This video lecture is the first in HHMI's 2012 Holiday Lecture series on Changing Planet: Past, Present, Future. In his talk entitled, The Deep History of a Living Planet, Dr. Andrew Knoll describes life forms that have existed on our planet since its origin. The history of life in the fossil record represents the most recent 15 percent of the entire history of life on Earth. The deeper history is microbial. Life on Mars is addressed.