Sahul - Pleistocene Continent of Australia, Tasmania and New Guinea

What Did Australia Look Like When the First People Arrived?

Indonesia, North Maluku, Halmahera, island in the Pacific Ocean.'
Indonesia, North Maluku, Halmahera, island in the Pacific Ocean, on the northern route to Sahul. tropicalpix / Getty Images

Sahul is the name given to the single Pleistocene-era continent which connected Australia with New Guinea and Tasmania. At the time, the sea level was as much as 150 meters (490 feet) lower than it is today; rising sea levels created the separate landmasses we recognize. When Sahul was a single continent, many of the islands of Indonesia were joined to the South East Asian mainland in another Pleistocene era continent called "Sunda".

It is important to remember that what we have today is an unusual configuration. Since the beginning of the Pleistocene, Sahul was almost always a single continent, except during those short periods between glacial expansions when the sea level rises to isolate these components into north and south Sahul. The north Sahul consists of the island of New Guinea; the southern part is Australia including Tasmania.

Wallace's Line

The Sunda landmass of southeast Asia was separated from Sahul by 90 kilometers (55 miles) of water, which was a significant biogeographical boundary first recognized in the mid 19th century by Alfred Russell Wallace and known as "Wallace's Line". Because of the gap, except for birds, Asian and Australian fauna evolved separately: Asia include placental mammals such as primates, carnivores, elephants and hoofed ungulates; while Sahul has marsupials like kangaroos and koalas.

Elements of Asian flora did make it across Wallace's line; but the closest evidence for either hominins or Old World mammals is on the island of Flores, where Stegadon elephants and perhaps pre-sapiens humans H. floresiensis has been found.

Routes of Entry

There is a general consensus that Sahul's first human colonizers were anatomically and behaviorally modern humans: they had to know how to sail.

There are two likely routes of entry, the northern-most through the Indonesia Moluccan archipelago to New Guinea, and the second a more southern route through the Flores chain to Timor and then to Northern Australia. The northern route had two sailing advantages: you could see the target landfall on all legs of the journey, and you could return to the departure point using the winds and currents of the day.

Seacraft using the southern route could cross Wallace's boundary during the summer monsoon, but sailors could not consistently see a target landmasses, and the currents were such that they could not turn around and go back. The earliest coastal site in New Guinea is at its extreme eastern end, an open site on the uplifted coral terraces, which has yielded dates of 40,000 years or older for large tanged and waisted flakes axes.

So When Did People Get to Sahul?

Archaeologists mostly fall into two major camps concerning the initial human occupation of Sahul, the first of which suggests that the first occupation occurred between 45,000 and 47,000 years ago. A second group supports the initial settlement site dates between 50,000-70,000 years ago, based on evidence using uranium series, luminescence and electron spin resonance dating.

Although there are some who argue for a much older settlement, the distribution of anatomically and behaviorally modern humans leaving Africa using the Southern Dispersal Route could not have reached Sahul much before 75,000 years ago.

All of the ecological zones of Sahul were definitely occupied by 40,000 years ago, but how much earlier the land was occupied is debated. The data below was collected from Denham, Fullager and Head.

  • Wet tropical rainforests in eastern New Guinea (Huon, Buang Merabak)
  • Savanna/grasslands of subtropical northwestern Australia (Carpenter's Gap, Riwi)
  • Monsoonal tropical forests of northwestern Australia (Nauwalabila, Malakanunja II)
  • Temperate southwestern Australia (Devils Lair)
  • Semi-arid regions of interior, southeastern Australia (Lake Mungo)

Megafaunal Extinctions

Today, Sahul has no native terrestrial animal larger than about 40 kilograms (100 pounds), but for most of the Pleistocene, it supported diverse large vertebrates weighing up to three metric tons (about 8,000 pounds).

Ancient extinct megafaunal varieties in Sahul include a giant kangaroo (Procoptodon goliah), a giant bird (Genyornis newtoni), and a marsupial lion (Thylacoleo carnifex).

As with other megafaunal extinctions, the theories about what happened to them include overkill, climate change, and human-set fires. One recent series of studies (cited in Johnson) suggests that the extinctions were concentrated between 50,000-40,000 years ago on mainland Australia and slightly later in Tasmania. However, also as with other megafaunal extinction studies, the evidence also shows a staggered extinction, with some as early as 400,000 years ago and the most recent about 20,000. The most likely is that extinction happened at different reasons for different times.

Sources

This article is part of the About.com guide to Settlement of Australia, and part of the Dictionary of Archaeology

Allen J, and Lilley I. 2015. Archaeology of Australia and New Guinea. In: Wright JD, editor. International Encyclopedia of the Social & Behavioral Sciences (Second Edition). Oxford: Elsevier. p 229-233.

Davidson I. 2013. Peopling the last new worlds: The first colonisation of Sahul and the Americas. Quaternary International 285(0):1-29.

Denham T, Fullagar R, and Head L. 2009. Plant exploitation on Sahul: From colonisation to the emergence of regional specialisation during the Holocene. Quaternary International 202(1-2):29-40.

Dennell RW, Louys J, O'Regan HJ, and Wilkinson DM. 2014. The origins and persistence of Homo floresiensis on Flores: biogeographical and ecological perspectives.

Quaternary Science Reviews 96(0):98-107.

Johnson CN, Alroy J, Beeton NJ, Bird MI, Brook BW, Cooper A, Gillespie R, Herrando-Pérez S, Jacobs Z, Miller GH et al. 2016. What caused extinction of the Pleistocene megafauna of Sahul? Proceedings of the Royal Society B: Biological Sciences 283(1824):20152399.

Moodley Y, Linz B, Yamaoka Y, Windsor HM, Breurec S, Wu J-Y, Maady A, Bernhöft S, Thiberge J-M, Phuanukoonnon S et al. 2009. The Peopling of the Pacific from a Bacterial Perspective. Science 323(23):527-530.

Summerhayes GR, Field JH, Shaw B, and Gaffney D. 2016. The archaeology of forest exploitation and change in the tropics during the Pleistocene: The case of Northern Sahul (Pleistocene New Guinea). Quaternary International in press.

Vannieuwenhuyse D, O'Connor S, and Balme J. 2016. Settling in Sahul: Investigating environmental and human history interactions through micromorphological analyses in tropical semi-arid north-west Australia. Journal of Archaeological Science in press.

Wroe S, Field JH, Archer M, Grayson DK, Price GJ, Louys J, Faith JT, Webb GE, Davidson I, and Mooney SD. 2013. Climate change frames debate over the extinction of megafauna in Sahul (Pleistocene Australia-New Guinea). Proceedings of the National Academy of Sciences 110(22):8777-8781.

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Hirst, K. Kris. "Sahul - Pleistocene Continent of Australia, Tasmania and New Guinea." ThoughtCo, Sep. 27, 2017, thoughtco.com/sahul-pleistocene-continent-172704. Hirst, K. Kris. (2017, September 27). Sahul - Pleistocene Continent of Australia, Tasmania and New Guinea. Retrieved from https://www.thoughtco.com/sahul-pleistocene-continent-172704 Hirst, K. Kris. "Sahul - Pleistocene Continent of Australia, Tasmania and New Guinea." ThoughtCo. https://www.thoughtco.com/sahul-pleistocene-continent-172704 (accessed November 23, 2017).