Dog Evolution Provides Update To Darwin's Theory

Did the hormonal rhythms of certain wolves contribute to their relatively fast evolution to domesticated dogs? That’s the basis of a UVic researcher’s new theory to help explain how species form. “Thyroid hormones may play a significant role in evolution,” says anthropologist Dr. Susan Crockford who specializes in archaeozoology (the study of how humans and animals interact over time). “While genes play a major role in evolution, they are also influenced by thyroid hormones which control many genes and general body functions, including behaviour.”
In her new book Rhythms of Life: Thyroid Hormone and the Origin of Species (2006), Crockford applies her theory to the evolution of the dog. Agreeing with many researchers that dogs evolved from a wolf ancestor relatively quickly and without direct human interference, Crockford contends that certain wolves evolved into dogs because of their specific rhythm of thyroid hormone production. These wolves had hormone patterns that made them more stress-tolerant and more likely to colonize early human settlements. After several generations of interbreeding, the offspring of these stress-tolerant wolves acquired the physical and behavioural characteristics of dogs instead of wolves.
Crockford applies this model to many other speciation events, including the evolution of brown bears to polar bears and the series of speciation events that led to the creation of modern humans.
Crockford’s theory will be showcased in a new PBS documentary called “Dogs that Changed the World,” scheduled to air as a two-part Nature special in spring 2007. For more information about Crockford’s book visit www.rhythmsoflife.ca

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