The Paleolithic dog was a Late Pleistocene canine. They were directly associated with human hunting camps in Europe over 30,000 years ago and it is proposed that these were domesticated. They are further proposed to be either a proto-dog and the ancestor of the domestic dog or an extinct, morphologically and genetically divergent wolf population.

One authority has classified the Paleolithic dog as Canis c.f. familiaris^[1] (where c.f. is a Latin term meaning uncertain, as in Canis believed to be familiaris). Previously in 1969, a study of ancient mammoth-bone dwellings at the Mezine paleolithic site in the Chernigov region, Ukraine uncovered 3 possibly domesticated "short-faced wolves".^[2][3] The specimens were classified as Canis lupus domesticus (domesticated wolf).^[3][4]

In 2002, a study looked at 2 fossil skulls of large canids dated at 16,945 years before present (YBP) that had been found buried 2 metres and 7 metres from what was once a mammoth-bone hut at the Upper Paleolithic site of Eliseevichi-1 in the Bryansk region of central Russia, and using an accepted morphologically based definition of domestication declared them to be "Ice Age dogs".^[5] In 2009, another study looked at these 2 early dog skulls in comparison to other much earlier but morphologically similar fossil skulls that had been found across Europe and concluded that the earlier specimens were "Paleolithic dogs", which were morphologically and genetically distinct from Pleistocene wolves that lived in Europe at that time.^[6]

The Paleolithic dog was smaller than the Pleistocene wolf (Canis c.f. lupus)^[1] and the extant grey wolf (Canis lupus), with a skull size that indicates a dog similar in size to the modern large dog breeds. The Paleolithic dog had a mean body mass of 36–37 kg (79–82 lb) compared to Pleistocene wolf 42–44 kg (93–97 lb) and recent European wolf 41–42 kg (90–93 lb).^[6]

The earliest sign of domestication in dogs was thought to be the neotenization of skull morphology^[7][8][9] and the shortening of snout length. This leads to tooth crowding, a reduction in tooth size and the number of teeth,^[7][10] which has been attributed to the strong selection for reduced aggression.^[7][8]

Compared with the Pleistocene and modern wolves, the Paleolithic dog had a shorter skull length, a shorter viscerocranium (face) length, and a wider snout.^[6] It had a wider palate and wider braincase,^[6][9] relatively short and massive jaws, and a shorter carnassial length but these were larger than the modern dog and closer to those of the wolf. The mandible of the Paleolithic dog was more massive compared to the elongated mandible of the wolves and had more crowded premolars, and a hook-like extension in the caudal border of the coronoid process of the mandible. The snout width was greater than those of both the Pleistocene and modern wolves, and implies well-developed carnassials driven by powerful jaws. In two morphometric analyses, the nearest dog skull-shape that was similar to the Paleolithic dog was that of the Central Asian Shepherd Dog.^[6]

In 2015, a study of bone collagen taken from a number of species found at the 30,000 YBP mammoth-hut site of Predmosti in the Czech Republic indicated that the Pleistocene wolf ate horse and possibly mammoth, the Paleolithic dog ate reindeer and muskox, and the humans ate specifically mammoth. The study proposes that the Paleolithic dog's diet had been artificially restricted because it was not a diet similar to the Pleistocene wolf. Some remote Arctic tribal people today restrict the diet of their dogs away from what those people prefer to eat.^[1] An analysis of a specimen from the Eliseevichi-1 site on the Russian plain also revealed that the Paleolithic dog ate reindeer.^[11]

In 2020, a study of dental microwear on tooth enamel for canine specimens from Predmosti dated 28,500 YBP suggest a higher bone consumption for the proto-dogs compared with wolf specimens. This indicates two morphologically and behaviourally different canine types. The study proposes that the proto-dogs consumed more bone along with other less desirable food scraps within human camps, therefore this may be evidence of early dog domestication.^[12]

See further Paleoecology of the time

Among archeologists, the proposed timing of the development of a relationship between humans and wolves is debated. There exists two schools of thought.^[18] The early domestication theory argues that the relationship commenced once humans moved into the colder parts of Eurasia around 35,000 YBP, which is when the proposed Paleolithic dogs first began to appear.^[6][27][59] Wolves that were adjusting to live with humans may have developed shorter, wider skulls and more steeply-rising foreheads that would make wolf facial expressions easier to interpret.^[18] The late domestication theory argues that Paleolithic dogs are an unusual phenotype of wolf and that dogs appeared only when they could be phenotypically distinguishable from the wolf, which is usually based on a reduction in size.^{[60][61][62][34][63]} This argument maintains that domesticated dogs are more clearly identified when they are associated with human occupation, and those interred side by side with human remains provide the most conclusive evidence,^[61] commencing with the 14,200 years old Bonn-Oberkassel dog.

