The large ice sheet that covered most of Canada and the northern fringes of the USA from around 100,000 to 10,000 years ago (during the Wisconsin glaciation) kept the Red foxes in Alaska (the population of which was added to by a second wave of colonisation from Eurasia) separate from those in the southern USA.
So, the result was two isolated populations (or clades): one in Alaska (Holarctic clade) and one in the south (Nearctic clade).
There is then something of a hiatus in the vulpine fossil record until the early Pliocene (about 4 mya), with foxes from China and Turkey among the earliest Eurasian specimens.
The origins of our modern-day Red fox (, which lived in southern Europe at the end of the Pliocene, around 2.6 mya – this species was first discovered in deposits from Italy in the late 1800s, but remains were subsequently found in France, Spain and Greece.
Nonetheless, taxonomists (those who study how species are related to each other) currently think that the carnivorans evolved from animals called miacids, which were small tree-living mammals that looked similar to modern-day civets.
Around six mya, the first wolf-like dog arrived in western Europe.According to Wang and Tedford, the first true foxes appeared in North America late in the Miocene (around 9 mya) and were represented by a small Californian species known as , which was found in the Central African country of Chad and dates to the late Miocene (some 7 mya).Recent work by Louis de Bonis and colleagues at the Université de Poitiers in France has suggested that the foxes and other canids first spread throughout Africa, before invading Europe via a trans-Mediterranean route towards the end of the Miocene.When the ice melted the Holarctic clade spread south and east, while the Nearctic clade spread north, the two meeting in central Canada.Aubry’s data reveal more than just the distribution of foxes in pre-history, it also elucidates the relatedness of the animals currently inhabiting North America (see: Taxonomy).Recent genetic work by Keith Aubry and his colleagues at the Pacific Northwest Research Station in Washington, however, has revealed new information on the spread of the Red fox in North America.