Abstract

In this paper, we consider whether a straightforward answer can be provided to the following question regarding function ascriptions in genome biology: when does the activity of a genomic segment become functional or, perhaps, fully functional? We respond by examining de novo explanatory models for the emergence of genes, i.e., functional genomic entities. Our case study is especially pertinent to discussions about genome functionality, because what is meant by function, then, is crucial in assessing what constitutes a de novo gene origination. We show that, according to these models, there is no single point at which a genome segment acquires functionality. On the contrary, there is a continuum going from non-functional, through proto-functional, to fully functional. This suggests a gradational functionality for genomic objects, instead of an all-or-nothing one, as implied by standard views in the debate on biological functions. It has recently been argued by Matthewson (Biology Philos 35:4, 2020) that proper functions come in degrees because natural selection comes in degrees. We extend that argument and show that the continuum of functionality or, at least, proto-functionality, can be applied to genomic segments even before they are under the influence of natural selection. Accordingly, we argue that a weak etiological account is most suitable for capturing the phenomenon of new biological functions arising at the genomic level.