The debate centres around Homo sapiens and if they had entered into cooperation with wolves soon after they moved into Eurasia, and if so when and where did these wolves change into domesticated dogs. In arguing that domestication leads to reduction in size, the late domestication theory ignores that modern horses and pigs are larger than their wild ancestors. It also ignores that if hunter-gathers entered into a hunting relationship with wolves then there would be no need of selection for a reduction in size. A reduction in size would have occurred much later when humans moved into agricultural villages. The late domestication theory does not consider the possibility that humans may have formed a relationship with non-domesticated wolves and that dogs in the early stages of domestication might be indistinguishable from wolves. According to indigenous North Americans, over the past 20,000 years the canids living with them were wolves that could not be distinguished as dogs.^[18]

The problem in attempting to identify when and where domestication occurred is the possibility that the process of domestication occurred in a number of places and at a number of times throughout prehistory.^[18] Early dog remains have been found in different parts of the world. This suggests that dog domestication may have taken place in different regions independently by hunter-gatherers, in some cases at the same time^[64] and in other cases at different times,^[65] with different wolf subspecies producing different dog lineages.^[66][65] Therefore, the number of dog domestication events is not known.^[67] A study of the maternal mitochondrial DNA (mDNA) shows that dogs fall within 4 mDNA clades,^[22] indicating that dogs are derived from 4 separate lineages and therefore there may not have been a single domestication event.^[18]

A domestication study looked at the reasons why the archeological record that is based on the dating of fossil remains often differed from the genetic record contained within the cells of living species. The study concluded that our inability to date domestication is because domestication is a continuum and there is no single point where we can say that a species was clearly domesticated using these two techniques. The study proposes that changes in morphology across time and how humans were interacting with the species in the past needs to be considered in addition to these two techniques.^[68]

..."wild" and "domesticated" exist as concepts along a continuum, and the boundary between them is often blurred — and, at least in the case of wolves, it was never clear to begin with.

— Raymond Pierotti^[69]

In 2013, a major Mitochondrial DNA study has found that divergence times from wolf to dog implies a European origin of the domestic dog dating 18,800-32,100 years ago, which supports the hypothesis that dog domestication preceded the emergence of agriculture and occurred in the context of European hunter-gatherer cultures.^[22]

In 2009, a study proposed that there was a low frequency of recognized dog skulls in Upper Paleolithic sites because existing specimens had not yet been recognized as dogs. The study looked at the 2 Eliseevichi-1 dog skulls in comparison to much earlier Late Pleistocene but morphologically similar fossil skulls that had been found across Europe, and proposed the much earlier specimens were Paleolithic dogs that were morphologically and genetically distinct from the Pleistocene wolves living in Europe at that time. The study looked at 117 skulls of recent and fossil large canids. Several skulls of fossil large canids from sites in Belgium, Ukraine and Russia were examined using multivariate analysis to look for evidence of the presence of Paleolithic dogs that were separate from Pleistocene wolves. Reference groups included the Eliseevichi-1 prehistoric dogs, recent dogs and wolves.

The osteometric analysis of the skulls indicated that the Paleolithic dogs fell outside the skull ranges of the Pleistocene wolf group and the modern wolf group, and were closer related to those of the Eliseevichi-1 prehistoric dog group. The fossil large canid from Goyet, Belgium dated at 36,000 YBP was clearly different from the recent wolves, resembling most closely the Eliseevichi-1 prehistoric dogs and suggesting that dog domestication had already started during the Aurignacian. The two Epigravettian Mezine, Ukraine and Mezhirich, Ukraine skulls were also identified as being Paleolithic dogs. Collagen analysis indicated that the Paleolithic dogs associated with human hunter-gatherer camp-sites (Eliseevichi-1, Mezine and Mezhirich) had been specifically eating reindeer, while other predator species in those locations and times had eaten a range of prey.^[6][21]

