I heard an interesting talk at the Salk institute today by Richard E. Lenski about time travel in evolution. What they did over the last 25 years or so is to track over generations a strand of E. coli bacteria. Going back in time means taking out a batch from the freezer while going forward in time means just letting the bacteria evolve under controlled conditions. What they find if they look at the “fitness” of the bacteria is that they can describe this by a power-law, meaning that even under constant environmental conditions (the lab) the bacteria become better and more energy-efficient every day… and never stop. They just had a paper in Science on that.