Simple first cousins have a coefficient of relationship of 0.125, which is below the threshold considered in the paper. Received wisdom is that a coefficient b

Simple first cousins have a coefficient of relationship of 0.125, which is below the threshold considered in the paper. Received wisdom is that a coefficient below 0.25 doesn't cause serious deleterious effect. I have no idea if that's well supported, but I imagine it's relevant to why it wasn't studied.