Why did Neanderthals have such humongous right arms? (+video)
An analysis of Neanderthal bones indicates that they had disproportionately huge biceps and triceps on their right arms, and that spear thrusting does not seem to fully account for their lopsided muscles.
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In comparison, scraping tasks led to much higher muscle activity on the right side than on the left, suggesting they may explain the details often seen in Neanderthal skeletons.Skip to next paragraph
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"While hunting was important to Neanderthals, our research suggests that much of their time was spent performing other tasks, such as preparing the skins of large animals," Shaw said.
Animal skins would have been needed for clothes and shelters to stay warm in the cold climates Neanderthals often lived in. Scrapers are also among the most commonly found Neanderthal artifacts, which they used to scrape unwanted tissue off animal skins.
"If we are right, it changes our picture of the daily activities of Neanderthals," Shaw said. "This is a lot more mundane than hunting big game all the time, but it shows forethought to prepare skins for use throughout the year."
Modern humans lived at the same time and places as Neanderthals, but did not show the same dramatic lopsidedness, Shaw said. This suggests that modern humans may have scraped in a different way from their Neanderthal contemporaries — modern humans possessed more complex sets of tools, and so perhaps needed to scrape less intensely than Neanderthals did to prepare animal skins for effective use, Shaw conjectured.
The researchers do note that if Neanderthals were predominantly left-handed, that could also explain their results. However, they said that 90 percent of all modern humans are right-handed, a trend that might stretch back at least 10,000 years, and perhaps as far back as 500,000 or even 2 million years, and the same may have also held true for our closest known extinct relatives. "It's just very unlikely," Shaw said.
One might also ask if Neanderthal arms resulted from constant spear-throwing. However, the shape of the right Neanderthal humerus is generally rectangular, while modern humans that throw constantly have more rounded humerus bones, Shaw said.
Future research can look at skeletal remains of past groups of modern humans known to have worked on animal hides to see if they had similar features to Neanderthals. The scientists detailed their findings online today (July 18) in the journal PLoS ONE.
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