Modern day kangaroos can use all fours or hop. But their ancestors who roamed Australia about 100,000 years ago were walk upright on two legs, just like humans. Scientists reached this conclusion after analyzing bones of the extinct kangaroos. Called Sthenurine, the giant rabbit-faced creatures weighted about 550 pounds, almost three times the weight of the modern ones. They lived in the Pleistocene era, and disappeared around 30,000 years ago.
Sthenurine was incapable of moving on all fours
Scientists found that the ancient kangaroos had spines and hind limbs that were different from their modern counterparts. Christine Janis of Brown University said it was unlikely that a 550-pound animal would be able to hop. Fossils provide great clues that the extinct animals were doing something different from the living forms. Findings of the study appeared in the journal PLOS ONE.
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Today’s red and gray kangaroos move about on all fours for slow speed and hop at fast speeds. That requires a sturdy tail, flexible backbone and hands capable of supporting their body weight. But the Sthenurines lacked all of those attributes, making them ill-suited for bouncing but well-suited for walking.
Ancient kangaroos were an easy target for hunters
In the big-boned roos, the tibia had a flap of bone that provided extra flexibility. Moreover, they had relatively larger knee and hip joints. Their broad, flared pelvis would allow for more gluteal muscles, which would help them balance their body weight on one leg at a time. Past studies have shown that the Sthenurines’ hands were not not suitable to support the all-fours. Instead, their hands were specialized for foraging.
In terms of biomechanics, it’s impossible to hop at slow speeds, especially when the animal weighs as much as 550 pounds. But it had to move somehow. Scientists believe their slow locomotion might have made them a favorite target for human hunters, which explains their extinction about 30,000 years ago. Early humans reached Australia more than 50,000 years ago.