Conservation Biology

Thursday, August 03, 2006

ABORIGINAL ECOLOGICAL FOOTPRINT: BOTH PHYSICAL AND PLACENTAL?

The out of Africa Hypothesis suggests that ancient people could not have inhabited the Australian continent before 50 000 years ago [1], but in 1974, Mungo man was discovered by James Bowler of the University of Melbourne at Lake Mungo at the far Western region of New South Wales [1]. Initially scientists indicated that the remains of Mungo Man could be as old as 60 000 years old, but new evidence indicates that the skeleton is only about 40 000 years old, and that the historical people of the time could have been living there for 10 000 years [1]. Although there is a lot of variation and opinion regarding the time-line of Australian pre-history, the suggested minimum time-frame for the original arrival of people to the Australian continent is between 40 000 to 45 000 years ago [3]. There are still those who consider this date to be as much as 70 000 years ago [3].

Who are the Aborigines and what has been their impact and contribution to Australia?

The word “Aboriginal” means “earliest known,” or “native,” and was originally used in Greek and Italy to describe the original people of those areas [2]. The world’s human population was generally small 30 000 years ago, and as far as we know, there were no cultivated crops or farmed animals, nor had working with metal been discovered yet [2]. During the last great ice-age in the Pleistocene epoch [4], the continent of Australia was connected to New Guinea. The islands of Borneo and Java were a lot bigger than they are today as a result of the vast amounts of water being locked away in the polar ice sheets [2]. The distances between islands was closer and the sea-level was probably about 100 to 150 meters [3] shallower than it is today, making migration from nearby land masses easier, facilitated by some type of water craft such as a raft [2]. The migration of the Aborigines to Australia is thought to be the earliest by prehistoric humans [2]. The word Pleistocene is derived from the Greek, which means “most recent,” and lasted from 1.8 million to 12 000 years ago [4]. The Pleistocene epoch is part of what is known as the geological timescale, and is the third epoch of the Neogene period and the sixth epoch of the Cenozoic era [4]. (The word “Epoch” is a sequence in time where the oldest period of time is an Eon, which is divided into Eras, which are divided into Epochs, Periods and Stages) [5].

It is suggested that the Aborigines share a common ancestor with the people of India, and that their ancestors passed through India and East Asia through the chain of islands to Australia [7]. Interestingly the tribe that took up residence at lake Mungo more closely resembled early Africans, and, the now extinct native Tasmanians were also more “African” in physical appearance [7]. The Aborigines adapted well to various and changing climates that were associated with Australia at that time in pre-history, developing a fishing culture in the area now known as Queensland, and took advantage of the woodlands areas around Victoria and New South Wales. Tasmania would have been connected to Australia during this time, and although it had a colder climate, the Aborigines succeeded in survival here too [7].

Scientists have also indicated that stone tools used in various forms by the first Aborigines were made as an adaptation to survival to facilitate the successful invasion of the Australian continent [8, 9]. Stone tools however remained relatively unchanged for several thousand years and are thought to have been used to make other tools out of wood. One of these wooden tools includes the famous boomerang, an amusing instrument of sport and leisure for today’s modern society, but its original purpose was for hunting prey. Although two varieties are known, including the hunting boomerang and the returning boomerang, it is thought that boomerangs were created as adaptations to throwing sticks, similar to those used in Egypt for example [10]. Boomerangs are not unique to Australia. Various forms have been developed by tribes in South America as well as the ancient Egyptians [10]. The Aborigines used the hunting boomerang, a carefully balanced tool, carved by stone tools to perfection, to bring down upright-standing game like Kangaroos and large ground birds [10]. The oldest boomerang found in Australia dated back 10 000 years, though it is also possible that they were used prior to this period, since wood tools do not last as long as stone tools [10].

Aboriginal culture has not changed much through the generations and there is an almost child-like innocence about the way they still apologise to the animals [7], which they kill for food. Their culture is one of unity and respect for nature. From a cultural perspective, these people probably had a very minor, yet mutualistic relationship with their environment, although the use of fire is blindly indicated as the root-cause for the possible extinction of the ancient megafauna…

