In man, this retention or registration reaches perfection; he guides, himself by past as well as by present impressions; he is influenced by experience; his conduct is determined by reason.
A most important advance is made when the capability is acquired by any animal of imparting a knowledge of the impressions stored up in its own nerve-centres to another of the same kind.

This marks the extension of individual into social life, and indeed is essential thereto.

In the higher insects it is accomplished by antennal contacts, in man by speech.

Humanity, in its earlier, its savage stages, was limited to this: the knowledge of one person could be transmitted to another by conversation.

The acts and thoughts of one generation could be imparted to another, and influence its acts and thoughts.
But tradition has its limit.