The evolution of kangaroos: Competition, continental movements and their exclusive presence in Oceania

Updated to November 16, 2023, 12:00

When we think of kangaroos, koalas, wallabies, or Tasmanian devils, our minds are instantly transported to the Australian continent and its surrounding areas. However, beyond their geographical location, these animals share a common trait: they are marsupials. This class of mammals is characterized by their incomplete development in their mother’s womb, followed by the completion of their development in their parents’ marsupial pouch.

There are currently around 270 marsupial species worldwide. The majority, 200 of them, are found in Oceania, specifically on the Australian continent. However, approximately 70 species of marsupials can also be found in America.

To answer the question of why kangaroos are only found in Oceania, we must delve into the history of these animals, mammals in general, and our planet.

Marsupials emerged during the Cretaceous period, which occurred between 145 and 65 million years ago. They appeared later than placental mammals, which have evidence dating back to the Jurassic period, between 201 and 145 million years ago.

In the past, marsupials coexisted with placental mammals in regions that now correspond to Europe, Africa, or North America before becoming extinct.

History of Planet Earth

Around 150 million years ago, the continents began to separate from a single landmass known as Pangea. The marsupials’ story continues in Gondwana, the southern supercontinent formed after the separation of Pangea. Here, marsupials had to compete with placental mammals for ecological niches in order to survive and evolve.

During this time, placental mammals with a more efficient reproductive system gradually displaced marsupials into smaller ecological niches.

Millions of years ago, Antarctica and Australia separated. Antarctica drifted towards the south pole, while Australia moved towards the equator.

Marsupials migrated from South America to Australia through Antarctica. As Antarctica drifted towards the south pole, cooling progressively, Australia moved towards warmer latitudes near the equator. Isolated from the rest of the continents, marsupials found a way to survive and thrive in Australia, while becoming extinct elsewhere.

In Australia, free from competitors, marsupials were able to occupy new ecological niches, diversify, and evolve into the iconic species we recognize today. Kangaroos, koalas, wallabies, and Tasmanian devils are just a few examples of these unique marsupials found exclusively in Australia. Who would have thought that their presence is the result of millions of years of competition and tectonic movements?