Arctic cold didn't break the camel's back

The results of a study suggest that the ancestors to modern camels were giant creatures, almost 30 per cent larger than today’s camels. As many as 30 fossil fragments of a leg bone found on Ellesmere Island in Canada provide the first evidence of camels living in the High Arctic region, writes Kalyan Ray.

With scientists identifying the first evidence of the existence of extinct giant camels in Canada’s High Arctic, it appears that not only did the ancestor of the modern camel not have any problems living in an Arctic forest, but also that its hump evolved to survive in that climate. Arctic camels were almost 30 per cent larger compared to their modern counterparts.

The discovery is based on 30 fossil fragments of a leg bone found on Ellesmere Island, Nunavut and represents the most northerly record for early camels, whose ancestors are known to have originated in North America some 45 million years ago. Subsequently, the animals dispersed to Eurasia via the Bering Isthumus, a land bridge linking Alaska and Russia. The results suggest that the evolutionary history of modern camels can be traced back to a lineage of giant camels that was well established in a forested Arctic.

“We suggest that the paracamelus lineage (ancestor of camels) began in northern North America, spread west via the Bering land bridge to Russia, Asia and Europe eventually reaching Africa. The original dispersal would have happened at least 6-7 million years ago. (The oldest camel in Eurasia was in Spain and was 6-7 million years old). This means the High Arctic camel would be a descendant of the original northern North American population,” Natalia Rybczynski, a fossil hunter at the Canadian Museum of Nature and one of the principal investigators in the project, told Deccan Herald. Camels and llamas originated as a group (family: camelidae) in north America about 45 million years ago. They diversified, giving rise to about 90 species.

Paracamelus is the ancestor to modern camels — known mostly from the fossil record of the old world (Asia, Europe). The High Arctic camel is the closest relative to paracamelus.

Wood or camel bones?

The fossils look so similar to wood that determining them as camel bones was a challenge. “The first time I picked up a piece, I thought that it might be wood. It was only back at the field camp that I was able to ascertain it was not only bone, but also from a fossil mammal larger than anything we had seen so far from the deposits,” explains Rybczynski, relating the moment that she and her team had discovered something unusual.

The fossils were collected over three summer field seasons (2006, 2008 and 2010) and are about 3.5 million years old, dating from the mid-Pliocene Epoch (5.3 million to 2.588 million years ago) from a steep slope at the Fyles Leaf Bed site, which is a sandy deposit near Strathcona Fiord on Ellesmere Island. Other fossil finds at the site suggest that High Arctic camels lived in a boreal-type forest environment, during a global warm phase on the planet when the earth was two to three degrees warmer than today and the Arctic was 14-22 degrees warmer.

“It is likely that Ellesmere camels survived winters with very low temperatures and they spent almost six months in a year in 24-hour darkness,” the team comprising Canadian and UK researchers reported in March 5 edition of Nature Communications. “This is an important discovery because it provides the first evidence of camels living in the High Arctic region,” explains Rybczynski. “It extends the previous range of camels in North America northward by about 1,200 km, and suggests that the lineage that gave rise to modern camels may been originally adapted to living in an Arctic forest environment.”

Analysing fossil fragments

Key physical characteristics suggested fossil fragments were part of a large tibia, the main lower-leg bone in mammals, and they belonged to the group of cloven-hoofed animals known as arteriodactyls, which includes cows, pigs and camels. Digital files of each of the 30 bone fragments were produced using a 3D laser scanner, allowing for the pieces to be assembled and aligned. The size of the reconstituted leg bone suggested it was from a very large mammal. At the time in North America, the largest arteriodactyls were camels.

Full confirmation that the bones belonged to a camel came from a new technique called ‘collagen fingerprinting’ done at the laboratory of Mike Buckley at the University of Manchester in the UK. Profiles produced by this technique can be used to distinguish between groups of mammals.

Minute amounts of collagen, the dominant protein found in bone, were extracted from the fossils. Using chemical markers for the peptides that make up the collagen, a collagen profile for the fossil bones was developed.

This profile was compared with those of 37 modern mammal species, as well as that of a fossil camel found in the Yukon, which is also in the Canadian Museum of Nature’s collections.

The collagen profile for the High Arctic camel most closely matched those of modern camels, specifically dromedaries (camels with one hump) as well as the Yukon giant camel, which is thought to be Paracamelus, the ancestor of modern camels. The collagen information, combined with the anatomical data, allowed Rybczynski and her colleagues to conclude that the Ellesmere bones belong to a camel, and is likely the same lineage as paracamelus.

“We now have a new fossil record to better understand camel evolution, since our research shows that the paracamelus lineage inhabited northern North America for millions of years, and the simplest explanation for this pattern would be that Paracamelus originated there,” explains Rybczynski. “So perhaps some specialisations seen in modern camels, such as their wide flat feet, large eyes and humps for fat may be adaptations derived from living in a polar environment.”