It isn't just recently that humans have hunted animals to extinction. It appears that 100,000 years ago a giant kangaroo lived in the Australian Outback, where it walked instead of hopped. But perhaps due to its slowness, the creature was an easy target for hunters who arrived somewhere between 40,000 and 60,000 years ago. By 30,000 years ago, the lumbering family of kangaroos was extinct. Called "sthenurines," the kangaroos were up to three times the size of modern ones; sported larger bones and larger hip and knee joints; and had a larger pelvis to help balance while shifting between feet, reports the Telegraph. What they didn't have: the flexible backbone and hefty tail that today's kangaroos do.
"We've known for a while that sthenurines were different in their dietary behavior," the lead author of the paper, published in PLoS One, tells the BBC. What they're finding now is that the extinct kangaroo was stocky at up to 550 pounds (the BBC points out that's bigger than a male lion), stood nearly 7 feet tall, and had only one toe on each hind foot, compared to the modern version's four. "The biggest ones got to a size that does strain the credulity of hopping," says Christine Janis. "Obviously you're going out on a limb when you're proposing something about an extinct animal. But all the data fit." The concept of walking instead of hopping is bizarre but not unprecedented: Some tree kangaroos in Papua New Guinea are reportedly bipedal. (Meanwhile, scientists think of the large tail of today's kangaroos as a fifth leg.)