 Each of these aras progress into the next phase seamlessly without any apocalyptic consequences.The increase or decrease in the happiness, life spans and length of people and general moral conduct of the society changes in a phased and graded manner as the time passes.No divine or supernatural beings are credited or responsible with these spontaneous temporal changes, either in a creative or overseeing role, rather human beings and creatures are born under the impulse of their own "karmas".