Weird animals…

Large prehistoric animals roamed much of the Australian continent during the Pleistocene epoch. Fossils have been found of what are accumulatively termed “megafauna,” the large animals including marsupials and birds and lizards [6]. Fossils were discovered in the Wellington caves, which is West of Sydney, by Major Thomas Mitchell in 1831 [6]. Many of the megafauna became extinct in the late Pleistocene epoch, and it is suggested that since the Aborigines discovered Australia during this period, they may have been responsible for their extinction [6]. Evidence suggests that the Aborigines made use of fire to flush out predators and for general protection and cooking, which includes the use of fire to roast the seeds of the various Acacia trees in the Australian bush, however, the last ice-age also brought about a period of increasing drought, which reduced vast lush plains of the Australian interior [6] to desert, and although it was drawing to a close, it could have driven the herbivorous fauna into isolated areas where they could still find enough food and water [6]. As these areas became smaller, so did their population size. It could well be argued that the use of fire was harmonious and within the respectful ideals of the Aboriginal culture, while the continent of Australia was still relatively lush and green. With the drying process associated with the last ice-age, drought and therefore a higher percentage of potential fuel for runaway fires could have lead to climactic unintentional and associated demise of habitat. Could it be possible then that the Aboriginal people were only a coincidental addition to an already ecological “recession,” where the megafauna were dying out as a result of the last ice-age? With the added pressure on dwindling numbers of large animals by the world’s most successful hunter, I believe that Man’s presence was enough to seal the fate of not only the small populations of herbivores, but also the larger carnivores, which were faced with a collapse in their food-prey resource as a result, however, he was not the base-cause of it.

Some of the megafauna that is described from fossil evidence includes the following:

1) Diprotodon, which literally means “two prominent teeth.”[6]. There were various varieties of Diprotodon, varying from the small sheep-sized species to the large Diprotodon optatum, which was the size of a rhino and weighed in at about 2000kg! This was the world’s larges marsupial [6].

2) Zygomaturus tasmanicus was similar to Diprotodon, but preferred the forest areas to the open grasslands. This beast weighed in at a healthy 300 to 500kg [6].

3) Procoptodon goliah was the largest kangaroo ever to walk or hop on the face of the Earth [6]. Procoptodon goliah belonged to the Sthenurines family, the family containing 14 now extinct forms of ancient Kangaroo [6]. Procoptodon goliah weighed up to 200kg and stood almost 2.5m tall [6]. It is thought that a broadened skull and nasal passages might have facilitated the amplification of sound in this species [6].

4) Dromornis stirtoni, of the Mihirung birds, the name given by the Aboriginal people for the giant birds which they encountered, were herbivorous and weighed in at around 500kg [6]. These giants were most likely related to the common ducks or turkeys and not necessarily related to the Emus of today [6].

5) Megalania prisca, “The Ancient Giant Butcher,” the largest lizard-predator that roamed Australia measuring up to 5.5m long and weighing up to 600kg. It is clear that Megalania prisca was a carnivore [6], but it is not known if this animal could have actually tackled and killed the large marsupials like Diprotodon [6], however, there were smaller prey items around, including man!

So why did Australia have all these weirdly unique animals in the first place?

Millions of years ago, Australia was still connected to South America and Antarctica. At this time the entire area shared the same general biodiversity of prehistoric and evolving animals. When Australia split up from South America and Antarctica, it effectively isolated the rich fauna from the other two continents, and over time and differences in adaptations to different environmental conditions, different forms of animal evolved [7]. This was the time of the development of mammals (about 120 million years ago) around the world, which included a group known as the Marsupials [7]. The Marsupials give birth prematurely, unlike other mammals, which is due to the poor development of the placenta [7]. In all other regions of the world, the evolution of the placenta in placental mammals caused the out-competition of the Marsupials, however this did not occur in Australia [7]. Without the competition of placental mammal development, Australia’s mammals continued to evolve along marsupial lines [7], ultimately ending with the giants described above. A strange group of the Marsupials, the Monotremes was a further development, which incorporated egg-laying instead of giving birth to premature young. Today there are only two species in this group known to science, the Platypus and the Echidna [7].

The invasion of the Placenta!

The long-evolved placenta-less world of the Marsupials came to an abrupt end with the arrival of humans, the most highly evolved placental mammals on Earth. The Australian world where competition of evolution within the mammal types was non-existent, now took on a drastic evolutionary face-off, and unknowingly, the first human footprint not only began with the first physical impression on the virgin beach sand, but would remain as an irreversible scar like a white-wash of common world-wide domination, slowly monopolising natures hidden experimental laboratory over time. The evolutionary clock was now running out of steam for the Marsupial kingdom. With the humans came the second most successful predator, another placental mammal, the dog, or Dingo, which is the name of the now “native” Australian wild dog.

