The St Bernard dog – named after the 11th century priest Bernard of Menthon – is living proof that evolution does occur, say scientists.
Biologists at The University of Manchester say that changes to the shape of the breed’s head over the years can only be explained through human-directed evolution through selective breeding, an artificial version of natural selection.
The team, led by Dr Chris Klingenberg in the Faculty of Life Sciences, examined the skulls of 47 St Bernards spanning 120 years, from modern examples to those of dogs dating back to the time when the breed standard was first defined.
"We discovered that features stipulated in the breed standard of the St Bernard became more exaggerated over time as breeders selected dogs that had the desired physical attributes," said Dr Klingenberg.
"In effect they have applied selection to move the evolutionary process a considerable way forward, providing a unique opportunity to observe sustained evolutionary change under known selective pressures."
The findings, published in the Proceedings of the Royal Society B: Biological Sciences, are based on studies of St Bernard skulls donated by Swiss breeders to the Natural History Museum in Berne.
Compared to their ancestors, modern St Bernards have broader skulls, while the angle between the nose and the forehead is steeper in modern dogs and they have also developed a more pronounced ridge above the eyes.
"These changes are exactly in those features described as desirable in the breed standards. They are clearly not due to other factors such as general growth and they provide the animal with no physical advantage, so we can be confident that they have evolved purely through the selective considerations of breeders.
"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.
"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 research was funded by the Leverhulme Trust.
- Abby Grace Drake, Christian Peter Klingenberg. The pace of morphological change: historical transformation of skull shape in St Bernard dogs. Proceedings of The Royal Society B Biological Sciences, 2008; 275 (1630): 71 DOI: 10.1098/rspb.2007.1169
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