Australia on fire

By Razib Khan | October 13, 2011 8:22 pm

Fascinating, Orbital cycles, Australian lake levels, and the arrival of aborigines:

But the other big feature is that the lake-filling events that occurred after 50,000 years ago were much smaller than those which occurred before. Climactically, the conditions 10,000 years ago should have been the same as the conditions 115,000 years ago. But the lake was only a fraction of the size. The authors find no natural causes which can explain this. So they suggest that the aridity starting around 50,000 years ago is related to the reduction in forest and increase in grasslands which occurred at this time. This vegetation change was a result of a huge increase in the frequency of fire in central Australia, which allowed fire-adapted plants to prosper at the expense of moisture-retaining forest. The increase in fire at this time is generally associated with the arrival of the first people on the Australian continent. It is known that of Australia’s megafauna went extinct at this time, but Magee et al. (2004) show that even the tropical rains were effected by human migration, with drastic changes to the continent’s largest river basin.

If you read some of the academic literature on fire ecology you have a hard time not coming to the conclusion that modern humans terraformed the planet Earth! The hallmark of modern H. sapiens seems to be extinction of large organisms, a propensity to go where no hominin has gone before, and copious utilization of the “red flower.”

MORE ABOUT: Anthropology
  • Sandgroper

    Thanks LL.

  • ohwilleke

    FWIW, intentional use of fire is an invention that dates to H. Erectus.

  • Razib Khan

    #2, well, there’s a touch of debate about that. i’d put the h. erectus use of fire at 0.75 probability. u?

  • blindboy

    Aboriginal fire may have caused the ecosystems involved to reach some kind of tipping point but given the nature of the soils, the climate trends and the type of fire prone vegetation that by that time dominated the forests, they may only have hastened the inevitable. The data presented here is less than totally convincing.

  • Sandgroper

    “they may only have hastened the inevitable”

    So what? I think you have missed the point, which is about pegging the time of human arrival, which turns out to be very important. No one cares about whether extincting megafauna was naughty or not – it’s an idiotic point.

  • Blackbird

    Guns, germs, steel and fire then?

  • Justin Giancola

    In my environmental science class we recently watched a video in which a scientist quartered off a small bit of land in some desert and removed all the Kangaroo Rats. The desert rather quickly converted into grassland and other animals stopped showing up and new animals started coming in. They deemed the Kangaroo Rat a “keystone species” or something to that effect.

    Being that Australia never had hominids at all – or seemingly top predators? – and had a very delicate balance with regards to animals that had already gone extinct elsewhere and their unique descendants, humans showing up may not have even had to do anything drastic themselves like set fires or over kill animals. They may have just tipped a scale that set a very delicate ecosystem out of wack and this had an affect on the wildfire cycle.

    Even if this is rudimentary for some of you I think it’s an important point to make – some people may take on this Mr. Mackey-esque: h-humans are bad mmkay. :)

  • pconroy


    What about the Thylacine, the so called “Marsupial Wolf”, wouldn’t that have been an apex predator?

  • Justin Giancola

    Oh I really was asking – while repeating something I had heard like no big cats and wolves and what not past the Wallace Line – but that is very cool!

  • Brian Too

    Tangentially, I seem to remember some experiments involving elephants in Africa. They found that if you excluded elephants from an area of veldt, grassland species declined and trees increased sharply.

    Mankind is not the only shaper of the land. Also relevant in relation to the extirpation of Australian megafauna.

  • blindboy

    Sandgroper the piece clearly links the ecological change to the increase in fire frequency which they infer is a direct result of human arrival. My point is that this is only an inference. The drying out of Australia had been in process over a long period of time. We know from the palaeoclimatic record that changes can happen rapidly. Human arrival may have caused a tipping point but the tipping point may have happened anyway so the data is at best only weak evidence of (a) human arrival time and even weaker evidence for (b) humans causing the change.
    The fact that they cannot identify a natural cause means only that, it does not mean there was no natural cause.

    This is not say that the hypothesis is wrong there is plenty of other evidence for the vegetation changes at that time but being a bit of a skeptic I won’t be jumping to any conclusions about it’s cause.

  • clark

    Completely ignorant of all this stuff. Thanks for the post Razib. I wonder about the adaptivity of humans to these new environments versus the previous environments as humans move into an area. That is does the destruction by humans (planned or not) help or hinder humans or do the humans simply becomes what works in that environment. It certainly seems some environments are more conducive to reasonable populations of humans than others. (To take an extreme examples compare densities in tundra areas verses more moderate zones)

    If there is such a link then that would provide yet an other “economic incentive” for humans with such capabilities to spread out successfully.

    Brian (10), oddly while I’ve not read about this and humans (other than in modern times) I have read about this with respect to wildlife. For example I know of several areas fenced in now to exclude deer with massive increases of bio-diversity. So the phenomena certainly isn’t limited to humans in the least.

    It’s an interesting question since it suggests that a subtle change can lead to significant changes in both diversity but also relative success of various species. (OK, something I guess everyone already knew – but it’s kind of like in mathematics where you find Pi or e popping up over and over again – it’s always interesting in each context)

  • Sandgroper

    #9 – If you think Thylacine was cool, check out this furry pet:

    No big cats and wolves, but parallel evolution provided some apex marsupial predators that bore some remarkable similarities to the placental mammal equivalents.

    And if you think Komodo Dragons are neat, have a look at this:

    #11 – Fine. So, being not totally convinced, what conclusion have you not jumped to about extinctions in Tasmania? Or does your lack of total conviction prevent you from joining dots and constructing hypotheses that fit the data?

  • Eurasian Sensation

    @ Justin:

    There are three realistic candidates for “apex predator” in Pleistocene Australia.

    – The thylacine or Tasmanian Tiger
    – Thylacoleo, the “Marsupial Lion”
    – Megalania, a 6 metre long monitor lizard.

  • Sandgroper

    #3 – Well, I’ll give you an answer. I would put it close to 1 because I read a lengthy paper Greg Laden had written on the use of roots and tubers as food sources which needed to be cooked to be digestible, plus the energy requirements for increasing brain size.

    The earliest estimate I have seen is 1.5 billion years from archaeological sources, but that’s a tricky business of course.

  • TGGP

    “even the tropical rains were effected by human migration”
    Shouldn’t that be “affected”?

    Sandgroper, that sounds like Wrangham’s theory in “Catching Fire”.

  • ackbark

    Setting fires to wipe out groups of megalania might have seemed highly practical 40,000 years ago.

  • Razib Khan

    #17, barbecue?

  • Sandgroper

    #16 – Yes. From memory, Greg Laden expanded on that by discussing the types of foods that required heat treatment to make them digestible – roots, tubers etc. Greg is good on that stuff, if only he would do more of it and less of the other.

    #17 – It doesn’t sound like a bad idea now. An ambush hunter that’s 20 feet long and possibly venomous? Yeesh.

  • Justin Giancola

    13. gotta love parallel evolution!

    and I’ve had kangaroo before and it was good; I don’t think you guys would be amiss to try your hand at bbqing it.

  • Sandgroper

    It’s probably too low in fat for barbecuing, it would come out too dry. It’s best fried or stewed. Or thrown whole on the fire until the fur is singed off :)

  • Sandgroper

    But while you mention it, and it’s a bit of a trivial point, it’s worth noting not all Australian megafauna went extinct. The red kangaroo is a prime example of megafauna that is still with us today, and doing very well, thank you.


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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at


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