Giants once ruled the planet, and it was more recent than you think. After the dinosaurs departed the Earth 65 million years ago, they left a void, and mammals stepped in to take their place. During the Pleistocene (2 million to 11,700 years ago), giant mammals, called megafauna, roamed nearly every continent on the planet. Mastodons, giant deer, and even giant beavers roamed North America, while the giant sloth, armadillo, hippo inhabited South America. The cave bear, wooly rhinoceros, and giant polar bears roamed Europe and Asia. Australia also had mammals in the game, like the giant kangaroo.
Take a moment and imagine Australia. Chances are you envision kangaroos hopping across the outback. Or dingos. The largest variety of kangaroo today — the red kangaroo — weighs almost 200 pounds and stands over 5 feet in height. However, kangaroo fossils from the Pleistocene, dated at 30,000 years ago, indicate that these animals weighed more than 500 pounds. Now imagine these massive roos hopping across the idyllic red rocks of the outback. It takes on a slightly more, er, menacing flavor.
Hopping is the quintessential kangaroo gait and a very efficient form of locomotion. However, just because kangaroos hop today does not mean it was common in extinct species. Besides a massive body structure, the ancient giant kangaroo was distinguished by its short face, specialized arms and hands, and robust limb bones. After considering the massive size and structure of the giant kangaroos, scientists propose that each limb had the ability to bear the full weight of the animal. As such, the giant kangaroo had the ability to walk with a bipedal motion, similar to humans. Hopping was probably out of the question.
So what happened to the giant kangaroo and all of the other megafauna? Scientists have several ideas to explain their disappearance from the planet. About 20,000 years ago, the most recent glacial episode reached its height. At that time, food supplies were limited, possibly providing the death blow to these giant creatures. Other scientists have suggested a more cataclysmic departure a la a comet, similar to what probably killed off the dinosaurs. Other scientists suggest that the rise of humans resulted in overhunting and the inevitable extinction of these massive creatures. Finally, disease is always a possibility for an extinction event. Although the cause for the extinction of megafauna more than 10,000 years ago remains to be seen, it seems clear that giant kangaroos weren’t hopping to their destruction.