Two TT commenters, Zachriel and Salvador Cordova have an interesting exchange ongoing in the open thread. Salvador initiated the discussion with this comment. In one of his comments Zachriel mentioned the genetic load concept. He also cited the following papers:
Nachman & Crowell, Estimate of the mutation rate per nucleotide in humans, Genetics 2000
Whitlock & Bourguet, Factors affecting the genetic load in Drosophila: synergistic epistasis and correlations among fitness components, Evolution 2000
In a recent comment Salvador said the following:
At the very least, it means, selection can't even detect or correct 108 new dysfunctional mutations per generation. On what grounds then can we suppose selection could have incorporated these mutations into the population in the first place?
This brings up an interesting question. If deleterious mutations accumulate within genomes without fatally compromising the survival of individual organisms until a threshold is reached, then what does this say about the role natural selection could have played in fixing such biological properties in the first place? At first glance it seems counterintuitive to think that x was selected for when x's disablement does not appreciably impact the fitness of the affected organism. So how does theory, and more importantly data, relate to Salvador's point?