Origins

Ancestry
The species' most likely ancestral candidate is Canis lepophagus, a small, narrow skulled North American canid of the Miocene era, which may have also given rise to C. latrans. After the extinction of the large bodied Borophaginae family, C. lepophagus developed into a larger, broader-skulled animal. Fossils of this larger form of C. lepophagus found in northern Texas may represent the ancestral stock from which C. lupus derives. The first true wolves began to appear at the end of the Blancan North American Stage and the onset of the early Irvingtonian. Among them was C. priscolatrans, a small species closely resembling modern-day C. rufus, which colonized Eurasia by crossing the Bering land bridge. The new Eurasian C. priscolatrans population gradually evolved into C. mosbachensis, which subsequently developed in the direction of C. lupus. The earliest identifiable C. lupus remains date back to the Middle Pleistocene, and occur in Beringia.

Subspeciation
MtDNA studies have shown that there are at least four extant C. lupus lineages; the most ancient is that of C. l. lupaster (native to North, West, and East Africa), which is thought to have originated as early as the Middle to Late Pleistocene. All other lineages occur together in the Indian Subcontinent, the oldest of which is the Himalayan wolf (native to the Himalayan region of eastern Kashmir, Himachal Pradesh, parts of Tibet and eastern Nepal), which is thought to have originated 800,000 years ago, when the Himalayan region was going through major geologic and climatic upheaval. C. l. pallipes, likely diverged from the Himalayan wolf 400,000 years ago. The youngest C. lupus lineage in India is represented by C. l. chanco (native to the northwestern Himalayan region of Kashmir), which originated 150,000 years ago. This last lineage, known as the Holarctic clade, expanded into Europe and North America, as shown by it sharing genetic markers with domestic dogs, European and North American wolves.

The now extinct Japanese wolves were descended from large Siberian wolves which colonised the Korean Peninsula and Japan, before it separated from mainland Asia, 20,000 years ago during the Pleistocene. During the Holocene, the Tsugaru Strait widened and isolated Honshu from Hokkaidō, thus causing climatic changes leading to the extinction of most large bodied ungulates inhabiting the archipelago. Japanese wolves likely underwent a process of island dwarfism 7,000–13,000 years ago in response to these climatological and ecological pressures. C. l. hattai (formerly native to Hokkaidō) was significantly larger than its southern cousin C. l. hodophilax, as it inhabited higher elevations and had access to larger prey, as well as a continuing genetic interaction with dispersing wolves from Siberia.

C. lupus colonized North America during the late Rancholabrean era through the Bering land bridge in at least three separate invasions, with each wave being represented by one or more different Eurasian gray wolf clades. Among the first to enter was a broad-skulled, hypercarnivorous ecomorph which never expanded its range below the Wisconsin ice sheet, likely due to competitive exclusion by C. dirus populations in the south, with both dying out during the Quaternary extinction event without leaving any modern descendants. The first gray wolves to permanently enter North America were the ancestors of C. l. baileyi, though these were followed and displaced by C. l. nubilus and pushed southwards. C. l. nubilus was in turn displaced from its northern range by C. l. occidentalis, likely during the Holocene, a process which may have continued into historic times.