A newly published study from the University of Iowa Health Care shows that a surprisingly small part of human DNA plays a major role in language ability. The researchers also found that these impressive genetic sequences emerged before modern humans and Neanderthals diverged from a common ancestor, pushing the origins of language-related biology further back in time than previously recognized.
Jacob Michelson, PhD, UI Roy J. And Lucille A. Roy J., professor of psychiatry and neuroscience at Carver College of Medicine. Carver says language is one of the defining characteristics of Homo sapiens. Many animals communicate, but humans have the extraordinary ability to create, adapt, and expand language in ways unmatched by other species.
Michelsen and his colleagues, including first author Lucas Kasten, PhD, now a postdoctoral researcher at the Max Planck Institute of Psychiatry in Munich, Germany, worked to investigate how the development of human language may be influenced by genetic regulatory elements known as human ancestral accelerated evolving regions (HAQERs).
“What we’re seeing is that a very small part of the genome can have an outsized impact, not only on who we were as a species, but also on who we are as an individual,” says Michelson, noting that HAQER represents less than one-tenth of one percent of the genome, but has about 200 times more influence on language ability than any other genomic region.
According to the researchers, these DNA regions help form the biological “hardware” of the brain, while language itself serves as the “software.”
Ancient DNA and the Origins of Language
Conclusion, published in science advancementBased on research begun in the 1990s. At that time, Bruce Tomblin, PhD, now professor emeritus in the UI Department of Communication Sciences and Disorders, studied the language abilities of 350 students in Iowa.
Tomblin carefully documented each student’s language skills and collected saliva samples, preserving DNA that could be analyzed in the future. Years later, Michelson’s laboratory completed genetic sequencing through NIH-funded research, making it possible to examine how differences in DNA relate to variation in language ability.
As researchers explored the data, they became interested in HAQER’s broader role in human communication.
“These are not genes we’re talking about. They’re regulatory regions that act like volume knobs on genes,” Michaelson explains, linking the findings to a seminal study from 20 years ago that identified the FOXP2 gene, a transcription factor that was initially suspected to play a major role in language impairment. “So, if HAQER are like volume knobs that can be turned, then FOXP2 is one of the hands that is turning these volume knobs.”
To better measure the impact of HAQERs, the researchers created an evolutionary-stratified polygenic score (ES-PGS), a tool that differentiates genetic effects according to how they emerged during evolution. Using computational genetics, the team traced genetic influences across nearly 65 million years of evolutionary history.
Shared genetic characteristics with Neanderthals
The analysis revealed that these genetic “volume knobs” were already present in Neanderthals and may have been slightly more pronounced than in modern humans.
For researchers, this was a particularly important discovery because it suggests that there are ancient biological innovations associated with the HAQER language. This relationship exists despite the possibility that Neanderthals differed significantly from modern humans in many aspects of cognition.
“This HAQERs aspect, one piece of the genome, has remained relatively stable, even as other aspects are going up and up to make modern humans smarter,” Michelson says. “We can say that humans at least had the ‘hardware’ for language earlier than we previously thought.”
Michelson says archaeological evidence already shows that Neanderthals had culture, social organization, and complex behavior. When combined with new genetic findings, those observations strongly suggest that some form of sophisticated communication may have existed long before modern humans appeared.
The results also raise an important question. If HAQER are so beneficial to the language, why did they stop changing instead of continuing to evolve?
an evolutionary tradeoff
Researchers believe the answer involves a process known as balancing selection.
While genetic signatures associated with other cognitive abilities continued to evolve, the influence of HAQERs appears to have reached a plateau. According to the team, these genetic regions aid in fetal brain development in a way that also increases the size of the brain and skull.
However, before modern medicine, there were limits to how big a baby’s head could grow before childbirth became dangerously difficult for both mother and baby. Large head size can significantly increase the risk of mortality during delivery.
Michelson says, “We believe that early humans maximized this pathway to developing the kind of brain that could be a conduit for language and that they reached that limit very early and then remained stable, while other aspects of genetics that improve brain development for higher intelligence but do not directly affect fetal brain size continued to evolve.”
In other words, human evolution may have reached a point where further improvements in the biological “hardware” supporting language would come at too great a cost to maternal and infant survival.
separating genetics from environment
The team plans to continue exploring these questions using the same group of participants originally studied by Tomblin.
Since that research began nearly three decades ago, many of those participants now have children and families of their own. This creates a valuable opportunity to examine how language ability is shaped by both inherited genetics and environmental influences.
“One of the things we’re interested in is separating environmental input from genetic input when we think about how a child masters language,” Michaelson says, noting that children raised in linguistically rich environments may present with higher language abilities. “Using that family structure, we hope to isolate direct genetic influences on language and what researchers call ‘genetic nurture,’ where parents’ genetics influence the environment they create for their children.”
Michelson says the University of Iowa has advanced statistical tools that can help researchers separate environmental contributions to language learning from genetic influences. Such insights could have important clinical applications.
To further that work, Michelson and Christy Hendrickson, PhD, associate professor of communication sciences and disorders, have submitted a grant proposal to support the next phase of research.
In addition to Michelson, Kasten and Tomblin, the research team included current and former UI researchers Dabney Hoffman, Savantha Thenuwara, Alison Momeni, Marlea O’Brien, Jeffrey C. Murray and Tanner Coomer (now with Recurson Pharmaceuticals). Taylor R. of the Center for Genomic Research at Massachusetts General Hospital. Thomas and Jin-Young Koh of the University of Maryland also contributed to the study.
The research was supported in part by the National Institute on Deafness and Other Communication Disorders and the National Institute of General Medical Sciences, both part of the National Institutes of Health, as well as the Roy J. It was funded by a grant from the Carver Charitable Trust.