Simplify the following text for a Grade 5 native English-speaking person.
Original: The dates derived show that all forms of megafauna became extinct in the same rapid timeframe â '' approximately 47,000 years ago â '' the period of time in which humans first arrived in Australia .
Simplified: The dates show that the last of the megafauna became extinct around the same time , about 47,000 years ago . This was the time in which humans first arrived in Australia .