Drying Climate Turned Possum-Like Critter Into the Strange Koala

By Andrew Moseman | December 23, 2009 4:15 pm

koalaMillions of years ago, a koala looked more like a possum. By studying rare skulls of the famous marsupial that date between 5 and 24 million years old, a team of Australian researchers propose how it got to looking like it does today, with findings published in the Journal of Vertebrate Paleontology.

Food was one driver, they say—millions of years ago koalas ate a variety of foods. The dietary switch to an exclusive eucalypt diet seems to have occurred during the late Miocene period, some 12 to five million years ago, when a drying climate made eucalyptus the dominant forest species [Canberra Times]. As a result, they lost their snouts and developed powerful jaw muscles.

But while koalas need to adapt to the changing food supply, they also needed to stay in communication, and began to develop the low-frequency calls that today can travel half a mile. The researchers hypothesize that the ancient koalas evolved their communication system at a time when the Australian continent was drying out and the koala habitat becoming less dense. By lowering the frequency of their calls, they were able to maintain communication in the sparser forests [Wired.com]. And to hear those low-frequency calls, koalas developed a middle ear with high volume compared to other marsupials.

“The unique cranial configuration of the modern koala is therefore the result of accommodating their masticatory adaptations without compromising their auditory system,” write the researchers [Wired.com]. In other words: you put those two things together and you get today’s adorable but strange marsupial.

Related Content:
80beats: Worsening Drought Threatens Australia’s “Food Bowl”
Discoblog: Rat Risotto And Emu Chips: Thing Not To Eat in Australia
DISCOVER: One Marsupial Too Many

Image: flickr / tinyfroglet

CATEGORIZED UNDER: Living World
MORE ABOUT: Australia, evolution
  • Christina Viering

    It will be interesting to see how homosapiens evolve.

  • Angie

    We (humans) are changing all the time… Isn´t the result of koala evolution adorable and sweet? *v* merry christmas

  • james

    yeah but they had 5 -12 million years to do it in. todays animals may only have 100 years before the average temperature of the plant increases by 6 degrees.

  • Dave

    it is quite amazing what genes can do when they undergo stress. Yes James, animals do have a short window to adapt and since evolution is a one strand at a time kind of thing, it takes a while. But Some animals will adapt in that alluded time.

    But this topic isn’t about that…

  • Crispin

    James,

    Koalas survived the Younger Dryas event 11,500 years ago when the Earth warmed 15 degrees in 1 or 2 years.

    As the temperature range predicted for the next 100 years (something the climate models have failed miserably to do for even 10 years) is -2 to +6 degrees with only one claimant (NASA) standing behind the latter.

    Koalas have survived vast changes multiple times in recent millenia. I don’t think they are at risk of developing anything other than more or less fur.

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