In a recent post on The ID Report entitled, “Dog breeding – proof that Darwin was right? Hardly, says prof” there is some interesting information presented about neoteny. David DeWitt writes:
Many of the traits for different dog breeds are examples of neoteny.
Neoteny refers to the maintaining of juvenile characteristics into adulthood. Mutations can prevent proper development and maturation. Even though particular traits might seem like they are novel, in such cases it is really a loss of information since the animal has stunted development in one trait.
This is why some breeds of dogs are so cute and look like puppies even though they are full grown (Jack Russel, Shitzu etc).
Pure breed dogs often do have shorter lives than “mutts”. Presumably, this is because of severe inbreeding. The result is that mutations for particular diseases/defects become concentrated.
So when people have selected for those traits that comprise the poodle breed, they have also inadvertently selected several serious genetic defects. Certain breeds are prone to the same diseases and early causes of death.
Regarding the lack of aggression in dogs…this is also considered an example of a neotenous trait (juvenile traits that persist into adulthood).
When wolves are very very young, they are not so aggressive. Many of the behaviors of our dog breeds are also neotenous. There is plenty of information about this on the internet. The less a dog is physically like a wolf, the less aggressive the dog.
The most important thing to understand about dog breeding is that there is not new genetic information (from mutation) that is being supplied. Through breeding, humans are either shuffling genes that pre-exist in the population (like different poker hands from the same deck) or preserving mutations that amount to developmental defects.
While developmental defects can look like new traits (short stubby legs or a short snout for example or a Chihuahua that looks like an embryonic dog) they are not new at all since it is simply preservation of a previous stage.
Another example of a neotenous trait would be a mutation that leads to webbing between fingers in a human. During development, the cells between the fingers are supposed to go through a process of programmed cell death (apoptosis). If the cells do not die (because of a mutation), then the remaining tissue would be webbed fingers.
Since all human babies go through such a stage, it would not be a new trait even though it looks like it. It is preservation of a previous developmental stage because of a mutation in the normal developmental pathway. This highlights another aspect to the limits of Darwinian evolution.
Often, dogs are considered an exception because they are so “plastic”. In reality, it is just that we have been able to preserve a wider array of developmental defects. Dawkins pulled a real bait and switch trick when he criticized Behe’s Edge of Evolution using dog breeding. Dog breeds highlight the limits of evolutionary change, but Dawkins used the diversity of dogs (from developmental defects) to rebut this fact.