Further studies later looked at wolf-like fossils from Paleolithic hunter-gatherer sites across Europe and proposed to have identified Paleolithic dogs at Predmosti (Czech Republic 26,000-27,000 YBP), Kostenki-8 (Russia 23,000-27,700 YBP), Kostenki-1 (Russia 22,000-24,000 BP), Kostenki-17 (Russia Upper Paleolithic) and Verholenskaya (Russia late glacial).^[26] In the human burial zone at the Predmosti site, 3 Paleolithic skulls were found that resemble those of a Siberian husky but they were larger and heavier than the modern husky. For one skull, "a large bone fragment is present between the upper and lower incisors that extends several centimetres into the mouth cavity. The size, thickness and shape of the fragment suggest that it could be a fragment of a bone of a large mammal, probably from a mammoth. The position of the bone fragment in the mouth and the articulated state of the lower jaw with the skull indicate that this mammoth bone fragment was inserted artificially into the mouth of the dog post-mortem." The morphology of some wolf-like fossils was such that they could not be assigned to either the Pleistocene wolf nor Paleolithic dog groups.^[27]

It has been proposed that based on the genetic evidence of modern dogs being traced to the ancient wolves of Europe, the archaeological evidence of the Paleolithic dog remains being found at known European hunting camp-sites, their morphology, and collagen analysis that indicated that their diet had been artificially restricted compared to nearby wolves, that the Paleolithic dog was domesticated. It has also been hypothesized that the Paleolithic dog may have provided the stock from which early dogs arose, or alternatively that they are a type of wolf that is not known to science.^[6][21] In 2016, a study discounted the use of the Paleolithic dogs from the Predmosti site as pack animals.^[70]

There has been ongoing debate in the scientific press about what the fossil remains of the Paleolithic dog might be, with some commenters declaring them as either wolves or a unique form of wolf. These include a first article proposing the Paleolithic dog,^[6] its refutation,^[60] a counter to the refutation,^[71] a second article,^[27] its refutation,^[61] a third article that includes a counter to the refutation,^[26] its refutation,^[62] a counter to the refutation,^[72] another refutation,^[34][63] support given based on bone collagen analysis,^[1] and the identification of an ancient paleolithic dog in Yakutia.^[29]

As the ancestor of the dog has not been identified by scientists, this debate continues.

Studies have suggested that it was possible for multiple primitive forms of the dog to have existed, including in Europe.^[73] European dog populations had undergone extensive turnover during the last 15,000 years that has erased the genomic signature of early European dogs,^[74][75] the genetic heritage of the modern breeds has become blurred due to admixture,^[56] and there was the possibility of past domestication events that had died out or had been largely replaced by more modern dog populations.^[74]

In 2016, a study proposed that dogs may have been domesticated separately in both Eastern and Western Eurasia from two genetically distinct and now extinct wolf populations. East Eurasian dogs then made their way with migrating people to Western Europe between 14,000 and 6,400 YBP where they partially replaced the dogs of Europe.^[76] Two domestication events in Western Eurasia and Eastern Eurasia have recently been found for the domestic pig.^[76][77]

As the taxonomic classification of the "proto-dog" Paleolithic dogs as being either dogs or wolves remains controversial, they were excluded from the study.^[76]

Ecological factors including habitat type, climate, prey specialization and predatory competition will greatly influence wolf genetic population structure and cranio-dental plasticity.^{[81][82][83][84][85][86][87][88][89]} Therefore, within the Pleistocene grey wolf population the variations between local environments would have encouraged a range of wolf ecotypes that were genetically, morphologically and ecologically distinct from one another.^[89]

There are a small number of Canis remains that have been found at Goyet Cave, Belgium (36,500 YBP)^[6] Razboinichya Cave, Russia (33,500 YBP)^[79] Kostenki 8, Russia (33,500-26,500 YBP)^[72] Predmosti, Czech Republic (31,000 YBP)^[27] and Eliseevichi-1, Russia (17,000 YBP).^[5] Based on cranial morphometric study of the characteristics thought to be associated with the domestication process, these have been proposed as early Paleolithic dogs.^[72] These characteristics of shortened rostrum, tooth crowding, and absence or rotation of premolars have been documented in both ancient and modern wolves.^{[60][87][89][80][90][91]} Rather than representing early dogs, these specimens may represent an extinct morphologically and genetically divergent wolf population.^[33][56][89]

However, regardless of it eventually proving to be either a proto-dog or an unknown species of wolf, the original proposal was that the "Paleolithic dog" was domesticated.^[6]

In 2021, a study found that the cranial measurements of a number of Paleolithic dog specimens exhibited a relatively shorter skull and a relatively wider palate and brain case when compared with Pleistocene and recent northern wolves, and that these features are the morphological signs of domestication.^[92]