Ancient human relatives were exposed to lead up to two million years ago, according to a new study. However, a gene mutation may have protected modern human brains, allowing language to flourish.
Lead banding in fossilized teeth of several hominid species during the Pleistocene. Blue indicates no lead exposure during tooth formation; red indicates high exposure. Photo credit: UC San Diego Health Sciences.
They detected lead in 73% of the specimens, including 71% of modern and archaic humans. Notably, G. blacki fossils dating back 1.8 million years showed the most frequent acute lead exposure. It’s long been assumed that humans have been exposed to harmful amounts of lead since antiquity — when the Romans used lead pipes to transport water — and that lead contamination increased significantly during the Industrial Revolution, only to be curtailed during the late twentieth century.
Did Lead Limit Brain and Language Development in Neanderthals and Other Extinct Hominids? Ancient human relatives were exposed to lead up to two million years ago, according to a new study. However, a gene mutation may have protected modern human brains, allowing language to flourish. UC San Diego researchers have found high levels of lead in the teeth of both Neanderthals (left) and modern humans (right). However, a gene mutation may have protected modern human brains, allowing language to flourish. Photo credit: Kyle Dykes/UC San Diego Health Sciences
“We stopped using lead in our daily lives when we realized how toxic it is, but nobody had ever studied lead in prehistory,” said corresponding author Alysson Muotri, Ph.D., professor of pediatrics and cellular & molecular medicine at UC San Diego School of Medicine, associate director of the Archealization Center and director of the Sanford Integrated Space Stem Cell Orbital Research Center. Surprisingly, teeth from people born between the 1940s and 1970s — when children were exposed to leaded gasoline and paint — showed similar patterns of lead exposure to fossilized human teeth. The team hypothesizes that, like the Romans, ancient humans and other hominids may have been exposed to lead because of their need for water. “One possibility is that they were looking for caves with running water inside,” Muotri said. “Caves contain lead, so they were all contaminated. Based on the tooth enamel studies, it started very early in infancy.” Lead exposure impedes brain development, leading to deficits in intelligence and difficulties with emotional regulation. Alysson Muotri, Ph.D. Photo credit: Kyle Dykes/UC San Diego Health Sciences
Given these findings, Muotri and his team wondered how the modern human brain had flourished despite exposure to lead during our evolution. A tiny genetic change A gene called neuro-oncological ventral antigen 1 (NOVA1) plays a central role in human brain development and synapse formation. Considered the master regulator of neurodevelopment, NOVA1 controls how neural progenitor cells respond to lead. Disruption of NOVA1 activity is linked to several neurological disorders. Most modern humans have a variant of NOVA1 gene that differs by a single DNA base pair from the ancestral version that was present in Neanderthals. Previous work by Muotri and his colleagues showed that replacing the human NOVA1 variant with the archaic variant resulted in significant changes to the architecture and synaptic connectivity of tiny stem-cell-derived models of human brains called organoids. The researchers hypothesize that ancient hominids were exposed to lead in caves. Photo credit: iStock
Lead exposure altered NOVA1 expression in both variants, affecting genes linked to neurodevelopmental disorders such as autism and epilepsy. However, only the archaic NOVA1 variant changed the expression of FOXP2, a gene essential for language and speech development. People with certain FOXP2 mutations cannot produce sophisticated language. “ These type of neurons related to complex language are susceptible to death in the archaic version of NOVA1,” said Muotri. “ The FOXP2 gene is identical between us and the Neanderthals, but it’s how the gene is regulated by NOVA1 that likely contributes to language differences.” Evolutionary implications 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, Ph.D.
The findings suggest that the acquisition of the modern NOVA1 variant may have protected us from the detrimental effects of lead, promoting complex language development and social cohesion. This could have given modern humans a significant evolutionary advantage over Neanderthals, even in the presence of lead contamination. Muotri believes these results have important implications for understanding how environmental stressors shaped brain development during human evolution. He speculates that lead exposure may have contributed to the extinction of Neanderthals around 40,000 years ago. “Language is such an important advantage, it’s transformational, it is our superpower,” said Muotri. “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. They might have had abstract thinking, but they could not translate that to each other. And maybe the reason is because they never had a system to communicate that was as efficient as our complex language.”
