It is widely agreed that the evolutionary lineage of the grey wolf can be traced back 2 million years to the Early Pleistocene species Canis etruscus, and its successor the Middle PleistoceneCanis mosbachensis.[2][3] The grey wolf Canis lupus is a highly adaptable species that is able to exist in a range of environments and which possesses a wide distribution across the Holarctic. Studies of modern grey wolves have identified distinct sub-populations that live in close proximity to each other.[4][5] This variation in sub-populations is closely linked to differences in habitat – precipitation, temperature, vegetation, and prey specialization – which affect cranio-dental plasticity.[6][7][8][9]
The earliest specimens of the modern grey wolf date to around 400,000 years ago,[10] or possibly earlier to 1 million years ago.[11] Most modern wolves share most of their common ancestry within the last 25-23,000 years from earlier Siberian wolf populations.[12][13][14][15] While some sources have suggested that this is the result of a population bottleneck, others suggest that this is a normal consequence of gene flow homogenising wolf genomes across their range.[16]