How did humans start talking? Scientists may have found the answer

A newly identified version of a gene in the human genome appears to have influenced our capacity for complex speech, distinguishing our species from close relatives like Neanderthals and Denisovans. 

This finding could help explain why Homo sapiens alone developed sophisticated language, an ability that underpins much of our culture and technology.

A team of researchers led by Rockefeller University has pinpointed a particular protein variant – found only in modern humans – that alters vocalization. 

When introduced into mice, this version of a gene called NOVA1 changed the ultrasonic calls the animals produce, hinting at its potential role in the evolutionary roots of human speech.

Genetics behind complex speech

Modern humans have long been known to possess numerous adaptations in their anatomy and nervous system that enable speech, including specialized vocal tracts and brain regions devoted to language processing. Yet the genetics behind this capacity remains poorly understood. 

One candidate gene, FOXP2, has been linked to speech and language disorders in people, but evidence suggests Neanderthals also possessed the same FOXP2 variant – leaving open questions about what truly sets humans apart.

The team behind the current study focused on NOVA1, first identified in the early 1990s for its essential contribution to brain function. 

“Such changes may have played important roles in the acquisition of characteristics that have contributed to the emergence, expansion, and survival of Homo sapiens,” said first author Yoko Tajima, a postdoctoral associate at Rockefeller University. 

Researchers have found that variants of NOVA1 are associated with language and motor difficulties, underlining the gene’s profound influence on neural development.

Unlike the versions of NOVA1 that appear in other mammals, birds, and even archaic humans, the form carried by modern humans contains a single amino acid substitution referred to as I197V. This difference, though seemingly small, may have had outsized consequences.

A surprising twist 

To explore the functional impact of I197V, scientists used CRISPR editing to replace the standard NOVA1 gene in mice with the human-specific variant. They then examined how this change altered the animals’ brain activity. 

Initially, there was no detectable shift in the genes responsible for motor control or overall neural development – implying the mice developed normally in most respects.

Soon, however, a critical clue emerged: many of the transcripts affected by the human NOVA1 variant were tied to vocalization. 

Study leader Robert B. Darnell is head of the Laboratory of Molecular Neuro-Oncology at Rockefeller. 

“We found that when we ‘transliterated’ the squeaks made by mice with the human-specific I197V variant, they were different from those of the wild-type mice. Some of the ‘letters’ had changed,” said Darnell. “It was one of those really surprising moments in science.”

When the team tested how adult male mice “spoke” to female mice during mating attempts, they discovered that the engineered mice produced distinct vocal patterns. 

“They ‘talked’ differently to the female mice,” Darnell noted. “One can imagine how such changes in vocalization could have a profound impact on evolution.”

Archaic humans and complex speech

To determine whether this genetic alteration was unique to Homo sapiens, the researchers compared modern human NOVA1 to the genomes of Neanderthals and Denisovans, human relatives who lived tens of thousands of years ago. 

Both archaic lineages possessed the older NOVA1 form seen in other species – lacking the I197V substitution. A further check of over 650,000 modern human genomes revealed that nearly everyone carries the I197V version of NOVA1, solidifying its status as a widespread and defining feature of our species.

“This gene is part of a sweeping evolutionary change in early modern humans and hints at potential ancient origins of spoken language,” Darnell said. “NOVA1 may be a bona fide human ‘language gene,’ though certainly it’s only one of many human-specific genetic changes.”

Future research directions

While NOVA1’s impact on speech is not yet fully understood, these findings open important research paths. Future work could examine how this human-specific variant contributes to developmental disorders, including those affecting language. 

“Our discovery could have clinical relevance in many ways, ranging from developmental disorders to neurodegenerative disease,” Darnell said.

NOVA1’s neural pathways might help explain why some conditions prevent speech or hamper vocal communication. 

The gene has been associated with autism spectrum disorder, and earlier studies from the same group reported a patient with mutations in NOVA1 who presented speech delays, among other neurological issues. Investigating how I197V influences brain circuitry could yield insights into such disorders.

Language and human uniqueness

The capacity for complex speech, coupled with advanced cognitive functions, has propelled humans to remarkable achievements – from passing down knowledge orally to building global civilizations. 

This study highlights that our linguistic edge may be rooted in subtle but pivotal genetic differences – differences that evolved after our lineage diverged from archaic humans.

Though the NOVA1 variant alone does not explain why humans can speak while other hominids could not, it highlights one of the many genetic innovations underlying our species’ linguistic abilities. 

With further work, scientists hope to piece together more of the molecular puzzle behind language, offering a glimpse into what truly made Homo sapiens the world’s great storytellers.

The study is published in the journal Nature Communications. 

Image Credit: Laboratory of Molecular Neuro-oncology at The Rockefeller University

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