays a crucial role in human speech and language development.
“When the brain is exposed to stressors like lead, the modern NOVA1 variant helps maintain stable FOXP2 function, protecting pathways related to speech, communication and cognition,” Joannes-Boyau said.
In contrast, in the brain organoid with the archaic variant of NOVA1, FOXP2 expression was altered when exposed to lead.
Co-author of the study Alysson Muotridirector of the Center for Stem Cell Education and Integrated Orbital Space Stem Cell Research at the University of California San Diego Sanford, noted that this could have given humans an evolutionary advantage.
“Most likely, the modern NOVA1 variant arose after exposure to lead, but was quickly selected for because it gave us an advantage over other hominids,” such as Neanderthals, he said in an email to Live Science. “This is another example of evolution in action.”
But the data on the NOVA1 gene are subject to interpretation, Debbie Guatelli-Steinbergprofessor in the department of anthropology at Ohio State University, told Live Science in an email.
“The authors argue that the human NOVA1 variant gave humans a competitive advantage over other hominids, including Neanderthals,” Guatelli-Steinberg said. “This idea is speculative.”
Hawks said the study raises questions about how these ancient human ancestors and their relatives were exposed to lead. “Did they absorb lead when they used shiny minerals as pigments?” “Did they absorb it in the pollutants from the burns? Or in the plant foods they ate? These are open questions. I’d like to know the answers.”
Neanderthal Quiz: What do you know about our closest relatives?
