With their round, fluffy ears, large black nose and stout bodies, Koalas are instantly recognisable and among Australia’s most iconic animals. Their evolution as a species and how they’ve adapted to Australia’s changing environment is fascinating. Let’s take a closer look at their ancient origins and the diversity of koala ancestors.

From the Beginning

Koalas are marsupials, meaning they carry their babies in a pouch while they develop. Fossil studies suggest that around 65 - 50 million years ago, koalas, wombats, kangaroos and possums split off from other marsupials, beginning their own evolutionary descent. Evidence suggests that koalas and wombats shared a common ancestor around 40 - 30 million years ago, before branching off into separate families. During the Oligocene and Miocene epochs (33.9 - 23 million years ago and 23 - 5 million years ago respectively), several koala-like species - a family group known scientifically as Phascolarctidae - existed alongside one another in lush forests. Around the size of small domestic cats, these creatures probably ate a mix of leaves, forest plants and possibly insects.

In addition to these miniature koala ancestors were Ilariids, a family of giant koala-like marsupials. These weighed up to 200kg - about the weight of an adult lion - and evolved parallel to modern koalas rather than being a direct ancestor. These too are thought to have eaten soft leaves.

Species such as Nimiokoala died out around 16 million years ago, while others - such as Madakoala - survived into the Pleistocene epoch, dying out only around 280,000 years ago. 

Evolution of Modern Koalas 

Over millions of years, key evolutionary adaptations took place which helped koalas to navigate the increasing eucalyptus landscape spreading across Australia. Early koalas evolved molar teeth suitable for grinding fibrous vegetation. Their gut also adapted to detoxify eucalyptus leaves, allowing for survival that didn’t necessarily depend on eating a diverse range of plants. 

The modern species of koala is the only remaining member of the Phascolarctidae family and began to evolve around 350,000 years ago. They are perfectly adapted to life in the trees and to a diet of eucalyptus, which is toxic to most other animals. Their slow metabolism and a highly specialised digestive system enables them to survive on various species of eucalyptus, from which they get not only their nutrients but also most of their water. 

Look at any koala book now or see koalas in the wild and you’ll typically see them resting, sleeping and eating among the safety of the eucalyptus trees that have kept them alive over millennia. 

A remarkable species

The next time you hear stories about koalas, think about their evolution and just how remarkable the modern koala really is. As well as climate shifts and habitat changes, they’ve also survived things like habitat loss through deforestation, as well as hunting which was prominent during the fur trade in the 19th and early 20th centuries.

Today, koalas remain an integral part of Australian culture and their survival is aided by conservation efforts. There are even koala picture books and theatre productions dedicated to this wonderful animal, such as The Koala Who Could which is based on the book by Rachel Bright and Jim Field. View tour dates and book your tickets today.