Would you try to reverse any of the prehistoric m extinctions if your enemy was responsible for them?

Suppose that you had a time machine and used it to travel back to prehistoric times. You then find out that your worst enemy, who also happened to travel through time, was single-handedly responsible for all the major extinctions that happened in the past. Applying the concept of the erfly effect, past actions affecting the future, are you going to try to reverse any of those extinctions, knowing that it would change your own time line?