The unlikely journey of Australia's bipedal marsupials

Nature · Published 25 October 2026 Swipe more like this →

In short: Kangaroos are among the only animals on Earth to walk upright like humans or birds, yet their evolutionary path was anything but direct. From ancient forests to vast grasslands, these marsupials underwent a radical transformation that redefined how mammals move across the land.

The story of the kangaroo begins over 90 million years ago in North America, emerging during an era long before the rise of famous dinosaurs like the T. rex. While many early marsupial lineages perished, some migrated to South America, where they diversified into hundreds of species, including the opossums found there today. These early marsupials appeared during the same period that crocodiles and snakes first emerged. While many lineages vanished, some groups successfully adapted to new environments.

The journey to Australia was facilitated by shifting land masses and a much warmer Antarctica. Approximately 55 million years ago, a group of these ancestors crossed a land bridge from South America into Australia before the southern continents separated. Once they arrived on the Australian continent, they began to branch out into various groups, eventually leading to the roughly 250 species of marsupials that inhabit the region today. The land bridge connection occurred before the southern continents split apart. This migration allowed for significant diversification into various species.

The specific lineage of kangaroos began to emerge about 15 million years ago. Their ancestors were not ground-dwelling giants but rather opossum-like creatures that lived in trees. As the environment shifted and grasslands expanded, these animals moved from the canopy to the earth, adapting their skeletal structures for terrestrial life. Many different types of these marsupial species eventually died out over time. They underwent a radical transformation as they transitioned to life on the ground.

The modern red kangaroo we recognize today is a relatively recent development, having evolved from other kangaroo species about 3 million years ago. This evolutionary trajectory highlights a unique biological pivot: moving from arboreal lifestyles to specialized bipedal movement in response to changing landscapes. The red kangaroo is one of about 50 distinct kangaroo species found in Australia today.

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