Genetic "Volume Knobs" for Language Found in Ancient DNA Regions
Researchers at University of Iowa Health Care have identified specific genetic sequences that have a disproportionate impact on human language abilities. These sequences, called Human Ancestor Quickly Evolved Regions (HAQERs), represent less than 0.1% of the genome but, according to the researchers, drive approximately 200 times more impact on language ability than other genomic regions. The study was published on April 22 in Science Advances.
The Foundation of the Discovery
The research builds on foundational work from the 1990s by Bruce Tomblin, who studied language abilities in 350 Iowa students and preserved their DNA. Decades later, Jacob Michaelson's lab completed gene sequencing of that DNA with funding from the National Institutes of Health. The team then developed an innovative evolutionary-stratified polygenic score to examine 65 million years of evolutionary history.
What Are HAQERs?
HAQERs are not genes themselves, but regulatory regions that influence gene expression. Senior author Jacob Michaelson, PhD, described them as acting like "volume knobs" on genes.
The well-known FOXP2 gene, previously linked to language impairment, is described in this framework as "one of the hands that is turning these volume knobs." This clarifies its role, showing it works by regulating other genes through these HAQER sequences.
An Ancient Origin for Language Hardware
A key finding is that these genetic sequences evolved before humans and Neanderthals diverged and were present in Neanderthals, possibly even more prominently than in modern humans.
This suggests humans had the genetic "hardware" for language earlier than previously thought.
Why Did Evolution Pause Here?
The researchers propose that HAQERs remained relatively constant over deep time due to balancing selection—a form of natural selection that maintains genetic variation. They state that HAQERs promote fetal brain development and increase brain and skull size.
Before modern medicine, there was a physical limit to how large a baby's head could become before delivery became dangerous for both mother and child. This created an evolutionary ceiling.
"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," Michaelson said. "While other aspects of genetics that improve brain development for higher intelligence but don't directly affect fetal brain size, continued to evolve."
The Path Forward
The researchers plan to study the original cohort's families to separate direct genetic effects from environmental influences on language development. A major goal is to distinguish between the direct effect of a child's own genes and "genetic nurture," where parents' genetics influence the environment they create for their children.
Michaelson has submitted a grant with colleague Kristi Hendrickson to complete this next phase of the study.
Research Team & Funding
- Senior Author: Jacob Michaelson, PhD
- First Author: Lucas Casten, PhD
- The team included current and former University of Iowa researchers and collaborators from Massachusetts General Hospital and the University of Maryland.
- Funding was provided by the National Institute on Deafness and Other Communication Disorders, the National Institute of General Medical Sciences, and the Roy J. Carver Charitable Trust.