Tuesday, 18 June 2013

Blending inheritance is an oxymoron

Blending inheritance is a traditional topic in the study of the history of evolutionary theory. The story goes that it was thought that the observed blending together of parental traits in offspring would rapidly destroy any variation for evolution to act on - through regression to the mean. This puzzle was resolved with the rediscovery of Mendel's work, showing that inheritance of DNA genes is particulate.

The topic relates to memetics, since - supposedly - cultural evolution exhibits blending inheritance. This means that the objections to Darwin's theory of evolution which were discredited by the discovery of particulate inheritance destroy the prospect of a theory of adaptive cultural evolution and - blah, blah, blah.

My story here is that "blending inheritance" is confusing terminology. In universal Darwinism, blending is a form of selection - not a form of inheritance. What people call "blending inheritance" is better thought of as being selection or recombination operations followed by inheritance. However, to call this "blending inheritance" seems like an oxymoron to me. The term mixes together different sorts of operation (selection and inheritance) - concepts which are best kept separate.

Blending during selection is ubiquitous in organic evolution. Blending during imitation in cultural evolution is paralleled by blending during mimicry - which is widespread in nature. Cuckoo eggs mimic the eggs of their hosts. Tasty moths mimic poisonous ones. Insects mimic sticks and leaves for camouflage purposes. Tigers mimic dry reeds. Very often multiple models are copied from. A tiger does not just mimic one dry reed per-generation - probably influences from thousands of reeds are involved. Blending is a widespread evolutionary phenomenon - not something confined to cultural evolution.

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