The all-purpose forelegs of the dogs became more specialized for running long distances by becoming less flexible and giving more support.
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However, a few million years later, the global climate started cooling significantly and the Rocky Mountains in North America had hit a threshold of growth that led to much drier continental interior.
And the new study has shined a light on how animals that were previously considered prey can evolve into predators.
“It’s reinforcing the idea that predators may be as directly sensitive to climate and habitat as herbivores”, said Janis.
Early dogs were smaller and preferred to ambush prey, while later wolf-like dogs tracked and ran down theirs.
The researchers examined elbows and teeth of dog fossils from the American Museum of Natural History in New York. Instead their flexible forearms allowed them to seize prey in close quarters – whatever small animal happened to be making its way through the forest.
A study of North American dog fossils as old as 40 million years suggests that the evolutionary path of whole groups of predators can be a direct outcome of climate change. In a study published this week in Nature Communication, the authors reported on their efforts to measure the impact this transition had on dogs and other carnivores. She went on to add that “Although this seems logical, it hadn’t been demonstrated before”. Dog fossils across time reveal a shift in body size and morphology that follows the trajectory of a drying climate, transitioning from forests to grasslands.
‘The elbow is a really good proxy for what carnivores are doing with their forelimbs, which tells their entire locomotion repertoire, said study leader Professor Christine Janis, from Brown University in Providence, Rhode Island.
After all, it was not advantageous to operate as a pursuit-and-pounce predator until there was room to run.
“There’s no point in doing a dash and a pounce in a forest”, Janis quipped.
If predators evolved with climate change over the last 40 million years, the authors argue, then they likely will have to continue in response to the human-created climate change underway now. “They’ll smack into a tree”, Janis said.
Dogs were the same but over the years evolved elbows that pointed downwards.
The findings suggest evolution is not just an “arms race” between predator and prey, but is a reaction to many complicated environmental factors.
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“Now we’re looking into the future at anthropogenic changes”, Janis concluded.
