Abstract
Declining populations are expected to experience negative genetic consequences of inbreeding, which over time can drive them to extinction. Yet, many species have survived in small populations for thousands of generations without apparent fitness effects, possibly due to genetic purging of partially deleterious recessive alleles in inbred populations. We estimate the abundance of deleterious alleles in a range of mammals and find that conversely to current conservation thinking species with historically small population size and low genetic diversity generally have lower genetic load compared to species with large population sizes. Rapid population declines will thus disproportionally affect species with high diversity, as they carry many deleterious alleles that can reach fixation before being removed by genetic purging.
