The rabbit is widespread because we humans have spread it, following the initial domestication event in France, no later than 800 AD. This was originally for meat and fur, with pet breeds appearing only from the late 18th century. Rabbits are now found, for example, on Middleton Island, a chilly speck of land 130 km (80 miles) off the south coast of Alaska, and on the Kerguelen archipelago in the Indian Ocean, which is about as remote a place as it's possible to get.
These animals are "feral", in the sense that they live wild, but are descended from domesticated stock. But, obviously, they must have come from somewhere in the first place, and that place is Europe. (In contrast, the cottontail rabbits of North America proved behaviourally unsuited to domestication, although the ancient Mexicans gave it a try). More specifically, the rabbit is truly native only to Spain, Portugal, and southern France, with the Romans having introduced the pre-domesticated form across the rest of Europe, where most people would think of it as wild today.
In fact, wild rabbits are rare in their native range today, due partly to land development but more importantly, two waves of lethal disease - myxomatosis in the 1950s, and RHD in the '90s. As a result, you may be surprised to learn that the rabbit is, officially, an endangered species. It's just that we don't count all those feral forms in that classification.
What can we say about the earlier history of the rabbit? Rabbits have been regarded as a keystone species - one whose presence is central to maintaining their native ecosystem - so that uncovering their history can also tell us something about the world in which they lived. In their case, that's both by the way that they affect the local plantlife by feeding on it, and thus affecting other creatures that rely on the plants, but also by being a key food source for predators. A great many medium-sized predators feed on rabbits, and they are particularly important to Iberian lynx and Spanish imperial eagles, both of which are threatened species today.
Genetic evidence has confirmed that there are two living subspecies of European rabbit. The nominate form (O. c. cuniculus) is that to which the original scientific name was applied in 1758. That was, of course, by Linnaeus, and since he was Swedish, it's the subspecies that is found in Sweden. Originally native to southern France and neighbouring parts of Spain, this is the one that became domesticated and to which virtually all modern rabbits belong.
The other subspecies (O. c. algirus) is found only in wild populations in southern Spain, Portugal, and some parts of North Africa, although it has also been introduced to places like the Canary Islands. It was never domesticated, presumably because once the other one had been, there was no point in starting again from scratch. Based on their degree of genetic divergence, the two subspecies are thought to have last shared a common ancestor around two million years ago, which therefore puts a minimum age on the species as a whole.
Trying to unravel how rabbits changed and spread over that time period relies on skeletal and fossil remains, and that turns out not be as easy to do as one might hope. Trying to distinguish different forms relies on the size of the skeletons and, in particular, on the precise shape of the third premolar tooth in the lower jaw. However, both of these things can change in response to changes in the climate and associated foodstuffs or to local genetic effects with little wider meaning.
A recent study examined the remains of over 1,200 fossil rabbits from across their native range, comparing with the modern species. The remains date from across the Middle and Late Pleistocene - the last four Ice Ages and the three interglacials between them. When we look at modern rabbits, there is evidence that they partially follow Bergmann's Rule, which states that, for suitably close relatives, the colder the climate, the bigger the animal. I say "partially" because there are exceptions, but, in general, rabbits living at more northerly latitudes grow larger than those further south, perhaps because a larger body makes it easier for a mammal to retain body heat.
The study confirmed that this held true in prehistoric times, too. The oldest rabbits in the study, living 650,000 years ago were particularly large, and this is the height of the Günz/Cromer/Don glaciation, when the ice sheets reached unusually far south. 220,000 years ago, during the height of the last-but-one interglacial, they are noticeably smaller and there is another significant increase from 70,000 years ago as the Last Ice Age approaches and cold coniferous forests spread south.
At the start of the Middle Pleistocene, rabbits were restricted to Spain, where local conditions were relatively mild. The first evidence for them crossing the Pyrenees dates to around 560,000 years ago, and the fossil site in that case is only in the northern foothills, so it may have been another 80,000 years before they reached into the French lowlands and were, at least temporarily, prevented from heading further east by the Rhône. Surprisingly, they don't seem to have reached Portugal until even later, 425,000 years ago. This is about the same time that they reached Italy, although they subsequently went extinct there.
Rabbits then retreated and returned in various waves as the climate worsened, then improved again. The last such migration occurred as the Last Ice Age was thawing, seeing rabbits spread along the Mediterranean coast, and finally crossing the Rhône.
During the Ice Ages, rabbits, like many other animals, would have been isolated in "refugia", relatively small patches of suitable habitat surrounded by those less favourable. In this case, the study identified at least four during the Last Ice Age: two along the Mediterranean coast of Spain, one stretching from central Portugal to southern Spain, and the other in southern France.
The last one would have been temporarily destroyed when the ice reached its worst, as evidenced by the fact that we have rich fossil deposits from the time in southern France, and they don't include rabbits at all - it was more a time for mammoths and the animals that lived alongside them. The limitation here may well have been the expansion of the tundra, the permanently frozen subsoil preventing them from digging burrows.
If the divergence date between the two subspecies is correct, however, this can cover only the last third of the rabbit's existence. It's history before that, during the Early Pleistocene, remains a mystery, not least because the oldest confirmed fossils for the species, from Andalusia and Valencia, only date back 700,000 years. However, a lot may depend here on how we are defining the species. Presumably, over the course of two million years, it must have changed a fair bit, and we wouldn't necessarily recognise those earlier forms as belonging to the same species from their bones alone, even if, genetically speaking, they actually did.
Crucially, there is a candidate: Gibert's rabbit (Oryctolagus giberti). First identified in 2008 from remains in southeastern Spain, it is now known to have lived across both Spain and Portugal, and to have reached at least southeastern France from around 1.8 to 0.8 million years ago. This means that it died out just before the oldest fossils of the modern rabbit are found, so if it's a direct ancestor, then either it's not a distinct species or, perhaps more likely, the date for the split between the living subspecies is off by a fair margin - perhaps due to mixing of genes with ancient stock at some point.
Today, the European rabbit is the only member of its genus. But other species have existed in the past. The Valdarno rabbit (Oryctolagus valdarnensis) lived at around the same time as Gibert's species, between 2.1 and 1.2 million years ago. However, it lived in Italy, and so isn't a likely candidate for the ancestor of the modern form.
The only other known Ice Age species is Lacoste's rabbit (Oryctolagus lacosti), known from France around 2 million years ago, at the beginning of the Pleistocene. The oldest species that can be assigned to the genus, however, is the Layna rabbit (Oryctolagus laynensis) from the Late Pliocene of Spain 3.5 to 2.5 million years ago, apparently dying out when the Ice Ages started. It's thought that these two species evolved from an even older, as yet unknown, species that may have lived across much of Europe during the comparatively warm Early Pliocene.
This would push the origin of the rabbit genus back about as far back as the last common ancestor of the hares and jackrabbits. If this hypothetical species existed, it would have been the first true rabbit.
[Photo by N. P. Holmes, from Wikimedia Commons.]
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