Scientists have learned a bit more about how Arctic animals evolved. They've found that evolution of present-day animals in the Arctic region may be intimately connected to ancestors that first adapted to the cold in the high altitude regions of the Tibetan Plateau.
For the last 2.5 million years, our planet has experienced both cold and warm millennia-long cycles. During the cold periods, though, continental-scale ice sheets blanketed large tracts of the northern hemisphere. When things warmed up, the glaciers receded; this advance and retreat of ice has a hug...
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