The study’s co-authors included Janaina Sena de Souza, Sandra M. Sanchez-Sanchez, Jose Oviedo, University of California San Diego; Marian Bailey and Matthew Tonge at Southern Cross University; Renaud Joannes-Boyau, Southern Cross University and University of Johannesburg; Justin W. Adams, University of Johannesburg and Monash University; Christine Austin, Manish Arora, Icahn School of Medicine at Mount Sinai, Kira Westaway, Macquarie University; Ian Moffat, Flinders University and University of Cambridge; Wei Wang and Wei Liao, Anthropology Museum of Guangxi; Yingqi Zhang, Institute of Vertebrate Paleontology and Paleoanthropology; Luca Fiorenza, Monash University and Johann Wolfgang Goethe University; Marie-Helene Moncel, Museum National d’Histoire Naturelle; Gary T. Schwartz, Arizona State University; Luiz Pedro Petroski and Roberto H. Herai, Pontifícia Universidade Católica do Paraná; Jose Oviedo, University of Arizona; and Bernardo Lemos, Harvard T. H. Chan School of Public Health. The study was funded, in part, by the National Institutes of Health (grants R01 ES027981, P30ES023515, R01ES026033), the Australian Research Council (grant DP170101597), the National Science Foundation (grant BCS 0962564), and the The Leakey Foundation. Alysson Muotri, Ph.D. with brain organoids. Photo by Erik Jepsen/UC San Diego
“We stopped using lead in our daily lives when we realized how toxic it is, but nobody had ever studied lead in prehistory,” said corresponding author Alysson Muotri, Ph.D., professor of pediatrics and cellular & molecular medicine at UC San Diego School of Medicine, associate director of the Archealization Center and director of the Sanford Integrated Space Stem Cell Orbital Research Center.
Surprisingly, teeth from people born between the 1940s and 1970s — when children were exposed to leaded gasoline and paint — showed similar patterns of lead exposure to fossilized human teeth.
The team hypothesizes that, like the Romans, ancient humans and other hominids may have been exposed to lead because of their need for water.
“One possibility is that they were looking for caves with running water inside,” Muotri said. “Caves contain lead, so they were all contaminated. Based on the tooth enamel studies, it started very early in infancy.”
Lead exposure impedes brain development, leading to deficits in intelligence and difficulties with emotional regulation.
Given these findings, Muotri and his team wondered how the modern human brain had flourished despite exposure to lead during our evolution.
A gene called neuro-oncological ventral antigen 1 (NOVA1) plays a central role in human brain development and synapse formation. Considered the master regulator of neurodevelopment, NOVA1 controls how neural progenitor cells respond to lead. Disruption of NOVA1 activity is linked to several neurological disorders.
Most modern humans have a variant of NOVA1 gene that differs by a single DNA base pair from the ancestral version that was present in Neanderthals. Previous work by Muotri and his colleagues showed that replacing the human NOVA1 variant with the archaic variant resulted in significant changes to the architecture and synaptic connectivity of tiny stem-cell-derived models of human brains called organoids.
Lead exposure altered NOVA1 expression in both variants, affecting genes linked to neurodevelopmental disorders such as autism and epilepsy.
However, only the archaic NOVA1 variant changed the expression of FOXP2, a gene essential for language and speech development. People with certain FOXP2 mutations cannot produce sophisticated language.
“ These type of neurons related to complex language are susceptible to death in the archaic version of NOVA1,” said Muotri. “ The FOXP2 gene is identical between us and the Neanderthals, but it’s how the gene is regulated by NOVA1 that likely contributes to language differences.”
The findings suggest that the acquisition of the modern NOVA1 variant may have protected us from the detrimental effects of lead, promoting complex language development and social cohesion. This could have given modern humans a significant evolutionary advantage over Neanderthals, even in the presence of lead contamination.
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