From New Scientist:
Senior citizens played an important role in the dramatic spread of human civilisation some 30,000 years ago, a study of the human fossil record has shown.
…Anthropologists have long suspected that older people may have played an important role in the development of early human societies by providing extra care for children, helping to accumulate useful information and strengthening kinship bonds.
The so-called “grandmother hypothesis”, based on studies of African hunter-gatherer groups, suggests that infertile women are vital for successful child-rearing despite being unable to produce children themselves.
Prehistoric grandfathers invented smoking, drinking, games of chance and telling outlandish tall tales, all vital components of modern civilization.