Interesting. What does 'slippery' mean in this context?

(answered my own question: mutation rate from generation to generation in dogs is higher on average than in primates. Mechanism is not clear; one hypothesis is that mammals have DNA error correction "machinery" in their cells that is less effective in the canine genome. It's also unclear whether this has any impact on the evolution of dogs in terms of them being somehow more malleable to selective breeding than other species).