A tiny portion of the human genome may have had a surprisingly large impact on our ability to develop language. New research suggests these genetic sequences were already present before modern humans and Neanderthals split from a common ancestor.
Published in Science Advances, the study comes from researchers at University of Iowa Health Care, who examined how specific genetic regulatory regions influence language ability. Their work combines modern genetic analysis with data collected from hundreds of students more than three decades ago.
Language is one of the traits most often associated with being human. Scientists have long tried to understand where this ability comes from and how it evolved. Rather than focusing on language itself, the new study looks at the genetic mechanisms that may have helped build the brain structures needed to support it.
Tiny Genetic Regions With A Major Effect
The researchers focused on Human Ancestor Quickly Evolved Regions, or HAQERs. These are not genes but regulatory sections of DNA that help control how genes are switched on and off.
According to Jacob Michaelson, a professor of psychiatry and neuroscience at the University of Iowa, HAQERs make up less than a tenth of a percent of the human genome. Yet the study found that they have around 200 times more impact on language ability than any other genomic region.
“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.
The team compares these regions to volume controls that regulate genetic activity. In that analogy, the well-known FOXP2 gene acts as one of the mechanisms adjusting those controls.
A Project Decades In The Making
The research has its roots in a study launched in the 1990s by Bruce Tomblin, now professor emeritus in the University of Iowa Department of Communication Sciences and Disorders.
At the time, Tomblin evaluated the language abilities of 350 students in Iowa and collected saliva samples for future research. The DNA remained stored until genetic sequencing technology became advanced enough to analyze it in detail.
As explained by the researchers, those samples eventually allowed Michaelson‘s team to investigate how differences in DNA relate to differences in language ability.
To explore when these genetic influences first appeared, the scientists developed a tool called an evolutionary-stratified polygenic score (ES-PGS). This approach enabled them to sort genetic effects according to their place in evolutionary history and trace them across roughly 65 million years.
“Hardware” May Be Older Than Thought
One of the study’s most notable findings is that these language-related regulatory regions were already present before the evolutionary split between modern humans and Neanderthals. These genetic signatures linked to HAQERs may even have been slightly stronger in Neanderthals than they are in people today.
“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 stated. “We can say humans at least had the ‘hardware’ for language earlier than what we previously thought.”
The researchers also looked at why these genetic regions appear to have remained stable over time. Their explanation involves a process known as balancing selection. The study noted that HAQERs contribute to fetal brain development and are linked to larger brain and skull size. At the same time, larger infant head size could make childbirth more difficult, creating limits on how far this pathway could evolve.
