A 1.8-million-year-old fossil may belong to the oldest right-handed human

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As any lefty knows well, our world is largely built for righties. Basic items from scissors and knives to cameras and computer mice are all designed to suit the roughly nine in 10 people who are right-handed.

New evidence suggests this lopsided split may date back more than a millennia, according to an international team of anthropologists.

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The largest intact Basulosaurus isis whale fossil, which is on display at the Wati El Hitan Fossils and Climate Change Museum, on the opening day, in the Fayoum oasis, Egypt, Thursday, Jan. 14, 2016. Egypt has cut the ribbon on the Middle Eastâs first fossil museum housing the world's largest intact skeleton of a "walking whale" in an attempt to attract much-needed tourists driven off by recent militant attacks. (AP Photo/Thomas Hartwell)
Fossilized whale bones are on display outside the Wati El Hitan Fossils and Climate Change Museum, a UNESCO natural World Heritage site, on the opening day, in the Fayoum oasis, Egypt, Thursday, Jan. 14, 2016. Egypt has cut the ribbon on the Middle Eastâs first fossil museum housing the world's largest intact skeleton of a "walking whale" in an attempt to attract much-needed tourists driven off by recent militant attacks.(AP Photo/Thomas Hartwell)
Fossilized whale bones are on display outside the Wati El Hitan Fossils and Climate Change Museum, a UNESCO natural World Heritage site, on the opening day, in the Fayoum oasis, Egypt, Thursday, Jan. 14, 2016. Egypt has cut the ribbon on the Middle Eastâs first fossil museum housing the world's largest intact skeleton of a "walking whale" in an attempt to attract much-needed tourists driven off by recent militant attacks.(AP Photo/Thomas Hartwell)
Guards stand outside the Wati El Hitan Fossils and Climate Change Museum, a UNESCO natural World Heritage site, on the opening day, in the oasis of Fayoum, Egypt, Thursday, Jan. 14, 2016. Egypt has cut the ribbon on the Middle Eastâs first fossil museum housing the world's largest intact skeleton of a "walking whale" in an attempt to attract much-needed tourists driven off by recent militant attacks. (AP Photo/Thomas Hartwell)
The largest intact Basulosaurus isis whale fossil, which is on display at the Wati El Hitan Fossils and Climate Change Museum, on the opening day, in the Fayoum oasis, Egypt, Thursday, Jan. 14, 2016. Egypt has cut the ribbon on the Middle Eastâs first fossil museum housing the world's largest intact skeleton of a "walking whale" in an attempt to attract much-needed tourists driven off by recent militant attacks.(AP Photo/Thomas Hartwell)
A visitor views the largest intact Basulosaurus isis whale fossil, which is on display at the Wati El Hitan Fossils and Climate Change Museum, on the opening day, in the Fayoum oasis, Egypt, Thursday, Jan. 14, 2016. Egypt has cut the ribbon on the Middle Eastâs first fossil museum housing the world's largest intact skeleton of a "walking whale" in an attempt to attract much-needed tourists driven off by recent militant attacks.(AP Photo/Thomas Hartwell)
Fossilized whale bones are on display outside the Wati El Hitan Fossils and Climate Change Museum, a UNESCO natural World Heritage site, on the opening day, in the Fayoum oasis, Egypt, Thursday, Jan. 14, 2016. Egypt has cut the ribbon on the Middle Eastâs first fossil museum housing the world's largest intact skeleton of a "walking whale" in an attempt to attract much-needed tourists driven off by recent militant attacks.(AP Photo/Thomas Hartwell)
Workers prepare the red carpet for VIP guests outside the Wati El Hitan Fossils and Climate Change Museum, a UNESCO natural World Heritage site, on the opening day, in the Fayoum oasis, Egypt, Thursday, Jan. 14, 2016. Egypt has cut the ribbon on the Middle Eastâs first fossil museum housing the world's largest intact skeleton of a "walking whale" in an attempt to attract much-needed tourists driven off by recent militant attacks.(AP Photo/Thomas Hartwell)
Egyptian Army vehicles stand outside the Wati El Hitan Fossils and Climate Change Museum, a UNESCO natural World Heritage site, on the opening day, in the Fayoum oasis, Egypt, Thursday, Jan. 14, 2016. Egypt has cut the ribbon on the Middle Eastâs first fossil museum housing the world's largest intact skeleton of a "walking whale" in an attempt to attract much-needed tourists driven off by recent militant attacks.(AP Photo/Thomas Hartwell)
A picture taken on January 14, 2015 shows a marine organism at the Wadi el-Haitan Fossil and Climate Change Museum in Fayoum, 60 km south of the Egyptian capital Cairo. / AFP / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
A picture taken on January 14, 2015 shows a marine organism at the Wadi el-Haitan Fossil and Climate Change Museum in Fayoum, 60 km south of the Egyptian capital Cairo. / AFP / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
A picture taken on January 14, 2015 shows a marine organism at the Wadi el-Haitan Fossil and Climate Change Museum in Fayoum, 60 km south of the Egyptian capital Cairo. / AFP / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
A picture taken on January 14, 2015 shows a whale's skeleton at the Wadi el-Haitan Fossil and Climate Change Museum in Fayoum, 60 km south of the Egyptian capital Cairo. / AFP / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
A picture taken on January 14, 2015 shows a marine organism at the Wadi el-Haitan Fossil and Climate Change Museum in Fayoum, 60 km south of the Egyptian capital Cairo. / AFP / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
A picture taken on January 14, 2015 shows a Basilosaurus whale skeleton at the Wadi el-Haitan Fossil and Climate Change Museum in Fayoum, 60 km south of the Egyptian capital Cairo. / AFP / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
A picture taken on January 14, 2015 shows a whale skeleton at the Wadi el-Haitan Fossil and Climate Change Museum in Fayoum, 60 km south of the Egyptian capital Cairo. / AFP / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
A picture taken on January 14, 2015 shows a whale skeleton at the Wadi el-Haitan Fossil and Climate Change Museum in Fayoum, 60 km south of the Egyptian capital Cairo. / AFP / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
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Researchers said a 1.8-million-year-old fossilized jaw bears the scratches of a person who was right-handed. This finding could help scientists better understand how the human brain developed and when we first developed language.

