An early relative of extant Old World camels, "Paracamelus", existed in the upper Miocene to Middle Pleistocene. Around 3–5 million years ago, the North American Camelidae spread to South America as part of the Great American Interchange via the newly formed Isthmus of Panama, where they gave rise to guanacos and related animals, and to Asia via the Bering land bridge. Surprising finds of fossil "Paracamelus" on Ellesmere Island beginning in 2006 in the high Canadian Arctic suggest that the extant Old World camels may descend from a larger, boreal browser whose hump may have evolved as an adaptation in a cold climate. This creature is estimated to have stood around nine feet (2.7 metres) tall. The Bactrian camel diverged from the dromedary about 1 million years ago, according to the fossil record.