History of the Universe eBook. 398 pages, 300 illustrations only £5.99
The weather grew colder until an ice age started 3 mya. Glaciers spread from the North Pole and from the mountains to cover much of the northern land. With so much water frozen into ice on land, sea level fell and dried out a lot more land than we see today.
Mammals evolved which could live on the ice. Woolly mammoth and other cold-loving mammals spread over northern lands.
More importantly from our point of view, humans began to spread across the Earth.
Data from European Project for Ice Coring in Antarctica (EPICA)
There were several interglacials within this ice age, like the one we are living through now. Most of the ice melted about 11 thousand years ago, starting the current interglacial. The climate reached its warmest about 5000 years ago, when it was much warmer than today. Since then (except for the current warming, probably due to human produced greenhouse gases) the weather has been getting colder.
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