Here’s an interesting bit of information for your next trivia night: by and large, kangaroos are left-handed. This might seem like really weird news, but the study that backs this up may help scientists get a better handle on the evolution of mammals — in addition to dispelling the notion that true “handedness,” the tendency to favor one limb over another, is uniquely human trait.
“We found a pronounced degree of handedness in an animal group only distantly related to humans,” says Yegor Malashichev, a zoologist at Saint Petersburg State University and a co-author of the study published in Current Biology today. And the degree of handedness was “comparable to that in our species.”
No too long ago, researchers thought of handedness as a trait only humans possessed. That notion has changed somewhat over the last few decades, as scientists demonstrated that hand preferences and other behavioral lateralization relating to brain asymmetry are “much more widespread spread in the animal kingdom than previously thought,” Malashichev says. These preferences have even been found in bees, worms, and frogs that walk instead of jump. But, for the most part, the degree of handedness that we’ve seen in non-primates hasn’t been as strong as what we see in humans, and it tends to be related to specific behaviors and tasks, instead of a general way of approaching the world, as is the case with humans.
Now, “this last bastion has fallen,” Malashichev says. Researchers have found a group with the same pattern of handedness as the one seen in humans. “So, we can say that kangaroos possess not just some population level preferences in certain actions, but possess real true handedness, like humans have,” he says. “In this respect, they appear to be more lateralized, or handed, than many of primates and even Great Apes.”
As you might have guess, Malashichev and his colleagues spent a lot of time observing kangaroos before they reached this conclusion. They observed seven species of marsupials living in the wild. Those species included red-necked wallabies, Goodfellow’s tree kangaroo, the eastern grey kangaroo, and the red kangaroo. The scientists watched them as they groomed themselves, grabbed food with their paws, and leaned on their forearms while feeding on grass. And throughout this period, they collected data relating to hand preference for a set of tasks.