University of Manchester researchers, led by Chris Klingenberg, examined the skulls of 47 St. Bernards spanning 120 years, from the time the breed's standard was first defined. They found features stipulated in the breed standard -- broader skulls, a steeper angle between the nose and forehead and a pronounced ridge above the eyes -- became more exaggerated as breeders selected dogs for the desired physical attributes.

In effect, said Klingenberg, the breeders provided a unique opportunity to observe sustained evolutionary change under known selective pressures.

"Creationism is the belief that all living organisms were created according to Genesis in six days by 'intelligent design' and rejects the scientific theories of natural selection and evolution," he said. "But this research once again demonstrates how selection -- whether natural or, in this case, artificially influenced by man -- is the fundamental driving force behind the evolution of life on the planet."

The findings appear in the journal Proceedings of the Royal Society B: Biological Sciences.