How a sliver of DNA helped build the human capacity for language
Scientists have discovered tiny pieces of DNA that play a big role in human language. These ancient traits existed before Neanderthals and stayed largely unchanged due to limits linked to brain growth and childbirth.
In a new study published in the journal Science Advances, researchers from the University of Iowa Health Care reveal that genetic sequences would have impacted humans’ language abilities and the sequences would have evolved before humans and Neanderthals diverged.
The senior authors describe language as a defining trait of Homo sapiens, as other animals communicate in different ways, and humans as the only species able to develop and improvise language, which is unique to our species. The study aimed to understand how the development of human language was shaped by genetic regulatory sequences called Human Ancestor Quickly Evolved Regions (HAQERs).
“What we’re seeing is how a very small part of the genome can have an outsized influence, not just on who we were as a species, but on who we are as individuals,” Michaelson said, noting that HAQERs represent less than a tenth of a per cent of the genome but drive roughly 200 times more impact on language ability than any other genomic region. These parts of the genome are instructions for building the ‘hardware’ of the brain, and language is the ‘software’.
Foundations of the study were completed two decades ago
The foundations of the study were completed in the 1990s by Bruce Tomblin, a professor emeritus of the UI Department of Communication Sciences and Disorders. He studied 350 Iowa students to try to better understand language abilities by documenting their abilities and collecting saliva to preserve it for future DNA sequencing. The process was completed thanks to funded research that analysed differences in DNA and how gene variations affected students’ language skills. Through this, they could analyse the broader impact of HAQERs on an individual's ability to communicate using language.
“These aren't genes we're talking about. They're regulatory regions that act like the volume knob on genes,” Michaelson explained, adding that the finding connected with a study from 20 years ago, which identified the FOXP2 gene, a transcription factor, which was thought to play a role in language impairment. “So, if the HAQERs are like volume knobs that can be turned, FOXP2 is one of the hands that is turning these volume knobs.”
To understand the impact of HAQERs, the team developed an evolutionary-stratified polygenic score (ES-PGS) that divides genetic effects by evolutionary origin. Using computational genetics, the team looked at 65 million years of history.
These ‘volume knobs’ were seen in Neanderthals and could have been more prominent than they are in modern humans. The findings reveal that HAQERS are ancient innovations that shape language, even though Neanderthals' overall cognitive abilities were probably very different from those of modern-day humans.
“This HAQERs aspect, a sliver of the genome, has remained relatively constant, even as other aspects have been going up and up and up to make modern humans smarter and smarter,” Michaelson said. "We can say humans at least had the ‘hardware’ for language earlier than what we previously thought.”
Michaelson also added that archaeological evidence of Neanderthals also showed they had culture and organised social structures, implying they would have used a form of complex communication. However, this raises the question of if HAQERs are beneficial to language; why have they not evolved into new gene variants?
The answer: Balancing selection. In this study, HAQERs’ genetic signals plateaued, whereas signals for cognitive abilities continued to change as modern humans evolved. The team suggests that HAQERs promote fetal brain development, potentially increasing brain and skull size. Before now, there was a limit for how large a baby’s head could become before delivery would be dangerous for the child and mother, increasing mortality.
“We think that early humans maxed out this pathway to developing the kind of brain that could be a vessel for language and they hit that ceiling pretty early on and then remained stable, while other aspects of genetics that improve brain development for higher intelligence but don’t directly affect fetal brain size, continued to evolve,” Michaelson said.
Therefore, humans faced an evolutionary trade-off: the ‘hardware’ for language could not be optimised further without an increased mortality rate among infants and mothers.
Potential future research
Michaelson's laboratory wished to further the research with additional studies involving the students analysed by Tomblin. The original study was completed 30 years ago, and some individuals may now have families of their own, offering a large sample for the genetic research.
“One of the things we're interested in is disentangling the environmental input from the genetic input, when thinking about how a child masters language,” Michaelson said, noting that children raised in a linguistically rich environment may present higher language capabilities. “Using that family structure, we hope to separate the direct genetic effects on language and what researchers call ‘genetic nurture’ where the parents’ genetics influence the environment they create for their kids.”
News reference:
Ancient regulatory evolution shapes individual language abilities in present-day humans | Science Advances. Casten, L.G., Koomar, T., Thomas, T.R., Koh, J.-Y., Hofammann, D., Thenuwara, S., Momany, A., O’Brien, M., Murray, J.C., Tomblin, J.B. and Michaelson, J.J. 22nd April 2026.