Tuesday, 18 March 2014

Unwanted dogmas from the modern synthesis

The modern synthesis of the 1930s and 1940s famously fused the thinking from Darwin, Mendel and population geneticists - resulting in a popular consensus relating to how evolution worked.

Evolution and genetics have been married ever since. However, Universal Darwinism really represents a divorce of evolutionary thinking from many of the ideas it acquired from genetics around that time.

In universal Darwinism, the main ideas from genetics and population genetics that Darwinism acquired in the modern synthesis - in particular that mutations are undirected and that mutation biases are not significant - are now seen as domain-specific - and not features of evolutionary processes in general.

Signs that a split between evolutionary theory and these ideas from genetics was going to be necessary were present early on, but things really started to go sour in the 1970s, starting with Lewontin (1970). Lewontin wrote:

Darwin's scheme embodies three principles (Lewontin 1):

  1. Different individuals in a population have different morphologies, physiologies, and behaviors (phenotypic variation).
  2. Different phenotypes have different rates of survival and reproduction in different environments (differential fitness).
  3. There is a correlation between parents and offspring in the contribution of each to future generations (fitness is heritable).
These three principles embody the principle of evolution by natural selection. While they hold, a population will undergo evolutionary change. It is important to note a certain generality in the principles. No particular mechanism of inheritance is specified, but only a correlation in fitness between parent and offspring. The population would evolve whether the correlation between parent and offspring arose from Mendelian, cytoplasmic, or cultural inheritance.

He pointed out the substrate neutrality of evolutionary theory, and explicitly invokes cultural inheritance as an example.

Evolutionary theory isn't dependent on DNA genes. In fact it is inclined to fool around with memetics - and other forms of inheritance not mediated by DNA. In these other domains, the dogmas about mutations being undirected and unbiased are unwanted baggage.

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