After cutting off the tails of mice for 20 generations, an experimenter found that the 21st generation was still born with tails This tends to disprove the theory of: natural selection survival of the fittest mutations inheritance of acquired characteristics

This experiment disproves the theory of **inheritance of acquired characteristics**.<br /><br />This theory, often associated with Jean-Baptiste Lamarck, proposed that traits acquired during an organism's lifetime could be passed on to its offspring. The mice tail experiment demonstrates that this is not the case. Despite the tails being removed for generations, the genetic information for tail growth remained and was passed on, resulting in tailed offspring.<br />