The abdication system is a method of recommending tribal leaders in ancient times, which was taken by Yao, Shun and Yu. Until the establishment of the Xia Dynasty in Chuanqi, the abdication system perished.

Brothers eventually become brothers, and the death of father and son are two ways to inherit the throne in Shang Dynasty. Shang dynasty *** 17 generation, 30 kings. Among them, there are four brothers and sisters 14, father and son 12 and four uncles. Before Pan Geng moved to Yin, the brothers were brothers and sisters, and the father died and the son succeeded him. After Pan Geng moved to Yin, the brothers became brother and sister, and the father died and the son succeeded. It can be seen that before Pan Geng moved to Yin, the throne was inherited by brothers and sisters, supplemented by the death of father and son, and vice versa.

In the second year of the establishment of the Zhou Dynasty, Zhou Wuwang died, and Zhou Wuwang had ten brothers, but he did not have a younger brother, and made the eldest son recite (Zhou Chengwang) as king, indicating that the Zhou people found a way to solve the dispute of succession to the throne and completed the transition from the death of their father to the inheritance of the eldest son.

All the above are from the second chapter of Zhang's History of China's Political System, Reforming the Political System of Slave Society Countries.