Most people today are right-handed—in fact, about 90% of the human population favors their right hand over their left.
But when did this preference begin? Was it always part of human evolution, or did it emerge more recently?
A newly analyzed 1.8-million-year-old fossil may provide the earliest evidence of right-handedness in our evolutionary history.
The fossil, known as OH–65, belonged to a member of the species Homo habilis—one of our earliest known ancestors.
But how can scientists determine handedness from a fossil?
It all comes down to tiny scratches on the teeth.
These scratches, called labial striations, run from left to right across the front teeth, suggesting that this early human ancestor used a stone tool in their right hand while stabilizing food with their left.
If confirmed, this discovery would push back the earliest evidence of right-handedness by more than 1.3 million years.
But what does this mean for human evolution?
And could it be linked to something even bigger—the development of language?
The 1.8-Million-Year-Old Clue Hidden in a Jawbone
The fossil in question—OH–65—was discovered in 1995 in a stream channel at Olduvai Gorge, Tanzania, a site famous for its rich collection of hominin fossils.
At first glance, it looked like just another jawbone. But upon closer inspection, researchers noticed something unusual:
- The fossil consists of an intact upper jaw with all of its teeth, along with part of the lower face.
- A closer analysis revealed numerous tiny scratches on the lip-facing side of the front teeth.
- These scratches were not random—they almost all angled from left to right.
How Do These Scratches Reveal Handedness?
According to David Frayer, an anthropologist from the University of Kansas:
“Experimental work has shown these scratches were most likely produced when a stone tool was used to process material gripped between the anterior teeth and the tool occasionally struck the labial face, leaving a permanent mark on the tooth’s surface.”
In other words, the individual likely:
- Held a piece of food in their teeth.
- Pulled it taut with their left hand.
- Used a stone tool in their right hand to cut it.
And every so often, that tool accidentally scraped the teeth—leaving behind these tiny marks that survived for nearly 2 million years.
This makes OH–65 the earliest known potential right-hander in the fossil record.
Was Right-Handedness Always This Common?
Most people today are right-handed, but why?
Many scientists assumed right-handed dominance appeared much later in human evolution—perhaps around 500,000 years ago, when Neanderthals left behind evidence of handedness in their fossils.
But if Homo habilis was already showing a preference for the right hand 1.8 million years ago, then this trait could be much older than we ever thought.
This challenges the common belief that right-handedness emerged relatively recently.
Instead, it may have been a defining trait of early hominins—one that set the stage for important evolutionary changes.
So, what makes handedness so significant? It may hold the key to something even more profound:
The origins of human language.
Could Handedness Be Linked to Language?
Handedness isn’t just about which hand you use—it’s deeply connected to brain structure.
In modern humans, the left hemisphere of the brain is responsible for both hand control and language processing.
Studies show that:
- The vast majority of right-handed people process language on the left side of the brain.
- Even many left-handed people still have left-hemisphere dominance for language.
This suggests that right-handedness and language may have evolved together, shaped by the same neural developments.
Frayer explains:
“Handedness and language are controlled by different genetic systems, but there is a weak relationship between the two because both functions originate on the left side of the brain.”
If Homo habilis was already displaying right-handedness, it suggests their brains were already undergoing reorganization—perhaps laying the foundation for complex communication and, eventually, language.
Of course, one fossil alone isn’t enough to prove this theory.
But if scientists find more early hominin fossils with similar right-handed indicators, it could change how we understand the evolution of both handedness and speech.
Why Are Most People Right-Handed? The Mystery Remains
Even with this new evidence, scientists still don’t fully understand why right-handedness became dominant.
Some possible explanations include:
1. A Survival Advantage
- Right-handedness may have given early humans an advantage in tool-making and hunting.
- Coordination and skill with one dominant hand might have improved efficiency.
2. Social and Cultural Influence
- In many ancient societies, the right hand was associated with purity, strength, and skill, while the left was sometimes stigmatized.
- This cultural reinforcement may have played a role in cementing right-hand dominance over time.
3. Brain Asymmetry and Genetics
- The left hemisphere controls the right side of the body and is also the language center.
- Some researchers believe genetic factors may have favored right-hand dominance because it was linked to brain efficiency.
However, despite centuries of research, the true cause of handedness remains a mystery.
What’s Next? The Future of Handedness Research
The discovery of OH–65 provides an exciting new clue in the mystery of handedness. But to confirm that right-handedness was common in Homo habilis, researchers will need:
- More fossils from the same time period.
- More detailed studies of tooth scratches, bone structures, and tool-use patterns.
- A better understanding of how handedness connects to brain evolution.
If right-handedness truly emerged 1.8 million years ago, it means that our ancestors were already developing specialized brain functions long before modern humans appeared.
And if those same brain changes were linked to language development, this discovery could help unlock one of the greatest mysteries of human evolution:
When—and how—did we first begin to communicate?
A Tiny Jawbone, A Big Discovery
A few small scratches on a 1.8-million-year-old tooth may not seem like much.
But those tiny marks could reveal something profound:
- Right-handedness may have existed far earlier than we thought.
- It could be linked to the development of the modern human brain.
- It may even hold clues about the origins of language.
And the best part? This is just the beginning.
As more fossils are uncovered, scientists may finally be able to answer:
Did Homo habilis think and communicate in ways more similar to us than we ever imagined?
Let’s hear your thoughts. Could this fossil rewrite our understanding of handedness and brain evolution?
