Eastern grey kangaroo manipulating food with one forelimb. Photo by Andrey Giljov/National Geographic Society
What do Barack Obama, David Bowie and the red kangaroo have in common? They’re all lefties. According to a new study from researchers at Saint Petersburg State University in Russia, two-legged marsupials not only exhibit handedness, but the overwhelming majority are left-handed.
Scientists once thought that handedness was unique to humans. But a new paper shows that handedness extends beyond our species. “All bipedal species have much greater strength of handedness,” said zoologist and study co-author Yegor Malashichev said.
The report found that similar to primates, if a marsupial walks upright, then it likely has a preference for one hand. Red kangaroos, the marsupial heavyweights that bounce about on two feet, were nearly 40 percent more likely to use their left hand than ambidextrous sugar gliders, whose acrobatic tendencies require four limbs to get around.
While close to 90 percent of humans are right-hand dominant, red kangaroos, red-necked wallabies, eastern grey kangaroos and brush-tailed bettongs display a strong left-handed dominance. This report by Malashichev and his colleagues, published today in the journal, Current Biology, theorizes that the preference for right vs left is due to anatomical differences in the brains of humans and marsupials.
In humans, handedness is lateralized, meaning that for most human ‘righties,’ the left side of the brain controls the right hand — and vice versa for lefties. The right hand is then able to coordinate with the left hand thanks to the corpus callosum, a broad band of nerve cables that connect the left and right brain hemispheres. Marsupials don’t have a corpus callosum, so their brain hemispheres must be communicating in a different way, but the researchers don’t know how yet.
Malashichev points out that a few diseases are associated with left handedness, including schizophrenia. Understanding how the marsupial brain is wired may provide insight into these disorders, he said.
So when you’re celebrating the lefties you love on August 15th, International Left-Hander’s Day, don’t forget about the kangaroos.
Eastern grey kangaroo (Macropus giganteus) are bipedal — walk on two legs instead of four — and are primarily left-handed, according to a June 18 study in Current Biology that was supported by the National Geographic Society Committee for Research and Exploration.
Goodfellow’s tree-kangaroos (Dendrolagus goodfellowi) walk on all fours and are thus ambidextrous, according to a June 18 study in Current Biology that was supported by the National Geographic Society Committee for Research and Exploration.
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