information:filtering, information:classification
Taxonomy

Members of the genus Cervus (and hence early relatives or possible ancestors of the elk) first appear in the fossil record 25 million years ago, during the Oligocene in Eurasia, but do not appear in the North American fossil record until the early Miocene. The extinct Irish elk (Megaloceros) was not a member of the genus Cervus but rather the largest member of the wider deer family (Cervidae) known from the fossil record.

Until recently, red deer and elk were considered to be one species, Cervus elaphus, with over a dozen subspecies. But mitochondrial DNA studies conducted in 2004 on hundreds of samples from red deer and elk subspecies and other species of the Cervus deer family, strongly indicate that elk, or wapiti, should be a distinct species, namely Cervus canadensis. DNA evidence validates that elk are more closely related to Thorold's deer and even sika deer than they are to the red deer.

Elk and red deer produce fertile offspring in captivity, and the two species have freely inter-bred in New Zealand 's Fiordland National Park. The cross-bred animals have resulted in the disappearance of virtually all pure elk blood from the area. Key morphological differences that distinguish C. canadensis from C. elaphus are the former's wider rump patch and paler-hued antlers.