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 • Evolutionary Essentials
By two million years ago, during the Quaternary Period, the Earth’s continents were roughly in their current positions and massive glaciers had formed at the poles. Earth had entered an intense ice age that continues today. (We are currently in the warmer of the two cycles that make up an ice age.)
Many mammals had evolved to be massive, since bigger, better-insulated bodies survived cold weather better. These mammals spread across the globe as new land bridges connected continents.
The migration of these animals affected the course mammal evolution, introducing a key concept:
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Biogeography, which is the study of the history of landmasses and the life they have hosted.
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Continue to Biogeography. >>
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