Australasian Science: Australia's authority on science since 1938

Australia’s First Dingo

dingo

The low genetic diversity observed in dingoes indicates that present-day populations might be derived from an isolated colonisation event that involved just a single pregnant female. Credit: Sam Fraser-Smith/Wikimedia Commons

By Joanne Wright & David Lambert

Genetic analyses suggest that in a single colonising event the dingo reached Australia during the Holocene. Since rising seas had already inundated the land bridge connecting Australia to South-East Asia, the dingo must have been accompanying an ancient human sailor.

Australia has some of the earliest evidence of human habitation outside Africa, with initial settlement dated between 40,000 and 60,000 years ago. Much of our knowledge of the prehistory of Australia’s first people, the Aboriginal Australians, comes from archaeological remnants such as tools, shell middens, rock art, and the remains of the people themselves.

The Holocene, which encompasses the period from approximately 12,000 years ago to the present, was a period of major environmental change in Australia. Until that time, Australia, New Guinea and Tasmania were connected, and comprised a single continent known as Sahul.

An increase in temperature caused a post-glacial rise in sea levels, and this geographic continuity became interrupted. Approximately 12,000 years ago Australia and Tasmania became separated, and 8000 years ago the isthmus connecting New Guinea and Australia became submerged.

Between 6000 and 3000 years ago, there is evidence of sudden major cultural change occurring in Australia. Described by many as a mid-Holocene “intensification”, during this period a number of new innovations and technologies appeared suddenly in the archaeological record after an extended period of little change.

During the Pleistocene, the stone tool kit used by Aboriginal Australians consisted of very basic flaked stone implements. However, it appears the tool kit changed very rapidly about 5000 years ago, with more varied and refined tools being made. Over this period these tools were widely used across the mainland – there is no evidence that they reached Tasmania.

In addition to new stone tools, Aboriginal Australian languages appeared to expand during this period, becoming more complex. Aboriginal Australian languages are classified into two major groups: Non-Pama-Nyungan (NPN) and Pama-Nyungan (PN).

The NPN group is extremely diverse and linguistically complex, consisting of 96 dialects from 20 different language families. It is restricted to mainly Arnhem Land in the Northern Territory and the Kimberley region of Western Australia.

In contrast, the PN group is a single language family consisting of 289 dialects covering most of the Australian mainland, including all but the eastern islands of the Torres Strait where Papuan languages are spoken.

The distribution of these language groups points to the possibility that they were introduced at different times and by separate migrating populations.

The widespread appearance of new stone tools, with no clear prototypes, and the sudden expansion of Aboriginal Australian languages raised questions about their origins. Did new migrating populations introduce these languages and tools, or did they arise locally?

These questions have generated considerable debate. Many believe that they were local adaptations, and cite putative environmental pressure as a possible driver. It is thought that around 4500–5000 years ago a dominant Walker Circulation (which controls ocean currents and trade winds) and an El-Niño Southern Oscillation (an increase in ocean temperatures) commenced, bringing decreased rainfall and severe droughts to many parts of Australia.

With environments changing dramatically, the probability of being unsuccessful when hunting or acquiring food may have increased, leading to the need to develop new technologies in order to thrive. However, the sudden appearance of the dingo in the Holocene cannot be explained as either a local invention or the result of environmental change.

For many decades it was assumed that the dingo, Canis lupus dingo, had been introduced to Australia some time in the Pleistocene during the initial colonisation of the continent. Today, in light of archaeological evidence, it now appears that the dingo’s introduction occurred much more recently. As there is no archaeological record of dingo remains in Tasmania, and given that Tasmania was cut off from mainland Australia by rising sea levels ~12,000 years ago, this dates the dingo’s arrival more recently.

When and how the dingo arrived in Australia is unknown, but it is widely accepted by archaeologists that the dingo came during the mid-Holocene intensification.

The earliest undisputed age of dingo remains is from Madura Cave on the Nullarbor Plain in Western Australia. These were radiocarbon dated to 3450 ± 95 years ago. Dingo remains at other locations across the Australian continent also date to approximately this same period. These finds include remains from Wombah Midden on the north coast of New South Wales (3230 ± 100 years), Fromm’s Landing No.6 in the lower Murray River in South Australia (3000 ± 91 years) and Balmoral Beach in Sydney (<3310 ± 50 years).

