The dingo: a post-domestic wild animal?

Long-term readers of my blog will be familiar with my dedomestication hypothesis that I proposed in the dedomestication series. The term dedomestication is not very established in scientific literature yet, but there can be now doubt that natural selection will change domestic animals that have returned into the wild. This evolutionary process would result in what I call a post-domestic wildtype, opposed to a predomestic wildtype. This post-domestic wildtype would be just as wild as any other wild animal, with the difference that it descends from a domestic population. 

I proposed that this post-domestic wildtype is not necessarily a revert to the original predomestic wildtype, but that it depends on the selective pressures in the respective environment, genetic drift and also that novel traits can be beneficial, especially in a new environment. As I write in my dedomestication series, the hypothesis has empirical problems. For once, feral domestic animals are understudied in terms of possible evolutionary changes they experience. And moreover, there are hardly any feral domestic populations that have been living in the wild under natural selection for a considerable time span sufficient for evolutionary changes to become visible and at the same time reproductively isolated from backcrossing with wild or domestic animals. For example, feral pigs in North America (razorbacks) sometimes greatly resemble the Eurasian wild boar, what would endorse one of the main proposals of the dedomestication hypothesis (namely that wildtype traits tend to have a higher evolutionary fitness and thus the feral population starts to resemble the original wildtype on adaptive traits). The problem is, however, that these feral pigs often hybridized with wild boar that have been introduced there as well, what explains the resemblance between the two. 

Nevertheless, I see two possible candidates for a post-domestic wildtype because of a considerable time span they have been reproductively isolated and exposed to natural selection: the dingo and the European mufflon. This post is going to focus on the dingo. But first of all, it is essential to define which criteria an animal would have to fit if it was to be considered a post-domestic wildtype. 

 

A definition of the post-domestic wildtype

 

The most abstract definition of a post-domestic wild animal would be that its biology is entirely shaped by natural selection and not artificial selection. In detail, this would mean: 

- It is devoid of typical signs of domestication: paedomorphy in behaviour and morphology, earlier maturity, loss of seasonal adaptions, white spotted patterns in the colour or other detrimental colour mutations, reduced brain volume, reduced sexual dimorphism

- It is adapted to the biotic and abiotic factors of its environment 

- It is more or less homogeneous in its biology, especially regarding adaptive characters 

The exact time span of how long the animal has been subject to natural selection is technically of limited relevance, because the speed at which evolutionary changes become evident depends on how genetically diverse the starting gene pool is – this is known as Fisher’s fundamental theorem and it describes that changes in allele frequency occur faster in a very diverse population compared to one that is genetically homogeneous.

 

Is the dingo a dog at all and does it have domestic ancestry? 

 

A question which has to be investigated before is if it is true at all that the dingo has a domestic ancestry and if it is a dog at all. That question is relevant as there are some sources questioning the status of the dingo as a dog and prefer to regard it as a separate wild canid species that was never domesticated like coyotes and golden jackals. 

This idea, however, seems to be contradicted by the genetic evidence. Jackson et al. 2019 have reviewed several phylogenies based on genetic analyses and all of them have the dingo placed within the phylogenetic tree of the dog [1]. This strongly implies that the ancestors of the dingo were domestic dogs. One recent study from 2022 had the dingo as a sister group to all other dog breeds examined, but the number of dog breeds used was only six [2], therefore very low considering that there are hundreds of dog breeds. It was found that the dingo has only one copy of the AMY2B gene, which is multiplied in other dog breeds as an adaption to starch-rich diet [2]. That is, however, not an argument in favour of the idea that the dingo is a never domesticated wild canid, it just means that the duplication of the gene did not occur right at the beginning of dog domestication so that there are breeds that do not have it. That would be like claiming Sayaguesa cannot be domestic because it has the E⁺ allele, which is wildtype. The dog breeds that group with the dingo are, among others, the Chow Chow, the Akita, the Basenji and Indonesian and various Southeast Asian dogs [1,3]. Half of the dingoes tested in one study have the A29 mitochondrial haplotype (which is considered ancestral to all the other mitochondrial dingo haplotypes), which is also found in East Asian, Southeast Asian and American dogs as well as the New Guinea singing dog [4]. So from a genetic perspective, there can be no question that the dingo is a dog and shares domestic ancestors with other dogs. 

It is also morphological evidence that contradicts the idea that the dingo is a distinct, never domesticated wild canid species. Dingoes do have vestiges of domestication, including typically domestic traits such as a brain volume reduced by 30% compared to the grey wolf [5], reduced mimics and less social differentiation compared to the grey wolf [5,6], curly tails in some individuals [7] and cranial paedomorphy [8] and the males are able to reproduce all the year round [7]. Moreover, some dingoes have clearly domestic coat colour variants, such as brindle or white-spotted or piebald patterns. All these traits strongly suggest that the dingo is a dog, sharing domestic ancestors with other dog breeds. 

