Simplify the following text for a Grade 10 native English-speaking person.
Original: It is hypothesised that with the arrival of humans ( around 48,000-60 ,000 years ago ) , hunting and the use of fire to manage their environment may have contributed to the extinction of the megafauna .
Simplified: It is possible when humans came to Australia ( around 48,000-60 ,000 years ago ) , and began hunting and using fire , they may have caused the extinction of the megafauna .