From The New York Times:
Humans are born time travelers. We may not be able to send our bodies into the past or the future, at least not yet, but we can send our minds. We can relive events that happened long ago or envision ourselves in the future.
New studies suggest that the two directions of temporal travel are intimately entwined in the human brain. A number of psychologists argue that re-experiencing the past evolved in our ancestors as a way to plan for the future and that the rise of mental time travel was crucial to our species’ success. But some experts on animal behavior do not think we are unique in this respect. They point to several recent experiments suggesting that animals can visit the past and future as well.
The first clues about the twists and turns of mental time travel came from people with certain brain injuries that caused them to forget autobiographical details without forgetting the information they had picked up along the way. A man known in the scientific literature as K.C., for instance, could play chess with no memory of having ever played it. K.C. could remember sentences psychologists taught him without any memory of the lessons.
More here.