More from Mashable: Lucy, our early human ancestor, may have died after falling from a tree

The Homo habilis fossil is more than four times older than what scientists previously believed was the oldest fossil evidence of our right-handed tendencies, according to the study published Oct. 20 in the Journal of Human Evolution.

Three perspectives of the 1.8-million-year-old fossil.

The fossil discovery "may tell us something about when language first appeared," said David Frayer, the study's lead author and a professor of biological anthropology at the University of Kansas in Lawrence.

"Language, handedness, brain laterality — the difference in function between the left and right side of the brain — are all interrelated," Frayer told Mashable.

The study carries a big caveat.

Frayer and his colleagues were only able to study one Homo habilis fossil. If other scientists find evidence of a left-handed human ancestor from the same period, it would undermine this study's conclusions about when humans developed a common dominant hand.

"This specimen is only one, but we're hoping that people will find more, or look at more specimens," Frayer said.

Right v. Left

The prevalence of righties is a defining characteristic of our species.

Researchers estimate that about 90 percent of modern humans are right-handed. Neanderthals and pre-Neanderthals likely had a similar ratio of righties to lefties, according to fossil evidence dating back 430,000 years.

Left-handedness is less rare among U.S. presidents, it turns out. President Barack Obama followed seven 20th-century left-handed presidents, including Bill Clinton, George H.W. Bush and Ronald Reagan.

Apes, by contrast, are closer to a 50-50 split when it comes to right- and left-handedness.

The new study supports earlier evidence that Homo habilis were closer to modern humans than apes and that they had brain lateralization, meaning their right and left halves of the brain specialized in different functions.

In humans, the left half of the brain controls the right side of the body. The left side also plays a primary role in speech production and language comprehension. That is partly why scientists believe that our right-handedness is associated with our brain functions and language capacity.

"Neanderthals at least probably had language," Frayer said. He added that the Homo habilis fossil"is just the beginning to look for that kind of evidence in the earliest Homo [habilis]."

Scratched teeth

The 1.8-million-year-old upper jaw fossil was discovered in present-day Tanzania. Frayer and his colleagues determined the bone belonged to a righty by studying the scratch marks across six front teeth.

Because the scratches appeared only on the front of the teeth — not the backs or sides — the anthropologists surmised the early human nicked his or her teeth during a pre-historic feast.

Frayer described an individual clenching a strip of tough meat between her teeth. Her left hand pulled the other end tight, while her right hand used a sharp stone tool to scrape off easier-to-chew chunks. When her right hand slipped, the tool would have scraped her teeth, leaving diagonal grooves.

A) A right-hander pulls with the left and cuts with the right. B)  Dense concentrations of striations show that the tooth surface was repeatedly modified by a stone tool.

The anthropologists tallied 559 total marks on the six front teeth. About 47 percent of the scratches were slanted in the direction of a right-handed cut. About 11 percent of the scratches slanted the opposite direction, reflecting a left-handed cutting motion. The remaining scratches were horizontal or vertical.

"These teeth were used as platforms to process materials, and so there were lots of different scratches," Frayer said.

But the right-handed scratches were disproportionately high and statistically significant, leading the researchers to conclude that the jaw's owner was most likely right-handed.

It's possible that Frayer and his colleagues have misinterpreted these scratches.

Bernard Wood, a paleoanthropologist at George Washington University who was not part of the study, told the Christian Science Monitorthat Frayer and his colleagues might be jumping to conclusions.

"My concern is that they really don't spend enough time on other explanations for these phenomena, the presence of these scratches and their directionality," Wood said.

"It's a really interesting observation that only time will tell whether that observation has been over-interpreted."

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