Answer:
Hunting by the early humans is the appropriate answer.
Step-by-step explanation:
A set of huge animals, which thrived on Earth at the time of the Pleistocene epoch is known as the Pleistocene megafauna. These species got extinct during the Quaternary event of extinction. There are four theories, which have been considered as the probable causes of the extinction of Pleistocene megafauna. These are change in climatic conditions, hunting by humans, impact from a comet or an asteroid, and spreading disease. However, the majority of the evidence indicates that humans were the prime cause for the extinction to take place.