Ironically the ecological footprint deepened with the colonisation of Australia by Europeans from 1788, when waves of colonial settlements encroached ever deeper into the interior of the continent [11]. Aborigines were treated as slaves and savages, and their way of life was not only ridiculed but also persecuted.

Ending with man…this should have a new meaning.

Conclusion:

Aborigines obliviously impacted a world devoid of advanced “alien” mammals and set in motion a discovery, but also an inevitable change in the balance of nature, not by their actions alone, rather the coincidental impact in association with the last ice-age climate change. Could burning over time just innocently have gone too far as a result? I do not believe that the Aboriginal people can be labelled as responsible for the demise of Australia’s megafauna. I do however believe that they are rather victims of their own adaptation to survive.

References

[1] BBC News [Internet] 19 February 2003: 03:46GMT [cited 2 August 18:30] Available from: http://news.bbc.co.uk/2/hi/science/nature/2776697.stm

[2] Aboriginals [Internet] [cited 2 August 18:49] Available from: http://www.apex.net.au/~mhumphry/aborigin.html

[3] Wikipedia contributors. Prehistory of Australia [Internet]. Wikipedia, The Free Encyclopedia; 2006 Aug 2, 04:26 UTC [cited 2006 Aug 2]. Available from: http://en.wikipedia.org/w/index.php?title=Prehistory_of_Australia&oldid=67180006.

[4] Wikipedia contributors. Pleistocene [Internet]. Wikipedia, The Free Encyclopedia; 2006 Jul 30, 05:12 UTC [cited 2006 Aug 2]. Available from: http://en.wikipedia.org/w/index.php?title=Pleistocene&oldid=66639213

[5] Wikipedia contributors. Geologic time scale [Internet]. Wikipedia, The Free Encyclopedia; 2006 Jul 31, 20:47 UTC [cited 2006 Aug 2]. Available from: http://en.wikipedia.org/w/index.php?title=Geologic_time_scale&oldid=66919324

[6] Museum Victoria, Prehistoric life [Internet]. [cited 2006 Aug 3: 19:27] Available from: http://www.museum.vic.gov.au/prehistoric/mammals/australia.html

[7] Ancient Land of Oz, Marsupials and the drying of Australia [Internet]. [cited 2006 Aug 3: 20:28] Available from: http://ozzyfrank.150m.com/pages/Early_Oz.htm

[8] Hiscock P. 1994. Technological Responses to Risk in Holocene Australia. Journal of World Prehistory 8(3): 267 – 292.

[9] Moore M. W. 2003. Flexibility of Stone Tool Manufacturing Methods on the Georgina River, Camooweal Queensland. Archaeology in Oceania 38(1) 23.

[10] Boomerang history [Internet]. [cited 2006 Aug 3: 22:14] Available from: http://www.rangs.co.uk/boomhistory.htm

[11] Wikipedia contributors. History of Australia (1788-1850) [Internet]. Wikipedia, The Free Encyclopedia; 2006 Aug 2, 03:57 UTC [cited 2006 Aug 3]. Available from: http://en.wikipedia.org/w/index.php?title=History_of_Australia_%281788-1850%29&oldid=67176009.

David Vaughan
Senior aquarist, Quarantine
Two Oceans Aquarium
Cape Town, South Africa
davidvaughan.b-logging.com

3 Comments:

  • Hi its me again...

    Photographs will not publish with this posting, though they are uploaded successfully. I have tried repeatedly with no success. There may be a problem with Blogger. I will keep trying.

    Cheers

    David

    By Blogger davidvaughan, at August 04, 2006 9:49 AM  

  • Hi David
    I enjoyed your take on Australia. Maybe a few more peer-reviewed articles to back your view would have been great... but who knows maybe there aint many out there?

    By Blogger Karen Marais, at August 04, 2006 6:33 PM  

  • You really like to overload our brains, don't you? Your title is confusing...you should change it to something that warns us what we're in for...

    As usual, you cover a lot of concepts, and well (with a touch of the dramatic, perhaps,but that's fine in these blog pieces). Nice job.

    Still, to echo Karen, a few more peer-reviewed sources would never be amiss...

    For my own enlightenment, if you're so inclined: why is it, do you think, that placental mammals outcompeted their marsupial cousins? And which condition do you see as ancestral to mammals as a clade - placental or marsupial?

    Cheers
    Nick

    By Blogger NcK, at August 07, 2006 6:57 PM  

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