Final answer:
The Middle Pleistocene started around 781,000 years ago and ended 126,000 years ago, witnessing significant climatic changes and the Pleistocene Extinction event.
Step-by-step explanation:
The Middle Pleistocene began about 781,000 years ago and ended 126,000 years ago. This geological epoch was marked by significant climatic changes, which included the most recent glaciation period that started a little over 100,000 years ago and reached its peak about 18,000 years ago. The ice age of this glaciation period ended approximately 12,000 years ago. During peak glaciation, ice sheets sometimes two miles thick covered land around the North Pole, extending over much of present-day Russia, Scandinavia, the British Isles, Greenland, Canada, and the northern reaches of the United States. Furthermore, the Pleistocene Extinction event happened towards the end of this epoch, characterized by the disappearance of large megafauna in North America and other regions due to habitat changes and over-hunting by humans.