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Can Animals Be Right- or Left-Pawed?<br>Many creatures favor one side of the body over another, just as humans do. Scientists are interested in learning what makes animals right or left-pawed, so to speak, because it offer fascinating insights into evolution and brain development.<br>Written byJoshua Rapp LearnJoshua Rapp Learn

Joshua Rapp Learn is an award-winning D.C.-based science journalist who frequently writes for Discover Magazine, covering topics about archaeology, wildlife, paleontology, space and other topics.<br>View Full Profile.<br>Learn about our Editorial Policy.

2021-01-15T17:25:00 | 4 min read

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Humans live in a right-handed world. Estimates vary, but some 75 to 90 percent of us use our right hands as our “write hands.” If our species has dominant sides, it begs the question: How common is this trait across the animal kingdom? Are our near-cousins, like chimpanzees, right-handed or left-handed? And what about animals like whales that don’t even have hands? If an octopus had to high-five, which tentacle would it use?<br>div]:relative" data-ad-mapping="inline" data-ad-slot="Discover/inline-ad" id="div-inline-ad-playwire-inbody-shared">

For many years, scientists thought that handedness was unique to humans. But according to a growing body of research, many animals do have a preferred hand, limb, or even tentacle, and it likely starts in the brain.<br>“As soon as you have two sides of the brain, they start task-dividing,” says Ruth Byrne, a biologist who’s studied handedness in octopuses.<br>The $5 word that describes this phenomenon is biological chirality. Essentially, it describes a type of asymmetry that can be expressed either physically — say, one hand being a little bigger than the other — or a behavioral tendency to favor the use of one side over the other.<br>div]:relative" data-ad-mapping="inline" data-ad-slot="Discover/inline-ad" id="div-inline-ad-playwire-inbody-mobile-1">

This can be expressed on an individual and a population level. And researchers have found evidence of favoring one side over the other in a whole host of other life-forms. Most other primates tend to have a specific preference, and scientists even wrote an entire book on the handedness of plants that shows some plants have preferred directions of stem coiling or tendril reaching. Like the majority of humans, walruses often prefer their right flipper. Even slime molds — brainless, single-celled organisms — may turn right more often than left.<br>div]:relative" data-ad-mapping="inline" data-ad-slot="Discover/inline-ad" id="div-inline-ad-playwire-inbody-desktop-1">

Runs in the Family<br>The question of why humans are right-handed is still up for some debate, but some researchers believe we may have inherited our right-handed bias from our evolutionary ancestors. The left side of the human brain, commonly tasked with things like science, logic, language, controls the right side of our bodies, just as it does with our primate ancestors. Some researchers believe the development of the left side of the brain for speech and language might have also led to our right-handed bias among humans, though this isn’t completely understood.<br>Great apes, our closest primate relatives, are mostly right-handed, says William Hopkins, director and chairman of the Keeling Center for Comparative Medicine and Research at the University of Texas. When you measure behaviors like which hand they use to throw, chimpanzees and other great apes show a 65 to 70 percent bias for the right hand.<br>div]:relative" data-ad-mapping="inline" data-ad-slot="Discover/inline-ad" id="div-inline-ad-playwire-inbody-mobile-2">

“They do show what we would call a population-level bias, but there’s a couple of caveats to that,” Hopkins said.<br>Not all studies agree on the proportion of lefties or righties in a particular species. Part of the reason is researchers don’t always compare apples to apples. Humans might skew right-handed more often when it comes to writing, for example, but we often hold the paper with our left hand. If we were to climb a fruit tree, would we hold onto the trunk more often with our left or our right hand when reaching for fruit? Sometimes it’s hard to make direct comparisons between species that don’t necessarily spend the bulk of their time in the same types of activities.<br>div]:relative" data-ad-mapping="inline" data-ad-slot="Discover/inline-ad" id="div-inline-ad-playwire-inbody-desktop-2">

What Explains Southpaws?<br>Some researchers believe that deep in our evolutionary past, primates used to be mostly left-handed, but evolution or changes in behavior led to a switch over time. As a result, some of our more distant ancestors like lemurs tend to be also left-handed, says Stephanie Poindexter, a biological anthropologist at the State University of New York at Buffalo. But she...