A magazine for friends of the Warren Alpert Medical School of Brown University.

Hop-less Wanderers


These roos were made for walking. 

Long before humans set foot o n Australia, another bipedal mammal may have been ambling around the outback. According to a study of 100,000-yearold bones, a now-extinct family of kangaroos likely walked on two feet.

The sthenurine roos didn’t look a whole lot like the marsupials we know today. They had round, rabbit-like faces, and they were huge—up to 550 pounds; the modern red kangaroo tops out at 200 pounds. But it’s their skeletal structure that really set the ancient animals apart.

Using measurements of thousands of bones from dozens of kangaroo and wallaby species, Christine Janis, PhD, professor of ecology and evolutionary biology, and her research team hypothesize in a paper in the journal PLOS ONE that
the anatomy of the Pleistocene-era sthenurines was better suited to walking, with an ankle structure that favored putting down one foot at a time, a relatively inflexible spine, and bigger hip and knee joints.

Their large size and big bones, furthermore, would have hindered hopping. “I don’t think they could have gotten that large unless they were walking,” Janis says.

For reasons yet unknown—perhaps because they were too slow to elude human hunters when they arrived on the scene, or unable to migrate long distances in search of resources as Australia’s climate became more arid—the lumbering sthenurines died out around 30,000 years ago. Until scientists find more evidence, such as a preserved set of tracks, they won’t know for certain whether sthenurines walked or hopped into the evolutionary sunset.



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