The Hardy-Weinberg principle says that allele frequencies in a population are stable and constant from generation to generation as long as
-  The population is large enough and changes in allele frequencies due to chance or accident are insignificant
-  Mating occurs at random
-  Mutation does not occur or if it does occur it must reach a state of equilibrium
-  All the members of the population survive and have equal reproductive rates.
Hardy and Weinberg, through this law, have been able to explain why a population as a whole with all its variations and genotype frequencies continue to remain unchanged for many generations.