I know of a dog with a relatively high CI and it is perfectly normal. How can this observation be consistent with inbreeding being deleterious?
Animals with high CI that appear to be healthy do arise from time to time. From the creation of inbred lines in laboratory animals, we know that it is possible to create such animals with a CI of 100%. However, the evidence from the creation of these lines shows very clearly that the chance of creating such an animal is extremely low; and that in order to create such an animal, many thousands of animals will be born with serious health and reproductive problems. In a classic case of the creation of an inbred line of mice, only one of 20 lines survived; the rest went to extinction due to inbreeding depression Bowman and Falconer [1960] Genetical Research 1, 262-74. Furthermore, detailed examination of completely inbred animals often reveals abnormalities that are not evident to the naked eye.
