  An idea is not a replicator because it does not consist of coded
self-assembly instructions. It may retain structure as it passes from one
individual to another, but does not replicate it. The cultural replicator is
not an idea but an associatively-structured network of them that together form
an internal model of the world, or worldview. A worldview is a primitive,
uncoded replicator, like the autocatalytic sets of polymers widely believed to
be the earliest form of life. Primitive replicators generate self-similar
structure, but because the process happens in a piecemeal manner, through
bottom-up interactions rather than a top-down code, they replicate with low
fidelity, and acquired characteristics are inherited. Just as polymers catalyze
reactions that generate other polymers, the retrieval of an item from memory
can in turn trigger other items, thus cross-linking memories, ideas, and
concepts into an integrated conceptual structure. Worldviews evolve idea by
idea, largely through social exchange. An idea participates in the evolution of
culture by revealing certain aspects of the worldview that generated it,
thereby affecting the worldviews of those exposed to it. If an idea influences
seemingly unrelated fields this does not mean that separate cultural lineages
are contaminating one another, because it is worldviews, not ideas, that are
the basic unit of cultural evolution.
