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NOVA presents the story of dogs and how they
evolved into the most diverse mammals on the
planet.
The program:
• discusses the evolution and remarkable
diversity of dogs.
• notes that there are currently more than 400
different breeds of dogs worldwide.
• relates two competing theories about how dogs were domesticated:
Stone Age humans adopted and selectively bred wolves for
tameness; wolves essentially “chose” domestication when they began
to forage for food near prehistoric dumps. There, tameness was an
advantage.
• considers why dogs have tails that stick up, droopy ears, and other
traits that are not found in the wolf gene pool.
• recounts an experiment in which foxes bred for tameness produced
dog-like traits, leading to speculation that the new traits were due to
different levels of hormones created as a byproduct of tameness.
• explores how dominance hierarchies in wolf society have
contributed to making dogs well suited to be pets.
• suggests that dogs specialized in specific behaviors—hunting,
tracking, pointing, retrieving—and that over thousands of years
humans used food to reward the dogs best at these behaviors.
These better-fed dogs then had an improved chance at surviving
and passing on their genes.
• proposes a theory that the diversity found in dogs is due to subtle
changes in the regulatory DNA that instructs when a gene turns on
and off.
• suggests that dogs’ remarkable ability to adapt to different environments is due to an extended critical period of social development.
• reviews the problem of genetic diseases due to extensive inbreeding
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