Legend has it that a long time ago, mankind was ignorant to the extent of not knowing how to count or tell the years apart. The ever-benevolent Jade Emperor wanted to help mankind out. From there, the idea of a twelve-year cycle and the naming of each year in the cycle after an animal was born.
But how should the Jade Emperor choose twelve animals from among so many animals in the living world, while remaining impartial? To resolve this equitably, the Jade Emperor decided to hold a race involving all animals on his birthday. The first twelve animals to cross the river and reach the Heavenly Palace will have a year named after them, in the order of how they finished the race. The race became known as The Great Race and the twelve-year cycle was named the Chinese Zodiac.