Proportionality of single nucleotide causation

Abstract

Assessing the proportionality of causal relationships help us pick out the most relevant causes of an effect. In this paper, I nuance and apply the concept of proportionality from the philosophy of causation debate to the mapping of associations between variations in single nucleotides in the DNA and complex phenotypic traits, such as cancer, bipolar disorder, and happiness. I discuss under what circumstances single nucleotides, as far as these can be understood as causes, may satisfy the criterion of proportionality in an interventionist understanding of causality. I suggest that the overall relatively low stability and explanatory power of such variants may indicate that, in the causation of complex phenotypic traits, there are alternative causal levels that are more proportional than the level of nucleotides. I suggest network modules as candidates for more proportional organism-internal causes of complex phenotypes. Additionally, I address the broadness of many phenotypic traits investigated in GWAS, as well as the selection between several different proportional causes of an effect.

Keywords: Causation; GWAS; Genetic explanation; Network modules; Proportionality; SNPs; Single nucleotide.