Different phases of evolution during ice age

A team of palaeontologists and palaegeneticists studied ancient fossil and DNA evidence for the nature and timing of changes animals and plants in the Northern Hemisphere.

They have shown that cold-adapted animals started to evolve 2.6 million years ago when the permanent ice at the poles became more prevalent. There followed a time when the continental ice sheets expanded and contracted and around 700,000 years ago the cold periods doubled in length. This is when many of the current cold-adapted species, as well as extinct ones like mammoths, evolved.

The findings have been published in the journal Trends in Ecology and Evolution.

“The cold-adapted species are amongst the most vulnerable animals and plants to ongoing climate change. Therefore, an understanding of how species evolved in the past is essential to help us understand the risks faced by endangered species today,” explained John Stewart, Professor of Paleoecology at Bournemouth University, who led the study.

During their research, the team compared the evidence for evolution in plants and beetles with that for mammals and suggested that ideas that some organisms had evolved earlier in the polar regions need to be tested. This means that the way the modern Arctic ecologies assembled needs to be resolved as it is not clear when and how the animals and plants who live there came together.

The study found evidence for early occurrences of true lemmings and reindeer in the Arctic where they may have evolved as climates cooled in the early Pleistocene period, between one and two million years ago. The polar bear and arctic fox on the other hand may have joined them more recently within the last 700,000 years — colonising from the South. Some of the ice age cold species like the woolly rhino are different and may have evolved in the steppe grasslands to the south with the earliest occurrences in the Tibetan Plateau.

“This is the first concerted effort to compare the evolution of cold-adapted animals and plants since modern methods of palaeogenetics appeared,” Professor Stewart said. “We can now build on these findings to understand more about how more cold-adapted species evolved and how the Arctic ecologies arose in the past and use this to help conservation efforts in the future,” he concluded.