In Stalin's USSR the science of genetics was deemed "reactionary and decadent".
Scientists were sent to the gulags or simply disappeared. Dmitri Konstantinovich Belyaev lost his job at the at the Central Research Laboratory of Fur Breeding in Moscow because of his commitment to classical genetics. His brother, also a geneticist, was arrested by the secret police and shot without trial.
In 1959, after Nikta Khrushchev rose to power, Belyaev's fortunes changed and he was able to pursue his interest in the domestication of wild animals. Belyaev noted that most domestic animals had undergone the same basic changes.
- Their bodies changed in size and proportions.
- The normal pattern of coat color that had evolved as camouflage in the wild altered as well.
- Hair turned wavy or curly and some animals' hair also became longer.
- Many breeds of dogs and pigs carry their tails curled up in a circle or semicircle.
- Some dogs, cats and sheep have short tails resulting from a decrease in the number of tail vertebrae.
- Ears became floppy.
Another major evolutionary consequence of domestication is loss of the seasonal rhythm of reproduction. Most wild animals are genetically programmed to mate once a year while domestic animals can mate and bear young more than once a year and in any season.
Belyaev had an important insight. He suspected that all of these changes were predicated on just one trait - an animal's willingness to approach humans.
In 1959 he began an experiment that is still ongoing more than 50 years later. He chose as his subject the Silver Fox Vulpes vulpes. Officially his objective was to breed for better fur quality but in reality he was selecting only for tameness.
He began with 30 male foxes and 100 vixens. At seven or eight months, when cubs reached sexual maturity, they were scored for tameness and assigned to one of three classes. Only the 20% who made the elite class - the most friendly - were allowed to breed.
The result of this breeding program conducted over more than 40 generations of silver foxes was a group of friendly, domesticated foxes. But as well as their tameness they also had floppy ears, short or curly tails, extended reproductive seasons, changes in fur coloration, and changes in the shape of their skulls, jaws, and teeth. They also lost their “musky fox smell.”
The key thing about this experiment is that selecting for a single behavioral characteristic- or selecting against fear and aggression – resulted in changes not only in behavior, but also in a whole range of physical and physiological features.
Belyaev's work demonstrates the amazing power of selection and the unexpected ways in which genetic effects are interconnected.
|Part 1 - Protein Functional Redundancy - - - - - -||Part 2 - DNA Functional Redundancy|
|Part 3 - ERVs||Part 4 - Smelly Genes|
|Part 5 - Vitamin C||Part 6 - Human Chromosome 2|
|Part 7 - Human Egg Yolk Gene||Part 8 - Jumping Genes|
|Part 9 - Less Chewing More Thinking||Part 10 - Non-Coding DNA|
|Part 11 - Tiktaalik||Part 12 - Lenski's E.coli Experiment|
|Part 13 - Morris Minor Bonnets||Part 14 - Joey Goes to Oz|
|Part 15 - Robinson Crusoe||Part 16 - Aquatic Mammals|