Domestic dogs have an "incredible amount of diversity" which proves Charles Darwin's theory of the 'survival of the fittest' in a twisted way, a new American research suggests.
The study done by biologists Chris Klingenberg, of The University of Manchester and Abby Drake, of the College of the Holy Cross in the US has appeared in The American Naturalist.
Researchers compared domestic dogs' skull shapes with those of different species across the order Carnivora, to which dogs belong, along with cats, bears, weasels, civets, seals and walruses to come up with their conclusions.
It was seen that the skull shapes of domestic dogs were as much different as those of the whole order. It was also found that the extremes of diversity were farther apart in domestic dogs than in the rest of the order. What this means, for example, is that a Collie's skull shape is more different from that of a Pekingese than the skull shape of the cat is from that of a walrus.
Dr Drake said: "We usually think of evolution as a slow and gradual process, but the incredible amount of diversity in domestic dogs has originated through selective breeding in just the last few hundred years, and particularly after the modern purebred dog breeds were established in the last 150 years."
But the order Carnivora is almost 60 million years old. The amazing diversity in the shapes of the dogs' skulls categorically proves that selection plays a huge role in evolution and the level of diversity that separates species and even families can be generated within a single species, in this instance in dogs.
Majority of the diversity of domestic dog skulls is outside the range of variation in the Carnivora, and so represents skull shapes that are completely different.
Dr Klingenberg said: "Domestic dogs are boldly going where no self respecting carnivore ever has gone before.
"Domestic dogs don't live in the wild so they don't have to run after things and kill them - their food comes out of a tin and the toughest thing they'll ever have to chew is their owner's slippers. So they can get away with a lot of variation that would affect functions such as breathing and chewing and would therefore lead to their extinction.
"Natural selection has been relaxed and replaced with artificial selection for various shapes that breeders favour."
Drake pointed out: "Dogs are bred for their looks not for doing a job so there is more scope for outlandish variations, which are then able to survive and reproduce."
Dr Klingenberg added: "I think this example of head shape is characteristic of many others and is showing it so clearly, showing what happens when you consistently and over time apply selection.
"This study illustrates the power of Darwinian selection with so much variation produced in such a short period of time. The evidence is very strong."