The advancing ghost cult made ancestor worship inevitable.  The great weakness of ancestor veneration is that it promotes a backward-looking philosophy. 
Ancestor worship is based on the belief that the dead punished those who did not follow the rules that they had followed when they they were in the flesh.  Ancestor worshipers view the failure to have sons as the supreme calamity for all time and eternity.  The great strength in a veneration of ancestry is the value that such an attitude places upon the family.  Later this ritual developed into a pseudo seance at which ghosts were reputed to have appeared.  During a certain period, solar veneration became a species of ancestor worship. 
Jews tended to overhonor ancestors. 
Both the Greeks and the Romans favored monogamous marriage.  This custom prevailed in Europe for some five hundred years following the disruption of Greco-Roman civilization. 
Caused stagnation in China.  Confucius established respect for ancestral conduct.  Buddhism soon amalgamated with the lingering ritualistic practices of ancestor worship. 
Ancestor worship onetime constituted a decided advance in religious evolution, but it is both amazing and regrettable that this primitive concept persists in China, Japan, and India amidst so much that is relatively more advanced, such as Buddhism and Hinduism. 
See also: UB 87:3; UB 79:8.3; UB 94:5.7.