AILSA CHANG, HOST:
Hopping has evolved multiple times in the animal kingdom. Think grasshoppers, frogs, rabbits. But maybe the bounciest of the group would be kangaroos, which can hop and hop and hop with amazing efficiency, right?
PETER BISHOP: As they go faster, they don't actually use any extra energy. They essentially use the same amount of energy regardless of how fast they are hopping.
JUANA SUMMERS, HOST:
Peter Bishop of Harvard's Museum of Comparative Zoology says scientists know a bit about how that works.
BISHOP: Kangaroos have very long hind limbs, very long legs, and they have very, very long tendons. And so they're essentially bouncing along on a set of, like, rubber bands, almost - very elastic. So they can bounce and recoil and recover a lot of their energy from step to step.
SUMMERS: But a bigger question is how kangaroos' superpower came to be. To investigate, Bishop and his colleagues turned to a sort of evolutionary second cousin of the kangaroo, a rat-looking creature called the musky rat-kangaroo.
BISHOP: It's kind of stocky, small, forages about in the tropical rainforests, doesn't look a thing like what you would typically associate with a kangaroo. It's not large, lanky, bouncing about on these two very long hind legs.
CHANG: No. In fact, it is not known to hop on its hind legs at all, which is why they wanted to study it - to see if this pudgy, brown critter might hold clues about how protokangaroos moved.
SUMMERS: So to study the tiny 'roo, the researchers set up cameras in the rainforests of northern Australia and filmed the animals kind of scurrying around. Then they used software to analyze the videos, deconstructing the musky rat-kangaroos' gait frame by frame, and they found...
BISHOP: Even at their fastest speed, they always stayed on four legs. They bounded along.
CHANG: And the way they bounded along was revealing.
BISHOP: As they move, their hind limbs always move together as a pair. And that is telling us that that could be a precursor to the bipedal kangaroos because they also move their hind limbs in pairs.
CHANG: The findings appear in the journal Australian Mammalogy. Bishop says the work gives scientists insights into how kangaroo hopping might have evolved and perhaps new ideas as well for robots or prosthetic devices based on jumpers like the kangaroo.
BISHOP: They've been figuring out essentially the same kinds of problems that engineers and roboticists are trying to work out.
SUMMERS: But the animals have already got a huge jump - get it? - on human technologists by tens of millions of years.
(SOUNDBITE OF NATHANIEL DREW X TOM FOX'S "MEU JEITO") Transcript provided by NPR, Copyright NPR.
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