Friday, 30 May 2014

Repology 101: reps

An early contribution to repology took place in 1976, when Dawkins introduced the concept of a "replicator" to biologists. In 1982, he wrote:

I define a replicator as anything in the universe of which copies are made.

The "replicator" terminology has gone on to be popular, but controversial. The controversy centres around the issue of the ordinary English term "replicator" strongly implying high-fidelity copying, while Darwinian evolutionary theory doesn't require high-fidelity copying in order to work - according to standard information theory - e.g. see John Von Neumann (1952) "Probabilistic logic and the synthesis of reliable organisms from unreliable components".

Repology is based instead on the "rep". A rep is defined as follows:

Rep: anything that has been copied from something else

High-fidelity copying is emphatically not implied. Instead, copying fidelity is an attribute of the rep. High-fidelity copying is not a defining trait.

Note that the definition differs from the Dawkins definition of "replicator" is that the child is the "rep", while the parent is the "replicator". Whether an entity is an ancestor can change during the course of their lifetime, while an offspring is always an offspring. Once a rep, always a rep. DNA sequences in mules are "reps", but they do not fit the definition of "replicators" - since they are never copied from.

Reps differ from a generalized version of the concept of "gene" - since you can have inheritance and heredity without copying. If we take "gene" to refer to the basic unit of heredity, this need not refer to a copied entity. For example, I inherited my grandfather's clock. However, I didn't copy it. Reps are not the basic unit in a science of heredity.

Having side-stepped the controversies associated with the replicator concept, repology should be able to put the science of copying on a firm foundation.

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