Origin of Koalas & their Evolution

According to the fossil records, Koalas have been living on earth for about 30 million years (some also quote 25 million years too). Thirty million years ago, Australia was already separated from Gondwana and it had significantly drifted away from it. Therefore; we can also safely assume that koalas have been living on the continent of Australia for 30 million years as well. However; even within these 30 million years different genera of koala had existed and thrived over the years.

Koalas have been living on earth at the Australian continent for almost 30 million years. However; modern koalas only arose 4.5 to 2 million years ago from the Phascolarctos genera.

These genera included Litokoala, Madakoala, Perikoala, Koobor and Phascolarctos. Today's koalas belong to Phascolarctos genera and is believed to be in its current from the last 4.5 to 2 million years. Therefore; the modern-day koalas in their current form is living on earth from the last 4.5 to 2 million years while the overall koala family species arose some 30 million years ago.

It is also believed that koalas 30 million years ago koalas had a different lifestyle and they used to live in rainforests. They had a diversified diet and were not only relying on the Eucalyptus leaves as part of their diet. However; about 15 million years ago Australia was suffering from the frosty drought which led to the emergence of the drought tolerant plantation such as the Eucalyptus trees. Koalas at that time desperately adapted to the Eucalyptus trees and today's koala species are the continuity of such koalas.

Today's Eucalyptus eating koalas are the continuity of the koala group which adopted to the Eucalyptus trees about 15 million years ago.

At the same time some other relatives of koala family demised while the modern day's Eucalyptus eating koala thrived and increased in numbers. Therefore; the rise of the Eucalyptus plantation during the frosty drought in Australia also led to the rise of the modern-day koalas at the Australian continent.

But what about the koalas' presence beyond 30 million years ago? Did they have any relatives at that time? It is speculated that beyond 30 million years ago, koalas only had their ancestors roaming freely at the Australian continent. At that time koalas were literally not koalas but some other animal which had a core preference to feed from grasslands as well as trees. In fact; these ancestors were the ones which separated from the wombat ancestors about 42 million years ago.

Before 30 million years and after 42 million years ago, koalas' ancestors named as Diprotodonts used to roam across the continent of Australia. They were huge in size and weighed almost two ton.

The koala ancestors which separated from wombats are classified as Diprotodonta. Diprotodonts were huge animals with two big front teeth and they weighed almost two tons. Therefore; in between 30 million years and 42 million years ago, koalas were in fact Diprotodonts with a huge appetite. These arguments indicate that koalas were living 42 million years ago as Diprotodonts.

Today; wombats are the only closest relatives of koalas across the continent of Australia. Both wombats and koalas are thought to be a single animal beyond 42 million years ago from which the koalas' ancestors and wombats' ancestors evolved. Furthermore; it was the common ancestor of koalas and wombats which entered the Australian continent about 55 million years ago from the South America.

Beyond 42 million years ago, koala and wombat had a common ancestor. Its size is not known but it is believed that their common ancestor was a burrower living underground with a keen motivation to climb trees for food.

Therefore; this ancestor would have played a fundamental role to derive marsupials at the Australian continent too. The koala and wombat's common ancestor was believed to be a borrower who used to live underground but also had a motivation to climb trees as well.