The History of South American Camels

The camel family is one of the smaller mammal families in the present day, containing just seven species, four of which are domesticated. Thus, if you don't consider, say, dogs to be distinct from wolves at the species level, one could reasonably argue that there are only four. Although these are all considered to belong to the same subfamily (with all the other subfamilies being extinct), they still fall into two branches: the 'true' camels in the Old World, and their counterparts in the Americas.

It should come as no surprise that members of the family are noted for their ability to survive in arid environments with minimal water. They are, for example, more efficient at absorbing water from their stomach than ruminants such as cattle and deer, and genetically resistant to heat stress and ultraviolet radiation. Nonetheless, while the word "camel" doubtless conjures up an image of one or more of the three Old World species (that is, the dromedary and the wild and domesticated versions of the Bactrian camel), the family also includes those four American species.

Technically referred to as lamins, these are the domesticated llama and alpaca, and their respective wild ancestors, the guanaco (Lama guanicoe) and vicuña (Vicugna vicugna). Evidence suggests that these two wild species last shared a common ancestor between two and three million years ago, at, or shortly before, the start of the Ice Ages. This is relatively recent, and they can still crossbreed, so that all four species are often placed in the same genus, Lama. Indeed, modern domesticated alpacas share several genes inherited from interbreeding with llamas, albeit this mostly seems to have happened after the Spanish conquest of South America, long after the initial domestication event.

Camels, however, originated in neither Asia nor South America, but North America. While the ancestors of the true camels probably entered Asia relatively early on, towards the end of the Miocene, the ancestral members of the llama group only reached South America when the Panama land bridge first joined the two continents around 2.7 million years ago. Which, you will note, more or less matches the time of the split between the two living genera.

At the time, however, they were not alone. There were many types of 'camel' in North America at the time, and several of them seem to have headed south when the newly reachable continent opened up opportunities. Back home, a combination of the Ice Ages and the arrival of humans finished them off, leaving just those who had already moved elsewhere surviving, in Asia, Africa, and South America.

But that still left far more llama-like animals in South America than there are today. In fact, over thirty different fossil species have been named at one point or another, although it's inevitable that some of these will turn out to be misidentifications of something already named, so that the actual number won't be quite that high. And we are talking a timespan of over two and a half million years, so it isn't as if they were all alive at the same time.

But, with the help of a recently published review of their history, we can put together a picture of what happened to all of those missing llama-like species, and how the surviving ones got to where they are.

Perhaps the first question is why the two living species survived the end of the Ice Ages, when all the others didn't. In the case of the guanaco, this may be down to its adaptability. True, both species are capable of living in harsh environments, but guanacos have a wider diet and can tolerate a wide range of different harsh habitats. Today, they are found wild in the Andes as far north as Peru, but also widely across the lowlands to the east, reaching all the way through Patagonia to the southern coast of Tierra del Fuego, as close to Antarctica as you can get without swimming.

The vicuña, on the other hand, had a harder time of it. The oldest vicuña fossils date from around the middle of the Ice Ages, while guanaco fossils are slightly older, but we can tell that, for much of that time, they, too, lived in Patagonia. Indeed, the so-called "slender llama" (Lama gracilis), an extinct species, has recently been reclassified as just being a regular vicuña, and we know of fossils fitting that description not far from Cape Horn, just like guanacos. 

They died out there around 13,000 BC, shortly before the end of the Last Ice Age and today are found only in the high Andes, from Peru to northern Chile. This may be because they are more selective feeders, preferring specific grasses that are adapted to cold, dry environments and the lowlands may simply have become too warm for their favourite food. They retreated to refuges in the mountains, where a previous mild period meant they were already established and, being far less willing to travel long distances than guanacos are, they basically stayed there. 

There were relatively few other llama-like animals in Patagonia at the time, although the comparatively large Owen's llama (Lama oweni) may have been one of them. This, and the last of the South American horses in the region died out between 12,700 and 11,000 BC. Two things were happening at this time and they were both probably relevant. Firstly, the warming that had disadvantaged the vicuñas ended with a dramatic cold snap known as the Antarctic Cold Reversal that saw the landscape change to icy tundra. 

Secondly... well, human hunters got there, and that's never good.

As for the central Andes, the oldest known vicuña fossils are from this region, dated to around 80,000 years ago, so they were already well-established by the time they were driven out of Patagonia. Guanacos had been there longer, going back 780,000 years, although Palaeolama had been there even earlier. Even the guanaco, however, had been there long enough that it must have moved about over the course of hundreds of millennia as Ice Ages came and went. 

At the height of the last one, for example, the local climate changed enough that there were lakes in the Atacama Desert, which, paradoxically, might have forced the arid-adapted vicuña up onto higher ground to the north. Over time, they developed adaptations to improve their ability to live at high altitude, such as large hearts and blood that is more efficient at absorbing scarce oxygen, which, given the lack of competition, gave them even less reason to leave.

Humans reached this, relatively inhospitable, part of the world only around 7,000 BC and are known to have actively hunted both guanacos and vicuña from at least 4,000 BC. That this wasn't similarly disastrous may be down to the fact that llamas and alpacas were first domesticated from their wild ancestors at around the same time, giving farming communities ready access to an alternative.

Further east lies the Pampas, the grassy savannah habitat south of the Amazon in northern Argentina, Uruguay, and southern Brazil. This too, underwent changes in climate over the years, which would surely have affected the animals living there. While it's too far north for guanacos today, they did live there for some of this time, although the more dominant species would have been those belonging to the genus Palaeolama, which was larger than modern llamas, and probably more able to subsist on forest browse than merely on grass. Eulamaops, a lesser-known genus about the size of today's largest llamas, lived alongside it.

A shift towards warmer and more forested environments as the Ice Ages came to an end should have been good news for both of these extinct forms, but by then, humans had reached the area, and neither survived, with Palaeolama dying out perhaps as recently as 1,500 BC. Going back further however, this was also the region where Hemiauchenia, potentially the common ancestor of guanacos and vicuñas, had lived after it entered South America from the northern continent. 

Hemiauchenia is also known from North America, where a great many other llama relatives lived that never chose to move south. By doing so, however, while it has long passed from the world, its presumed descendants lived on, ultimately receiving what may be one of the best guarantees of survival in the modern world: becoming a useful domesticated animal.

[Photo by "Goliath" from Wikimedia Commons.]