Also the behaviour of the dingo demonstrates that it is a dog – dingoes are sometimes kept as pet dogs, and already the Australian aboriginal people kept dingoes [9]. Alfred Brehm in Brehm’s Tierleben reported that there were dingoes kept as pet dogs and were used to protect livestock. Also, ethologist Eberhart Trumler studied dingoes kept as pet dogs and reported that they can even be made house-trained. Keeping a wild canine, be it a wolf, a coyote or jackal, as a pet dog this way would be impossible. 

Therefore, putting everything together, I think there is no reason to not assume that the dingo is a dog and shares domestic ancestors with other dog breeds. 

 

Does the dingo fit the definition of post-domestic? Is it wild or feral? 

 

My definition of post-domestic can be seen above, it has three key points. Without question the dingo is adapted to its Australian environment, it can make use of various food sources and it is adapted to the climate as the wide geographic range on the continent demonstrates. Concerning its morphology, the dingo seems to be uniform like a wild animal. Concerning its colours, they are more variable than what is commonly expected. A 2021 study found that because of the variation in the dingo’s coat colour, this parameter cannot be used to discern pure dingoes from hybrids with other, later arrived feral dogs [10]. Wild animals are usually – usually, not always – comparably uniform in colour across the species and the dingo coat colour variation is obviously a vestige of domestication. However, if the domestic coat colour variants found in the dingo (I consider all of the colours found in the dingo domestic, i.e. they arose after domestication, as none of them are the wildtype colours shared by wolves, the ancestors of dogs) turn out to be adaptive in the new environment they have been introduced to (Australia), they cannot be used as an argument against a possible wild status. If a novel trait that arose during domestication is adaptive in a new environment and becomes fixed, it would actually be in line with my dedomestication hypothesis. I never proposed that a feral domestic animal would fully revert to the original wildtype under natural selection, because some novel traits can be adaptive especially when the population lives in a new environment that is different from that of the original wildtype. In Australia, the colour of the dingo is likely better camouflage than that of the wolf in Asia where the dog was domesticated. Therefore, the colour of the dingo is likely adaptive. Perhaps some more millennia of dedomestication will eventually lead to a uniform colour, via stabilizing selection and genetic drift. Therefore, if a possible post-domestic animal has retained novel traits that arose during domestication, it still can fit the criteria for being a post-domestic wild animal as long as these novel traits are either adaptive or evolutionary neutral. But the dingo also has other remnant traits of its domestic ancestry as outlined above, some of which are part of the universal “domestication syndrome” and possibly maladaptive, including the reduced brain volume, cranial paedomorphy and curly tails in some individuals. Also, the fact that dingo males are able to reproduce all year round shows that they have not yet fully redeveloped a seasonal reproduction circle. Moreover, the fact that dingoes can be used and trained as pet dogs shows that the neurologic-endocrinologic modifications that turned dogs into domestic animals are still present in the dingo, and that it has not yet lost the potential to develop domestic behaviour. To me, this suggests that the dingo should not be considered a post-domestic wild animal. 

It is problematic, however, to draw a distinctive line between feral and post-domestic wild. Rather it should be regarded as a continuum, as a spectrum. The dingo definitely is on this spectrum, but in my opinion still closer to feral than to post-domestic wild. Interestingly, there also seems to be a continuum from other basal dogs to the dingo, as Southeast Asian pariah dogs, Borneo dogs, the Korean Jindu and the American Carolina dog are phenotypically very similar to dingoes. All of them, including the dingo, can be kept as pets. 

 

An upcoming post is going to focus on the European mufflon as a post-domestic wild animal candidate.

 

Literature

 

[1] Jackson et al.: The Dogma of Dingoes – Taxonomic status of the dingo: A reply to Smith et al.. 2019.

[2] Field et al.: The Australian dingo is an early offshoot of modern breed dogs. 2022.

[3] Larson et al.: Rethinking dog domestication by integrating genetics, archeology, and biogeography. 2012. 

[4] Savolainen et al.: A detailed picture of the origin of the Australian dingo, obtained from the study of mitochondrial DNA. 2004. 

[5] Hemmer: Domestikation, Verarmung der Merkwelt. 1983 

[6] Trumler: Ein Hund wird geboren: der Ratgeber für den Hundefreund. 1982. 

[7] Zimen: Der Hund – Abstammung – Verhalten – Mensch und Hund. 1988. 

[8] Smith et al.: Brain size/body weight in the dingo (Canis dingo): comparisons with domestic and wild canids. 2017. 

[9] Roland Breckwoldt: The dingo: still a very elegant animal. In: A symposium on the dingo. 2001. 

[10] Cairns et al.: Pelage variation in dingoes across southeastern Australia: implications for conservation and management. 2021.