Question

Study the timeline.



Based on the timeline, about how many years ago could the oldest mammalian organism have lived?

5 million years
200 million years
1.5 billion years
4.5 billion years

Answer 1

Based on the timeline you provided, the oldest mammalian organism is generally estimated to have lived around 200 million years ago. This is when early mammal-like reptiles (therapsids) began to rise, leading to the eventual emergence of true mammals. Therefore, the answer is approximately **200 million years** ago.