Early relatives of primates lived on the Canadian island of Ellesmere north of the Arctic Circle around 52 million years ago, as fossil finds show. The two species are the northernmost known representatives of these primatomorpha. Although the polar region offered a subtropical climate during the warm phase that prevailed at the time, the long arctic winters without sun still posed challenges for living beings. The knowledge gained from the fossil finds can also provide indications of how such ecosystems could react to future global warming.
The Canadian island of Ellesmere is located north of the Arctic Circle, only around 1000 kilometers from the North Pole. In the winter months, the sun hardly makes it over the horizon – in the darkest weeks of the year it does not rise at all. While an arctic-cold climate prevails there today, temperatures on Ellesmere Island were significantly higher in the early Eocene around 52 million years ago. The warm phase at that time created an almost subtropical climate on the Arctic island in which even crocodiles could live, as fossil finds show. For scientists, Ellesmere opens up insights into how an ecosystem has developed in the face of past global warming – and what changes could possibly be imminent in view of the current human-induced climate change.
Two new species identified
A team led by Kristen Miller from the University of Kansas at Lawrence has now analyzed two fossils found in the Margaret Formation fossil site on Ellesmere Island and dated to be around 52 million years old. “These are two new species of early relatives of primates, so-called primatomorpha,” explain Miller and her team. “The two specimens from Ellesmere are by far the northernmost known records of Palaeogene primatomorpha.”
Using jaw fragments preserved from both specimens, the research team determined that they are sister species, both belonging to the genus Ignacius – an extinct genus of mammals closely related to primates and widely distributed around 62 to 33 million years ago lived in parts of North America. The authors named the two newly discovered species Ignacius mckennai and Ignacius dawsonae in honor of paleontologists Malcolm McKenna and Mary Dawson, who explored Ellesmere decades ago and donated the fossils to the authors for further study.
Adaptation to harder food
“No primate relative has ever been found at such extreme latitudes,” Miller explains. Although temperatures around the Arctic Circle were significantly warmer 52 million years ago, life on Ellesmere Island required specific adaptations: “We think that the darkness of the Arctic winter was probably the greatest physical challenge for the animals in the environment at the time,” says Miller’s colleague Christopher Beard. “How do they survive six months of winter darkness even if it’s reasonably warm?”
The research team found an answer to this question by analyzing the jaws of Ignacius mckennai and Igancius dawsonae: “The teeth and even the jaw muscles of these animals have changed compared to their close relatives from mid-latitudes,” reports Beard. “In order to survive the long Arctic winters, when preferred foods such as fruit were not available, they had to switch to harder foods such as nuts and seeds.” Accordingly, the jaws and teeth of these arctic dwellers were significantly more robust than in related species.
Global warming then and now
Additionally, Miller and her team found that the two newly discovered species were slightly larger than their southern relatives — consistent with Bergmann’s rule, well-known in ecology, that states that species in colder climates tend to be larger than those in warmer ones. “But they’re still pretty small,” says Miller. “Some of their relatives from the middle latitudes of North America are really tiny. Of course, none of these species are related to squirrels, but I think this is the closest animal to help us imagine what they might have looked like. Most likely they lived in trees most of the time.”
The researchers say the adaptations of the two Arctic species during the early Eocene global warm phase could provide clues as to how some modern-day animals might evolve new traits in response to human-caused climate change. “Our study shows how a primate relative that is specialized for a certain environment can change due to climate change,” says Miller. If it gets too hot at the equator due to global warming, it is conceivable that some species will shift their range towards the poles – and there they will encounter conditions that require evolutionary adaptations.
Source: Kristen Miller (University of Kansas) et al., PLoS ONE, doi: 10.1371/journal.pone.0280114