Complex sentence: The history of Limousin cattle begins in the period known as the Pleistocene (2.6 million to 12,000 years ago), when many megafauna roamed the Earth before they became extinct from environmental pressures such as climate change and hunting by humans during the late Pleistocene.
Split into simpler sentences: The history of Limousin cattle begins in the period known as the Pleistocene (2.6 million to 12,000 years ago). The period is when many megafauna roamed the Earth before becoming extinct from environmental pressures such as climate change and hunting by humans during the late Pleistocene.