We think of lead poisoning as just damaging, but a new study suggests that periodic lead exposure might have given our ancient ancestors an advantage over Neanderthals.
Researchers analyzed 51 fossilized hominid teeth, which came from early Homo species, great apes, Neanderthals, and early Homo sapiens. All are between 100,000 and 1.8 million years old. In these enamel and dentine layers, they found evidence of lead exposure in 73 percent of the specimens.
Lead exposure is not good for us, but apparently, it was even worse for our Neanderthal cousins. The reason for this lies in a single gene called NOVA1. Modern humans carry a different version of NOVA1 than Neanderthals did. It differs by just a single base pair. The researchers recreated this difference in lab-grown brain cells. Some contained the modern human NOVA1 variant, others the older version that Neanderthals had.
Alysson Muotri with the brain cells. Photo: Erik Jepsen/UC San Diego
Both sets of brains were exposed to levels of lead similar to what they found in the fossilized teeth. Those with the ancient Neanderthal version of NOVA1 all showed less neuron development and more damage to a particular gene that is key to speech and language skills.
This suggests that the modern NOVA1 variant may have protected those parts of the brain responsible for language and communication. These traits are widely believed to contribute to Homo sapiens’ ultimate success.
“These results suggest that our NOVA1 variant may have offered protection against the harmful neurological effects of lead,” says co-author Alysson Muotri. “Language is…our superpower. Because we have language, we are able to organize society and exchange ideas, allowing us to coordinate large movements. There is no evidence that Neanderthals could do that.”
Alysson Muotri. Photo: Kyle Dykes/UC San Diego Health Sciences
Some scientists in this field still have doubts about the researchers’ conclusions. Anthropologist Shara Bailey told Science, “The evidence doesn’t really convince me yet,” since the study does not show that the exposure took place during childhood, when lead exposure would most likely impact brain development.
The study’s researchers emphasize that this is not why Neanderthals went extinct. But it does give insight into how environmental exposure and superior resistance might have affected us.
