Sex & Death: Introduction to the Philosophy of Biology Chapter 4: The Organism Strikes Back

Overview The Organism Strikes Back 4.1 What is a gene? “Evolutionary Gene” fails Invisibility Argument 4.2 Genes are active germ line replicators First attempt to redefine “gene” 4.3 Genes are difference makers Second attempt to redefine “gene”

4.1 What Is a Gene? Argument against gene selectionism: Sober (1984b) distinguishes between selection for and selection of. In gene selectionism only interested in selection for

Debate on visibility of genes to selection: Area 1: Explores which DNA sequences count as genes Area 2: Explores the complexity of the relationship between the genes and the phenotypes that they help to build

Area 1:What is a gene? First Definition: a gene is a “reading sequence” Second Definition: Dawkins and Williams, ‘evolutionary gene concept’ Critics object to this second definition since it does not have a systematic phenotypic relationship.

What is Phenotypic power? Two Responses: 1: Molecular genes: genes are functional biochemical units 2: Genes are “difference makers”

4.2 Genes are active Germ Line Replicators Dawkins (1982, 83) and active replicator is: “any replicator whose nature has some influence over its probability of being copied” 3 Criteria needed for the invisibility argument: 1)A constant phenotypic effect 2)Excludes impostors like individual nucleotides 3)The phenotypic effect of genes makes them more likely to be replicated

4.2 Genes are active Germ Line Replicators Problem: There is not always a constant phenotypic effect and hence condition one is not met. But: There are a few cases where there is a constant phenotypic effect

4.3 Genes Are Difference Makers There are no genes for traits but for trait differences Despite this being the more commonly used way of defining genes, it is ambiguous

4.3 Genes Are Difference Makers Disadvantage of viewing genes as ‘difference makers’ is that it becomes unclear whether they have an independent reality as a gene If this functional definition is not tied to anything molecular, it cannot be used in favour of gene selectionism as it speaks against cumulative selection: this is an empirical problem

Summary: Gene Selectionists have tried to formulate their conception of evolution in a manner which minimizes its vulnerability to empirical refutation First Attempt: evolutionary concept of genes Second Attempt: Genes as sequences of DNA that code for specific proteins

Summary: Third Attempt: Genes as ‘difference makers’: I.e. Make a difference in the phenotypic effect. Hence, to prove the gene selectionist view the empirical and conceptual problems need to be overcome.