Camels and llamas are North American animals that left home
Camels evolved in North America, starting as a rabbit-sized creature with four toes on each foot. For tens of millions of years they never left. Then some crossed into Asia and others drifted into South America, and the ones that stayed behind died out.
The family appeared in the middle Eocene, around 50 to 40 million years ago, in what is now North America. Protylopus, one of the earliest, still had four toes; by about 35 million years ago Poebrotherium had dropped the outer two and reached the size of a goat. The ancestors of camels and of llamas went separate ways roughly 17 million years ago but stayed on the continent until Paracamelus walked over the land bridge to Eurasia around 6 million years ago. Much later, 3 to 2 million years ago, Hemiauchenia moved south during the Great American Interchange and gave rise to the llama line.
Fossil camelids were far more varied than today's. Titanotylopus stood 3.5 metres at the shoulder, against about 2 metres for the largest living species; Stenomylus was small and gazelle-like; Aepycamelus and Oxydactylus were tall, giraffe-like browsers of treetop leaves. The North American camelids vanished relatively recently, perhaps through early human hunting, climate change after the last ice age, or both, leaving the modern distribution almost the reverse of where the family began.
Seven species survive: the dromedary, the Bactrian camel and the wild Bactrian camel in one tribe, and llamas, alpacas, vicuñas and guanacos in the other. Despite the name even-toed ungulate, they have no hooves. They walk on two toes with nails and tough, leathery pads; the suborder name Tylopoda means padded foot in Greek, and camel pads spread wider at speed to ease pressure.
They also move oddly, swinging both legs on one side together. At a run they keep this pacing pattern, which stops front and back feet colliding and briefly lifts all four off the ground, giving riders a rocking motion. Several species ovulate only when triggered by mating. Wild Bactrian camels cope with salty water, and some herds even inhabit former nuclear testing grounds. The United Nations named 2024 the International Year of Camelids.
Source: Camelidae
