from the animals-that-clean-up-after-themselves dept.
In domesticated animals, regardless of species, certain traits eventually appear over and over again. White faces, white body spots, reduced facial skeleton, shorter snout, smaller jaws, smaller teeth, and, yes, Floppy Ears. One would almost think that humans selected animals for cuteness. In fact, people, even primitive prehistoric people, domesticated animals based on nothing more than selecting the least aggressive, or least fearful, and cross breeding those for generations. Those that bolt or bite either escaped, or got eaten, but weren't kept around for breeding.
So why do these traits appear so often in almost all domesticated animals, from horses to rabbits, and from dogs to hogs?
Scientists from Harvard, Vienna, Berlin, and South Africa have a new theory.
These traits are called Domestication Syndrome (DS), and it turns out that selecting for tameness — lack of fear or aggression — is actually a proxy for selecting for reduced functionality (hypofunction) of a specific type of stem cell called Neural Crest Cells (NCCs).
NCCs are the vertebrate-specific class of stem cells that first appear during early embryogenesis at the dorsal edge ("crest") of the neural tube and then migrate ventrally throughout the body in both the cranium and the trunk, giving rise to the cellular precursors of many cell and tissue types.
In a nutshell, we suggest that initial selection for tameness leads to reduction of neural-crest-derived tissues of behavioral relevance, via multiple preexisting genetic variants that affect neural crest cell numbers at the final sites, and that this neural crest hypofunction produces, as an unselected byproduct, the morphological changes in pigmentation, jaws, teeth, ears, etc. exhibited in the DS.
No genetic evidence indicates that all the changes seen in domesticated animals are the result of mutations in any one specific "domestication" gene. The data strongly support a multi-gene cause of DS, centered upon the under-development of neural crest cells.
So when selecting for docile genes the Floppy Ears and White Blaze come along for the ride.
Related Stories
An international team of researchers has shown that circulating avian influenza viruses contain all the genetic ingredients necessary to underpin the emergence of a virus similar to the deadly 1918 influenza virus.
Searching public databases, the researchers, led by Yoshihiro Kawaoka of the University of Wisconsin-Madison, identified eight genes from influenza viruses isolated from wild ducks that possessed remarkable genetic similarities to the genes that made up the 1918 pandemic flu virus. The 1918 or "Spanish flu" pandemic was one of recorded history's most devastating outbreaks of disease, resulting in an estimated 40 million deaths worldwide.
The new work was published on June 11, 2014 in the journal Cell Host & Microbe. It shows that "there are gene pools in nature that have the potential to cause a severe pandemic in the future," says Kawaoka, an international authority on influenza and the senior author of the new report.
To assess the risk posed by a virus that could acquire all eight of the 1918-like genes, the team used reverse genetics methods to generate a virus that differed from the 1918 virus by only 3 percent of the amino acids that make the virus proteins. The resulting virus was more pathogenic in mice and ferrets that an ordinary avian flu virus, but was not as pathogenic as the 1918 virus and it did not transmit in ferrets via respiratory droplets, the primary mode of flu transmission.
Since pandemic risk escalates when a virus become transmissible, Kawaoka's group then conducted additional experiments to determine how many changes would be required for the avian 1918-like virus to become transmissible in ferrets, a well accepted model for influenza transmission studies. The researchers identified seven mutations in three viral genes that enabled the pathogen to transmit as efficiently as the 1918 virus. The resulting virus, composed of genetic factors circulating in wild and domesticated birds, demonstrates that the genetic ingredients for a potentially deadly and pandemic pathogen exist in nature and could combine to form such a virus, according to Kawaoka.
A study into the genetic basis of cognitive traits has found that about half of the genes that influence how well a child can read also play a role in their mathematics ability.
Dissecting how genetic and environmental influences impact on learning is helpful for maximizing numeracy and literacy. Here we show, using twin and genome-wide analysis, that there is a substantial genetic component to children's ability in reading and mathematics, and estimate that around one half of the observed correlation in these traits is due to shared genetic effects (so-called Generalist Genes). Thus, our results highlight the potential role of the learning environment in contributing to differences in a child's cognitive abilities at age twelve.
Importantly, our analyses show that a substantial proportion of the observed correlation in reading and mathematics abilities is due to genetics. If a large proportion of the genetic factors that affect these traits are pleiotropic, then the factors that lead to differences in an individual's abilities (or disabilities) are relatively more likely to be environmental. Understanding the aetiology of these patterns increases our chances of developing effective learning environments that will help individuals attain the highest level of literacy and numeracy, increasingly important skills in the modern world.
(Score: 2) by cafebabe on Saturday July 19 2014, @12:01PM
So, a mechanism may have been found for David Brin's observations about neoteny [davidbrin.com]?
1702845791×2
(Score: 3, Insightful) by opinionated_science on Saturday July 19 2014, @02:24PM
hmm, i read that link, and it completely avoids the known biology.
I'll throw a simple idea out there. Domesticated animals are chosen by humans for their ability to be domestic - and the type of animal shows it.
Dogs can be much larger than cats, because humans have bred them for >14000 years (from wolves), and the aggressive traits have become subdued (this is why fighting dog breeds are banned - these traits are essential and dangerous in the wild, but not at all safe for domiciles).
