The E. coli long-term evolution experiment is an ongoing study in experimental evolution led by Richard Lenski that has been tracking genetic changes in 12 initially identical populations of asexual Escherichia coli bacteria since 24 February 1988. The populations reached the milestone of 50,000 generations in February 2010 and 60,000 in in April 2014.

http://wikipedia.org/wiki/E._coli_long-term_evolution_experiment