Some giant extinct kangaroos were too heavy to jump—they had to walk like Godzilla
Fossils show giant kangaroos weighing up to 270 kilograms; skeletal evidence suggests they couldn't jump; Pleistocene footprints confirm at least one species walked on two feet.
The video won't play here. Listen to the audio instead:
The argument · tap a timestamp to hear it
Kangaroos are four Australian species, but the family Macropodidae contains 63
The four species Australians recognize as 'kangaroos'—red, eastern gray, western gray, and musky rat-kangaroo—are just the famous ones. The broader family Macropodidae contains 63 recognized species, including quokkas, tree-kangaroos, and brush-tailed bettongs. All share nearly identical body proportions, merely scaled to different sizes: the red kangaroo stands over two meters tall and weighs up to 90 kilograms (200 pounds), while some species are smaller than half a meter. Like how only a few cat species became household names, most kangaroo relatives never entered public awareness.
Kangaroos evolved to walk on the outer two toes, not the middle
The kangaroo foot is unique. The second and third toes are fused into a thin, single-looking bone; the first toe (big toe) disappeared entirely. The actual weight-bearing falls on the fourth and fifth toes—the outer edge of the foot. This is the opposite of horses, deer, and most mammals, which carry weight down the centerline. This outer-toe specialization is entirely unique to kangaroos and represents a separate evolutionary solution for high-speed bipedal hopping, which explains why their hind feet look so long and distinctive.
Kangaroo molars move forward as a conveyor belt system, not like humans
To combat silica and sand in grass, kangaroos didn't evolve high-crowned teeth that grow throughout life like horses do. Instead, they evolved "marching molars"—a conveyor-belt system where worn molars at the front fall out after being reduced to stumps, and new molars behind advance forward to replace them in sequence. It's a relay system entirely unlike human dentition. Today, only elephants, manatees, and kangaroos use this pattern. Once all the molars are used up, the animal starves—there are no replacements left.
Faster jumping costs kangaroos almost no extra energy—a speed-independent efficiency
Research shows that as kangaroos increase their hopping speed, the energy cost per unit distance barely increases. This is completely different from dogs, whose energy expenditure jumps sharply when moving from a trot to a sprint. The secret is the Achilles tendon. On landing, it stretches like a rubber band and stores energy; on takeoff, it releases that energy to the next hop. Large kangaroos recover roughly 50 percent of their energy this way. This efficiency advantage only appears in individuals heavier than about four kilograms; the larger the kangaroo, the more advantageous jumping becomes.
The narrative that kangaroos out-competed wombats may oversimplify the ecological story
The common story is that as climates dried and grasslands expanded, kangaroos adapted to open country and out-competed wombat relatives—including giant diprotodontids—for the herbivore crown. But researchers caution that this competitive-displacement narrative may oversimplify. It's equally plausible that environmental change punished wombats and rewarded kangaroos independently, with no direct battle for grassland happening at all. Humans instinctively frame evolution as clear victor-and-loser, but reality may be more ambiguous: two lineages responding separately to climate pressure rather than fighting over the same ecological niche.
Early kangaroos evolved such prominent fangs one species was named Fangaroo
Balbarids (Balbaridae) are among the most primitive known kangaroo relatives. One species had upper canines that curved and protruded—twice as long as its neighboring teeth—probably visible even with the mouth closed, much like musk-deer tusks. These likely served for intra-species display or combat rather than hunting. The teeth were so distinctive that researchers informally called it "Fangaroo," and that nickname was eventually adopted as its formal species name.
One extinct kangaroo evolved meat-cutting teeth, suggesting it hunted like a carnivore
The extinct genus Facowombia was a robust kangaroo, weighing 10–20 kilograms with a thick skull and powerful jaw muscles. It evolved carnassial teeth—the meat-cutting molars that dogs and cats use to slice flesh. Its tooth proportions closely match those of modern omnivorous canids like foxes. This animal almost certainly did not pursue prey at high-speed bipedal hops. Instead, it probably stalked on four legs, using its sturdy skull and blade-like lower incisors to subdue prey—a very different life from its grass-eating cousins.
Giant extinct kangaroos over 270 kilograms probably walked rather than jumped
The short-faced giant kangaroo stood close to three meters tall and weighed about 230 kilograms (500 pounds or more). An unnamed, later Pleistocene species may have weighed as much as 270 kilograms (600 pounds)—the heaviest kangaroo known. Calculations suggest a hopping weight limit of roughly 130–160 kilograms (300–350 pounds); these giants exceeded it. Their wider pelvises, knee joints, and increasingly upright posture all suggest bipedal walking rather than jumping. Tendon strength tests showed they could theoretically jump, but only within an extremely narrow window—about 9.4 kilometers per hour. Any faster and the tendons would snap; any slower and the metabolic cost would be prohibitive. The final evidence came from Pleistocene footprint trails: a series of alternating footprints that confirm at least one giant kangaroo species walked on two feet, step by step.
In their own words · checked verbatim
There are 63 recognized species in this family.
Their fourth toe is the big toe. It's the big main toe. It's the main weight bearing toe.
this feels like an evolutionary hack like a cheat it should not work as well as it does
And they also have the best-named kangaroo for one of the coolest reasons, Balbaru Fangaroo, the Fanged Kangaroo.
They evolved molars that are meant to slice meat.
That is the biggest size estimate of any macropod, any kangaroo we have ever found.
definitely can rule out swimming because you can't swim on land.
Figures
| Macropodidae species count | 63 recognized species | 53:03 |
| Red kangaroo standing height and weight | Over 2 meters tall; up to 90 kilograms (200 pounds) | 1:02:16 |
| Eastern gray kangaroo running speed | About 40 miles per hour (60 kilometers per hour) | 1:28:40 |
| Large kangaroo Achilles tendon energy recovery | Approximately 50 percent | 1:26:30 |
| Short-faced giant kangaroo weight estimate | About 230 kilograms (500 pounds or more) | 2:07:41 |
| Unnamed late-Pleistocene giant kangaroo weight estimate | About 270 kilograms (600 pounds) | 2:11:54 |
| Bipedal hopping weight limit estimate | Approximately 130 to 160 kilograms (300 to 350 pounds) | 2:16:01 |
| Giant kangaroo feasible jumping speed range | About 9.4 kilometers per hour | 2:20:13 |
Glossary
- Marching molars
- A conveyor-belt dental system where worn molars fall out and new ones advance forward to replace them in sequence, found only in elephants, manatees, and kangaroos.
- Pentapedal locomotion
- Movement using five limbs—in kangaroos, the tail acts as a fifth leg for balance and support during slow movement or rest.
- Carnassials
- Specialized meat-cutting molars evolved in carnivores like dogs and cats, adapted for slicing through flesh rather than grinding plant material.
- Macropod
- Literally 'big foot'; the formal name for the family Macropodidae, encompassing all kangaroos, wallabies, and related large-footed marsupials.
How to listen
Museum enthusiasts and biology students interested in mammalian biomechanics, Australian paleontology, or marsupial evolution.
The first ~50 minutes cover dinosaur body temperature, starfish ancestry, sauropods, and new cat species—unrelated to the kangaroo segment and skippable.