Externalities define memes in terms of their observable expressions (cultural artifacts, behaviors etc.)
What is common to both camps is that they both attribute memes their own "urge to reproduce themselves", which is independent (and sometimes even contradictory) to needs of the "host" organism.
examples: language, rituals, songs, taking selfies, internet memes, chain letters, fashions and styles, WC prose, earworms, what else ?
