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Floppy Ears and Curly Tails...
Why So Many Domesticated Animals Have Floppy Ears
Take a look at several domesticated mammal species and you might spot a number of similarities between them, including those cute floppy ears. The famous naturalist and evolutionary theorist Charles Darwin even observed in the first chapter of his On the Origin of Species that:
Not a single domestic animal can be named which has not in some country drooping ears […]
And it's not just the ears. Domesticated animals share a fairly consistent set of differences from their wild ancestors such as smaller brains, smaller teeth, shorter curly tails and lighter and blotchy coats: a phenomenon called the "domestication syndrome".
paper published this week in the journal Genetics poses a new explanation as to why so many domesticated animals have such a similar set of traits.Adam Wilkins, from South Africa's Stellenbosch Institute of Advanced Study, and colleagues propose that human selection has, in domesticated species, altered the development of the neural crest, an organ system present during embryonic development.
The dog has been befriended by humans for at least 11,000 years, longer than any other domesticated animal. They differ from their wild ancestor wolves in all the above listed features of domestication syndrome.
Dogs aren't the only examples, of course. Humans have also domesticated cattle, horses, sheep, goats … the list goes on.
In the late 1950s, Russian fox-fur-farmer-turned-geneticist [geneticist turned fox fur farmer to obsfuscate that he was a geneticist when it wasn't popular with the Soviets] Dmitry Belyaev set up a long-term experiment to find out whether he could selectively breed the wildness out of the silver fox, which was hard to breed because of its aggressive nature. In each generation of foxes, he bred from animals that showed the least aggression towards their captors.
It took him and his successor Lyudmilla Trut just 20 generations – only about 25 years – to create a line of silver foxes who from birth were tame enough to be kept as pets. For those who study evolution, this is an extraordinarily short time span.
But that wasn't the most surprising result. Although selected only for their temperament, the later generations of silver foxes also had shorter faces, smaller teeth, soft and droopy ears, curly tails and altered colour. {...}
In 1868, the same year that Darwin published an entire monograph on domestication, Swiss anatomist Wilhelm His Sr described what became known as the embryonic neural crest... { MORE SCIENCE } {...}
Wilkins and colleagues now propose a hypothesis that links the development of the neural crest with the body changes that accompany domestication.
The neural crest produces not only facial skeletal and connective tissues, teeth and external ears but also pigment cells, nerves and adrenal glands, which mediate the "fight or flight" response. {MORE SCIENCE} {...}
This new hypothesis proposes one intriguing answer to the domestication question originally identified by Darwin and illustrated by Belyaev and Trut: why do all the traits of domestication co-exist in multiple species?
It may be that neural crest contributions are so diverse that it's possible to cherry-pick points of congruence to support any hypothesis. Nevertheless, the researchers suggest several lines of molecular genetic and functional experiments that can further put their ideas to the test...
Full Article: HERE
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In "The Genius of Dogs" the writer visited the facility, revealing that Belyaev wasn't really a furrier except inasmuch as it facilitated (and masked) his research.