Dingo - Origin and Genetic Status

Origin and Genetic Status

Since dingoes were the only big placental mammals in Australia, apart from humans, and looked similar to dogs under human care but lived in the wild, their origin was a subject of much speculation and debate since the 18th century and especially in the first half of the 20th century. Later archaeological and morphological studies indicated a relatively late introduction and a close relationship to other domestic dogs. The exact descent, place of origin and time of their arrival in Australia were not identified, nor whether they were domesticated or half-domesticated at the time of their arrival and therefore were feral or completely wild dogs respectively.

A widely distributed theory says that dingoes have evolved or were bred from the Canis lupus pallipes or Canis lupus arabs around 6 000–10 000 years ago (this was also assumed for all domestic dogs). This theory was based on the morphological similarities of dingo skulls and the skulls of these wolves. However genetic analyses indicated a much earlier domestication.

Analyses of amino acid sequences of the haemoglobin of a "pure" dingo in the 70s supported the theory that dingoes are more closely related to other domestic dogs than to grey wolves or coyotes. Additionally it was assumed that dingoes and other Asian domestic dogs are members of a group of domestic dogs that went feral very early. At the same time, DNA-studies on Australian dingoes and other domestic dogs were performed to differentiate between both populations in a reliable way and determine the extent of the interbreeding. At the first two examinations, during which at first 14 loci and later 5 of these loci were examined, no genetic difference could be found. Later on the analyses were expanded to 16 loci. This time dingoes from Central Australia, the Eastern Highlands, dingo-hybrids and domestic dogs of other origin were examined. The researchers were surprised that they could not find any differences no matter what kind of examination they used. It was reasoned that dingoes and other domestic dogs have a very similar gene pool. However, since also only few differences in the enzymes of different species of the genus Canis could be found, it was assumed that a lack of differences might not indicate a close taxonomical relationship. It was also reasoned that the degree of interbreeding in the wild would be hard to determine.

During analyses in the end of the 1990s researchers also analysed 14 loci and detected a significantly lower genetic variability among Australian dingoes than among other domestic dogs and a small founding population was considered. There was one locus found that might have been suitable for differentiation, but not in the case of interbreeding of a dingo-hybrid with other "pure" dingoes. Additionally it was suspected that findings of other suitable loci might be used to determine whether there are clearly separate sub-populations of the "pure" dingoes.

To determine the origin and time of arrival of Australian dingoes, mtDNA-sequences of 211 dingoes and 19 archaeological samples from pre-European Polynesia have been compared in 2004 with DNA-samples of 676 other domestic dogs and 38 grey wolves. The domestic dog samples came from China, Africa, Southwest-Asia, India, Siberia, the arctic America, Europe, Mongolia, Korea, Japan, Vietnam, Cambodia, Thailand, Indonesia, the Philippines, Malaysia, New Zealand, Hawaii and the highlands of New Guinea. The dingo-samples came from zoos, wildlife parks, dingo-conservation-groups, dingo-lovers and 192 wild living specimen from 27 areas scattered over the Australian continent, mainly from the Pilbara-region, New South Wales and the Northeast of Victoria. The wild specimen had been selected based on similarities of external appearance, to exclude the influence of dingo-hybrids and other domestic dogs as far as possible.

Compared to wolves and other domestic dogs the variation of mtDNA-sequences was very limited too. Among dingoes only 20 mtDNA-sequences differing in 2 point mutations at most could be found. In comparison: 114 mtDNA-sequences with a maximal difference of 16 point mutations between the DNA-types could be found among other domestic dogs. Two of the dingo mtDNA-types were similar to that of other domestic dogs (A9, A29), while the other 18 types were unique to dingoes. In a phylogenetic tree of wolves and domestic dogs, dingoes fell right into the main clade (A), which contained 70% of all domestic dog types. Within this clade the dingo-types formed a group around the type A29, which was surrounded by twelve less frequent dingo-types, as well as a set of other domestic dog types. This mtDNA-type was found in 53% of the dingoes and was also found among some domestic dogs from East-Asia, New-Guinea and the American Arctic. Based on these findings it was reasoned that all dingo-mtDNA-types originated in A29. A9 was only found in one individual and it was regarded as possible that this type is the result of a parallel mutation. Based on a mutation-rate of mtDNA and that A29 is the only founder–type it was regarded as most likely that dingoes arrived in Australia about 4,600 to 5,400 years ago, which was consistent with archaeological findings. However, it was also considered that dingoes might have arrived within 4,600 to 10,800 years ago, in case that the mtDNA-mutation rate was slower than assumed. Furthermore it was reasoned that these findings strongly indicate a descent of dingoes from East-Asian domestic dogs and not from Indian domestic dogs or wolves. In addition these findings indicated two possibilities of descent:

• All Australian dingoes are descended from a few domestic dogs, theoretically one pregnant female
• All Australian dingoes are descended from a group of domestic dogs, who radically lost their genetic diversity through one or several severe genetic bottlenecks on their way from the Asian continent over Southeast-Asia

Nonetheless, the existence of other mtDNA-types on the islands surrounding Australia indicate there have been other types apart from A29 and only one single founding event. These results also indicated that there hasn't been any significant introduction of other domestic dog on the Australian continent prior to the arrival of the Europeans. Also, a shared origin and some sort of genetic exchange between Australian dingoes and the New Guinea singing dogs was regarded as possible. The current state of the Australian dingoes was ascribed to the long wild existence of these dogs and assumed that they are an isolated example of early domestic dogs.

Despite accordant claims, these findings did not show that only dingo females mate with non-dingo males and not vice versa. The findings would not allow such a conclusion, since the mating of a dingo female with a non-dingo male could not be detected via analyses of mtDNA. Furthermore the researchers made sure from the start that dingo-hybrids were excluded as far as possible.