We’ve shared our homes with dogs for roughly 14,000 years, but the evolutionary roots of 'man's best friend’ stretch a lot further back through time.
As a group, dogs - or canids - appeared roughly 40 million years ago in North America. While they look very different to today’s dogs, these early dogs share many of the same characteristic features, such as long muzzles, upright ears, long, slender legs, bushy tails, and specialised sets of teeth designed for cracking bones and slicing through flesh.
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There are many different types of animals that belong to the family Canidae, not just domestic dogs and their closest living relatives wolves. This diverse family also comprises coyotes, foxes, jackals, dholes, and dingos.
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These canids share many extinct relatives that were, compared to their living descendants, a lot larger and a whole lot more deadly.
If you thought modern species such as grey wolves and painted dogs were some of the deadliest canids that have ever lived, think again…
10 deadliest prehistoric dogs
Dire Wolf
At the same time that hunter gatherers were domesticating dogs, dire wolves were running around North America. These extinct canids lived during the Pleistocene Period and only faced extinction as recently as 10,000 years ago, alongside many other iconic ice age mammals such as mammoths, mastodons, and sabretooth tigers.
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In terms of size, dire wolves are roughly 40% larger than today’s grey wolves. To put that into perspective, the largest grey wolf ever recorded - a 103kg behemoth from the Yukon, Canada - probably wouldn’t have looked out of place in a pack of dire wolves. They had larger teeth and stronger jaws too - adaptations for hunting big game such as horses, bison, camels, and ground sloths.
Contrary to their depiction in George R.R. Martin’s epic fantasy series ‘A Song of Ice and Fire’, dire wolves weren’t exclusively found in snow-covered habitats. Based on where dire wolf fossils have been found, it’s understood they preferred living on plains, grasslands, arid savannahs, temperate steppes, and forested mountains.
A recent study on dire wolf DNA has revealed that these deadly canids aren’t the closest ancestors of today’s grey wolves; they’re actually evolutionarily distant cousins that broke away from the wolf family tree some 5.5 million years ago. And unlike grey wolves, dire wolves may have sported shorter coats of reddish-brown fur, rather than shaggy grey coats.
Epicyon
As canids go, none are larger than Epicyon. The type species, Epicyon haydeni, is estimated to have measured 2.5m from nose to tail, stood 1m tall, and weighed in at 125kg. This makes Epicyon more comparable in size to a brown bear than your average labrador.
Epicyon belongs to a family of dogs known as the borophagines, or bone-crushing dogs. These dogs are characterised by their comparatively short, deep-set skulls and giant carnassials - specialised cheek teeth designed to break bones. Epicyon and other borophagines used their carnassials and powerful jaws to crush and chew bones, just like today’s hyenas do.
This ability to eat bones originally led researchers to hypothesise that Epicyon was a scavenger, but more recent evidence has suggested it was an active predator and may have even hunted in packs. If Epicyon did hunt in packs, then it would have been capable of hunting prey larger than itself, such as the 3m-tall camel Aepycamelus and/or the hippo-sized rhino Teleoceras - two large herbivores that lived alongside Epicyon in North America during the Miocene Period.
Epicyon may have been the largest (and deadliest) canid to ever live, but it ultimately faced extinction five million years ago. It’s thought that big cats, which migrated into North America from Eurasia roughly 18 million years ago, may have outcompeted Epicyon and slowly but surely drove it to extinction.
Sardinian Dhole
This extinct canid was no giant; weighing in at approximately 10kg, it was roughly the size of a Cocker Spaniel. However, its short, powerful limbs, long neck, and slender skull made it a formidable predator and one that specialised in the art of ambushing its prey.
The Sardian Dhole - or Cynotherium sardous - lived on the Mediterranean islands of Sardinia and Corsica during the Middle to Late Pleistocene and only faced extinction shortly after humans settled the islands roughly 16,000 years ago.
This diminutive but deadly canid shared its habitat with dwarf mammoths (Mammuthus lamarmorai) that stood no taller than an average human, though these were almost certainly off the menu. Instead, the Sardinian Dhole is thought to have preyed on small, fast-moving mammals, such as the Tyrrhenian field rat and the Sardinian pika.
