1. cats
2. they were hunted by humans
3. Smilodons were not fast hunters.
4. They were very aggressive animals.
5. an extinct mammal known as the Smilodon
6. to emphasize how scary the Smilodon would be, and to entertain the reader with the word “smile” when talking about a Smilodon
7. and
8. Early humans hunted the Smilodon's prey, reducing their food supply.
9. Climate change may have caused changes in vegetation, which in turn affected the food supply of the Smilodon and their prey.
10. Climate change and competition over food from other hunters indirectly impacted the Smilodon's food supply, leading to their extinction.