Mammoth Tooth Cross Section, USAMammoths existed during the Pliocene period, some 4. 8 million years ago. However, the earliest Woolly Mammoth (Mammuthus primigenius) was discovered in Eurasia, with its remains dating back only 150,000 years ago. Most Woolly Mammoths disappeared between 10 12,000 years ago with a few notable exceptions. Mammoth remains were discovered on St. Paul's Island off the coast of Alaska, dating around 6,000 years old, and on Wrangel Island north of Siberia,