The Sardinian Dhole appeared roughly 800,000 years ago, during a time when low sea levels in the Mediterranean prompted a dispersal of animals from mainland Italy to the then-attached islands of Sardinia and Corsica. As sea levels rose, the Sardnian Dhole found itself trapped. It was at this point that it probably evolved its unique set of adaptations.
Hesperocyon
This 80cm-long canid looks more like a civet or a raccoon than a dog, but it’s widely regarded as the first dog and the ancestor that gave rise to giants like Epicyon and dwarfs like today’s chihuahuas.
Hesperocyon lived approximately 40 million years ago and ranged from southern Canada to Colorado. It appeared just a few million years after dogs (caniforms) and cats (feliforms) split and started to follow their own distinct evolutionary paths, which explains why it looks like a hybrid of these two iconic animals.
Like today’s cats, Hesperocyon had a long, low-slung body and a long, flexible tail, but its legs were comparatively short. Its teeth were very different to those of cats and were what ultimately prompted researchers to group it with canids. However, unlike later canids, Hesperocyon had five toes and an enlarged ‘dew claw’ that some interpret as an adaptation for climbing trees.
While Hesperocyon wasn’t quite as deadly as some of its descendants, it was still a predator and one that likely hunted by pouncing on its prey in the same way that foxes and coyotes do today. It lived in woodlands and savannah-like habitats and preyed on small animals ranging from rodents to insects. It may have also eaten some plants.
Enhydrocyon
The family Canidae can be split into three distinct subfamilies: Hesperocyoninae, Borophaginae, and Caninae. So far, this list has covered at least one species from each. Enhydrocyon, however, blurs the lines between these groups.
As a relatively small and basal canid, Enhydrocyon belongs to the Hesperocyoninae subfamily, along with Hesperocyon - the ‘first dog’. However, unlike Hesperocyon, its snout was relatively short and it had deep-set jaws, more like those of a borophagine. Its legs were also longer than those of other hesperocyonines, meaning it was probably better at running and pursuing prey.
Enhydrocyon is widely considered the first type of canid adapted to be a specialised predator, pioneering a lifestyle that borophagines and canines would adopt later. Some think it may have also been hypercarnivorous and subsisted on a diet that consisted of more than 70% meat.
Like many early dogs, Enhydrocyon lived in North America during the Oligocene and Early Miocene (31 to 20 million years ago). It weighed in at roughly 10kg, so it was by no means massive, but its stocky build made it a deadly predator and more than capable of hunting some of the other medium-sized mammals that shared its grassland habitat.
Falkland Islands Wolf
The warrah, or Falkland Islands Wolf, is the only land mammal native to the islands it was named after. It became extinct as recently as 1876, but its origin and arrival on the Falkland Islands may predate many historical records.
When Charles Darwin visited the Falkland Islands in 1833, he and other European settlers assumed that they had never been inhabited by humans. That made sightings of warrahs - long-legged, fox-sized canids - particularly mysterious; how did this lone mammal make it to these islands hundreds of miles from the coast of Argentina without the help of humans?
For a time, it was thought warrahs may have rafted to the Falkland Islands on piles of matted vegetation, or on ice floes during the ice age. However, a 2021 study found evidence to suggest that they may have been brought to the islands by prehistoric seafaring humans long before the islands were ‘discovered’ by Europeans in the 17th century.
This same study revealed that the warrah’s diet was, for a time, heavily dominated by seals - animals that it wouldn’t have naturally preyed upon but may have been fed scraps of by humans. After they were abandoned on the Falkland Islands and up until their eventual extinction in the late 19th century, warrahs likely preyed upon the geese and penguins that live along the islands’ coasts.
Cynarctus
Although it may be a borophagine and belong to the subfamily of dogs best known as the bone-crushing dogs, Cynarctus is widely thought to have been omnivorous. It lacked the bone-cracking adaptations of later borophagines, such as Epicyon, and was instead equipped with narrower teeth and longer, more slender jaws.