Cats as an organism are more dangerous than dogs. Hence, in the wild cats, typically exist as lone animals and not as packs. Basically, humans have bred cats to be as small as possible and still be a cat-like. Just look at a tiger's mannerisms...
The domestication of animals was initially part of the human society choosing their functionality e.g. rats and disease, snakes , spiders etc, horses,cows, elephants etc. for traction.,dogs and birds for hunting etc...
Since we are talking about human selection, I would argue the most prominent selection is that Disney made animals neotenous. e.g. Mickey Mouse. I am fairly sure that Stephen.J.Gould the eminent paleontologist made a note of this fact in one of his books...
Hence, all of the cartoon animals look "young", so people want they pet to look like the movies/tv.
Not much of a stretch...
(Score: 5, Insightful) by evilviper on Saturday July 19 2014, @03:08PM
There's plenty of reason to believe that humans weren't involved in systematic breeding that created domestic dogs, at all.
http://www.pbs.org/wnet/nature/episodes/dogs-that-changed-the-world/what-caused-the-domestication-of-wolves/1276/ [pbs.org]
That's nonsense. Cat's weren't tigers (or other large cat) that was selectively bred to be smaller and safer. Instead, domestic cats are basically identical to their wild cousins like the desert cat. [wikipedia.org] Over millennia of human cohabitation and breeding, they've genetically diverged a bit, but are still very close to their wild roots, unlike dogs.
It didn't happen like that with dogs, either. They're 100% grey wolf. There was no mixing of various canine species to get sizes or other traits:
http://www.pbs.org/wgbh/nova/nature/dogs-decoded.html [pbs.org]
Hydrogen cyanide is a delicious and necessary part of the human diet.
(Score: 1) by anubi on Sunday July 20 2014, @07:32AM
I have had a street cat adopt me... and she proceeds to have kittens.
Some of these kittens have taken to me... they became adorable little pets, and I gave them to anyone who wanted a kitten. I see these kittens years later, loved, and some making more kittens.
And some of her kittens are more like an electrical short-circuit... all full of spitz. Scary little things. They won't have a thing to do with me, and I won't force them into anything they don't want because I do kinda want to keep my fingers.
The way I see it, the neighborhood coyote has to eat too. He usually ends up with them.
I could see as long as cat, dog, and man have hung around each other, there is going to be a lot of ones with desirable traits cared for and have a significantly greater chance of reaching maturity and breeding. Those wild little spitzers, even if they do survive, are usually trapped and given to farmers to release in the barn for mice control where the little spitzer does not have to tolerate being handled by a human. Or at least around here, that is usually the fate of an unloved cat. Its a short tough life...
By doing this same thing countless others before me have done, I am just another link in the refining process. Selectively breeding without even thinking about it.
Not all cats are loveable. You may try, but all you will end up doing is contaminating the gene pool genes for nasty dispositions.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2) by frojack on Saturday July 19 2014, @06:09PM
Actually, cats never were subject to the breeding efforts of mankind until relatively recently (Less than a 1000 years).
Most studies show that cats entered the human household not much earlier than around 5000 years ago, and were not common house pets until about 3500 years ago in ancient Egypt, and only accepted much later in Greek and Roman society. Prior to that time cats were feral, but did they exist in cities and villages. Cats were originally attracted to villages because of the abundance of mice. Humans tolerated them for that reason.
It took the cats about 2500 years to fully domesticate mankind, and they refused to allow the invention of glazed windows, solid doors, mouse traps. and tin cans until that process was complete, preferring a steady supply of mice until the reliability problem of humans had been solved.
No, you are mistaken. I've always had this sig.
(Score: 0) by Anonymous Coward on Saturday July 19 2014, @11:55PM
You forgot 1 significant stage:
In Europe in the Dark Ages, they were seen as "familiars" of witches and an effort was made to exterminate all cats.
What followed was an explosion in the rat population and the Black Death.
More than a third of the human population died off.
Way to go there, guys.
-- gewg_
(Score: 0) by Anonymous Coward on Saturday July 19 2014, @06:47PM
I recall seeing that page years ago. I would summarize it as "women evolved to be adorable." Which seems pretty obvious. Just yesterday I saw a comment posted in response to photos of an attractive female model where some guy was expressing deep concern about her well being. It was pretty clear that he did not know her, but instinctively imagines that she is someone worth caring about. Meanwhile in reality she may be a terrible person...
(Score: 4, Interesting) by HiThere on Saturday July 19 2014, @07:18PM
This matches the results of the Russian experiment in breeding tame foxes. The explicitly selected only for tameness, and ended up with floppy ears, etc.
It's been quite puzzling. If this theory proves out, it will explain the results. It could also give a way to domesticate animals that have so far resisted it. (The foxes, though, were relatively domesticated in only a few decades, so perhaps it's often just that nobody really tried.)
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by frojack on Saturday July 19 2014, @08:54PM
Yes, the authors quoted heavily from the Russian experiments.
Also there is one theory that we domesticated only those animals that were domesticate-able (genetically susceptible), and a counter theory that we domesticated only those animals that proved easy and quick, and useful to domesticate.
The Russian Fox work suggests that the latter may be the case, and that even Zebras and Wildebeests might be domesticated if we tried.
No, you are mistaken. I've always had this sig.
(Score: 1) by albert on Saturday July 19 2014, @11:53PM
All I want for Christmas is a hippopotamus.
Give me a cute little hippo that won't crunch my skull.