Commensalism between Humans and Animals

In ecology, commensalism is the relationship between two organisms whereby one benefits and the other remains unaffected. The commensal (the beneficiary) obtains food, shelter, transport or support from the host species (the unaffected). An example of commensalism is the interaction between cattle egrets and grazing cattle: when cattle graze, their movements through the paddock disturb insects in the grass, which becomes a food source for the commensal egrets.

There is extensive evidence of commensality between ancient humans and other animals, and these relationships have been used to reconstruct paths of human migration. These associations are thought to have contributed to the eventual domestication of animals.

Previous research into human commensal relationships has included genetic analyses of Pacific rats that enabled Prof Lisa Matisoo-Smith of Otago University to date and trace the migration of Polynesian seafarers – the ancestors of New Zealand’s Māori. Models such as this have allowed us to learn more about human interaction and to detect ancient migratory paths, aspects of human prehistory that may not be detected through analyses of the DNA of ancient human remains alone.

However, choosing a commensal species for this purpose is not without its difficulties. It is important to choose a species that is unable to disperse independently outside of its natural range. The animals should not be able to migrate from one island to another unless accompanied by humans. This allows us to track the movements of humans by investigating the commensal’s own evolutionary history.

Thus the Oceania region, encompassing the Pacific Islands and Australia, is ideal for tracing paths of human migration using commensal animals, and the dingo is an excellent candidate as a commensal animal to enable us to learn more about human migration to Australia during the Holocene.

What Do We Already Know?

Before the use of DNA to establish a genetic history, morphological analysis of skeletal remains was the norm. This involved comparing the skull shape and size of the dingo with those of a large number of other breeds of dog. These studies indicated a strong resemblance between the dingo and wild dogs that came from India or Asia, in particular the Indian pariah street dog and the wild dogs of South-East Asia.

More recently molecular technology has allowed hypotheses about the origin of the dingo to be tested in more depth. While there have been a number of studies of dingo DNA, mainly involving short regions of the genome, the origin of the dingo is yet to be resolved.

Early studies of present-day dingoes indicated that their genetic diversity is much lower than domestic dogs. One mitochondrial study that focused on DNA passed from mothers to offspring discovered that 83% of dingoes sampled carried the same mitochondrial type, with all other haplotypes being separated by very small differences.

The low genetic diversity observed in dingoes indicates that present-day populations are likely to be derived from an isolated colonisation event, theoretically one that involved just a single pregnant female. If more than one introduction occurred in the past we would likely observe a number of different mitochondrial haplotypes. However, this is not the case.

What previous studies have shown is that the dingo belongs to a group of very old Asiatic breeds that include the New Guinea singing dog, basenji, Siberian husky, Alaskan malamute, chow chow and Japanese akita. These “ancient” breeds were closer genetically to wolves than to other dog breeds.

All genetic studies of the dingo to date have relied on DNA obtained from contemporary dingo populations. It is unclear if there are any “pure” wild dingoes remaining in Australia, and it has been suggested that dingo–dog hybridisation rates exceed 80%. Hence it is difficult to assess how much of the genomic data reported to date belong to dingoes rather than wild domestic dogs.

One way to limit this problem would be to extract DNA from archaeological material pre-dating European settlement, a time in which there were no domestic dogs for the dingo to mate with. This would ensure that the most authentic dingo sequences are obtained.

What we can be sure of is that the dingo would have needed to cross at least 50 km of open seas to reach Australia’s shores from its closest neighbour between 3545 and 12,000 years ago. It is highly unlikely the dingo made such a journey un­assisted.

It has been speculated that traders from mainland Asia transported the dingo to Australia by canoe, as a source of food or as a travel companion. What role the dingoes might have played remains unknown, but there are clear advantages to travelling with dogs. In 2002 anthropologist Paul Taçon suggested that dogs may have improved sanitation by disposing of food scraps, aided in hunting or acted as an early warning system, ultimately leading to greater chances of survival for humans.

What Can We Learn?

The question of human origins and the mapping of ancient migration is one that has long interested science. While we may never know why the dingo was brought to Australia, or what role they played in the lives of the ancient humans who transported them, by determining their origin and the timing of their arrival we may learn, by proxy, more about human migration to Australia in the Holocene. This information may be useful for corroborating evidence of gene flow detected in the DNA of ancient Aboriginal Australians.

Unravelling the mystery of the dingo and integrating these results with those from other fields such as archaeology, linguistics and genetics will be an important tool to better understand the complex prehistory of our continent.

Joanne Wright is a PhD student supervised by David Lambert, who is Professor of Evolutionary Biology at Griffith University’s Environmental Futures Research Institute.