Several theories propose that the benefits of sex arise from the elimination of deleterious mutations. Population subdivision can influence selection on deleterious mutations in two ways, one genetic and the other ecological. While the genetic consequences (increased homozygosity) are well known, the ecological consequences have received less attention even though they may be more important. I will discuss how ecological factors determine the "softness" of selection and thereby influence degree of mutation load. Finally, I will present some data from fly experiments assessing some common assumptions about soft selection for the first time.