Cynarctus has been described as living ‘more like a mini-bear’ than like a dog, subsisting on a diet of meat, insects, and plants. This doesn’t make it any less deadly than the other dogs on this list though; at roughly the same size of a coyote it was still larger than many of the animals that shared its grassland habitat.
Cynarctus lived during the Miocene (16-10 million years ago) and is known from fossils found in the US states of Colorado, California, Nebraska, and Texas. The discovery of a new species (Cynarctus wangi) in 2015 in Maryland extended the known range of the group far into northeastern North America.
There are several other species of Cynarctus; one of which - Cynarctus fortidens - is thought to have fed primarily on fruits, based on its rounded teeth.
Beringian Wolf
There are lots of different types of wolves, many of which are considered subspecies of Canis lupus - the modern grey wolf. The Beringian Wolf is one of these subspecies, and perhaps the largest. It lived in what is now modern-day Alaska and northwestern Canada during the Pleistocene, only facing extinction approximately 8,400 years ago.
The Beringian Wolf was similar in size to large grey wolves alive today, though it was notably more robust, with stronger jaws and teeth, a broader palate, and larger carnassials relative to its skull size.
This unique skull meant that the Beringian Wolf had a very powerful bite, strong enough to grapple with and subdue large prey such as horses, steppe bison, caribou, and possibly even mammoths.
As the ice age came to a close and its prey largely disappeared - likely due to a combination of rapid climate change and overhunting by humans - the Beringian Wolf became extinct. While it may have gone, the genes of the Beringian Wolf live on. In 2016, a study found that some wolves living in remote parts of China and Mongolia share a common maternal ancestor with a 28,000-year-old Beringian Wolf specimen.
Molossian Hound
It may have lived during documented history, but this list wouldn’t be complete without a mention of the Molossian Hound - a large, mastiff-like dog bred by the ancient Greek tribe known as the Molossians.
This giant dog breed was popular in the 4th and 3rd century BC, during the height of the Molossian expansion. The dogs produced by this tribe have been described as livestock guardian dogs that were similar in size to today’s largest mastiff breeds, which are known to exceed weights of 100kg.
The origin of the Molossian Hound is shrouded in mystery, though there are several speculative theories as to how it came about. One such theory is that Alexander the Great discovered some giant dogs in Asia during his conquests in the 4th century BC. He is said to have sent some home to Ancient Greece where they were later bred with other dogs to produce the Molossian Hound.
Describing Molossian Hounds in his text The History of Animals, philosopher Aristotle wrote, “those employed in following sheep are larger and more fierce [than other dogs] in their attacks on wild beasts.” He also added that dogs born from a mix of a Molossian Hound and a Laconian - another breed of dog from Ancient Greece - are known for their courage and “endurance of hard labour.”
Paleolitihic Dog
Every domestic dog alive today, from enormous English Mastiffs to tiny Toy Poodles, can trace their roots back to a common ancestor that lived during the ice age and at a time when hunter gatherers were becoming increasingly pally with populations of wild wolves.
It’s unclear exactly when wolves were domesticated by humans; genetic evidence suggests that the unknown species of wolf that dogs descend from may have split from extant grey wolves as early as 40,000 years ago.
That said, the Bonn-Oberkassel dog serves as stark evidence that, by at least 14,200 years ago, the ancestors of today’s dogs had been tamed, domesticated, and welcomed into our homes.
The Bonn-Oberkassel dog was discovered in 1914 in a basalt quarry buried alongside two humans. Signs of missing teeth and gum disease suggest the dog survived some tough times as a puppy and was likely nurtured by humans. A more recent study of the Bonn-Oberkassel dog’s DNA has revealed that it is a direct ancestor of modern dogs.
While there are many older examples of paleolithic ‘dogs’, the Bonn-Oberkassel dog is widely regarded as the first undisputed domestic dog in the archaeological record. Still, the exact timing and location of dog domestication is heavily debated.
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Top image: Dire wolves © Charles Robert Knight, Public domain, via Wikimedia Commons
