Thursday, 29 December 2011

Replicator rot

It does appear that some people have become confused about the role of high-fidelity copying in evolutionary processes - much as Henrich and Boyd (2002) claim.

Hull (1988) apparently based his theory of evolution on replicators, which he defined as follows:

replicator: an entity that passes on its structure largely intact in successive generations
The "largely intact" is problematical - cumulative adaptive evolution doesn't depend on high-fidelity transmission of structure - since low-fidelity transmission can be compensated for by error correction.

Let's call this mistake "replicator rot".

Aunger says this on the topic:

Any evolutionary process, including the cultural kind, needs only to exhibit features that correlate from one generation to the next. This quality is what biologists call heredity. Replication is a more precise claim about how evolution works — it suggests that a special kind of agent causes the recurrence of cultural features: a replicator. Some evolutionary approaches — competitors to memetics, such as sociobiology and evolutionary psychology — invoke only genetic heredity in their explanation of culture. I disagree. Socially transmitted information is central to the nature of culture. But when it is transmitted, is it replicated? That’s the crucial question.
He goes on to conclude that memes are replicators.

Dennett explains the basic evolutionary algorithm as being based on:

heredity or replication: the elements have the capability to create copies or replicas of themselves.
I think Dennett saves himself from replicator rot by including the terms "heredity" and "copies" - but it's a close call.

Blackmore and Dawkins mostly avoid the worst of the replicator rot as well - but they do so at the expense of giving the word "replicator" a counter-intuitive technical definition which avoids any mention of high-fidelity copying - with Dawkins (1982) saying:

I define a replicator as anything in the universe of which copies are made.
...and Blackmore (1999, p.5) saying:
a replicator is anything of which copies are made
Academic critics - such as Henrich and McElreath (2003) - typically finger Dawkins, Dennett and Blackmore - but their supporting evidence is usually inaccurate or vague.

Sue has said: "by definition, the information people copy is a replicator" and Dawkins has said: "Anything that is imitated is a form of replication". It seems clear that they don't intend any "high-fidelity copying" implications of the term "replicator" - and their explicit definitions of the term "replicator" confirm that this is indeed the case.

Dawkins did publicly succumb to replicator rot later on. In 2005's The God Delusion, page 191:

In its most general form, natural selection must choose between alternative replicators. A replicator is a piece of coded information that makes exact copies of itself, along with occasional inexact copies or 'mutations'.
This is simply wrong. Natural selection can choose between any items, whether they are frequently copied exactly or not.

In 2013, Dawkins offered:

Anything transmitted with high fidelity from brain to brain by imitation is a meme.
This is true - but it suggests that computer-based transmission doesn't count, and that high-fidelity copying is required. These both seem like highly dubious ideas.


No comments:

Post a Comment