Addomesticamento del Micio: indizi dal Genoma.

Genome reveals clues to cat domestication 

 Cats and humans have shared the same households for at least 9,000 years, but we still know very little about how our feline friends became domesticated. 
An analysis of the cat genome led by researchers at Washington University School of Medicine in St. Louis reveals some surprising clues. 

Researchers at Washington University School of Medicine in St. Louis led an international  team that sequenced and analyzed the cat genome to better understand the animal's  domestication. Pictured is a blue Abyssinian [Credit: WikiCommons] 

Cats have a relatively recent history of domestication compared with dogs; canines arose from wolves over 30,000 years ago. 
"Cats, unlike dogs, are really only semidomesticated," said senior author Wes Warren, PhD, associate professor of genetics at The Genome Institute at Washington University. "They only recently split off from wild cats, and some even still breed with their wild relatives. So we were surprised to find DNA evidence of their domestication." 
One way scientists can understand the genetics of domestication is to look at what parts of the genome are altered in response to living together with humans, Warren added.

The researchers compared the genomes of domestic cats and wild cats, finding specific regions of the domestic cat genome that differed significantly. 
The scientists found changes in the domestic cat's genes that other studies have shown are involved in behaviors such as memory, fear and reward-seeking. 
These types of behaviors -- particularly those when an animal seeks a reward -- generally are thought to be important in the domestication process. 

"Humans most likely welcomed cats because they controlled rodents that consumed their grain harvests," said Warren. "We hypothesized that humans would offer cats food as a reward to stick around." 
This meant that certain cats that would normally prefer to lead solitary lives in the wild had an additional incentive to stay with humans. 
Over time, humans preferred to keep cats that were more docile. 

Cat genome project 
The cat genome sequencing project, funded by the National Human Genome Research Institute, part of the National Institutes of Health (NIH), began in 2007.
 The project's initial goal was to study hereditary diseases in domestic cats, which are similar in some cases to those that afflict humans, including neurological disorders, and infectious and metabolic diseases. 
To obtain the high-quality reference genome needed for this research, the team sequenced a domestic female Abyssinian cat named Cinnamon. 
They chose this particular cat because they could trace its lineage back several generations. This cat's family also had a particular degenerative eye disorder the researchers wanted to study. 
To better understand characteristics of domestication, the researchers sequenced the genomes of select purebred domestic cats.

Hallmarks of their domestication include features such as hair color, texture and patterns, as well as facial structure and how docile a cat is. 
Cats are bred for many of these types of characteristics. 
In fact, most modern breeds are the result of humans breeding cats for their favorite hair patterns. 
The team also looked at a breed called Birman, which has characteristic white paws. The researchers traced the white pattern to just two small changes in a gene associated with hair color. 
They found that this genetic signature appears in all Birmans, likely showing that humans selectively bred these cats for their white paws and that the change to their genome happened in a remarkably short period of time. 
The group also compared the cat genome with those of other mammals -- including a tiger, cow, dog and human -- to understand more about the genetics of cat biology. 
"We looked at the underlying genetics to understand why certain abilities to survive in the wild evolved in cats and other carnivores," said Michael Montague, PhD, the study's first author and a postdoctoral research associate at The Genome Institute.
 The differences they found in the cat genome help explain characteristics such as why cats are almost exclusively carnivorous and how their vision and sense of smell differ from other animals like dogs.

Solitary carnivores 
To digest their fatty, meat-heavy meals, cats need genes to efficiently break down fats. The team found particular fat-metabolizing genes in carnivores such as cats and tigers that changed faster than can be explained by chance. 
This more rapid change generally means these genes provide some sort of digestive advantage to carnivores that only consume animal proteins. 
The researchers did not find such changes in the same genes of the cow and human, who eat more varied diets and would not need such enhancements. 
Cats also rely less on smell to hunt than dogs.

So it is not surprising that the researchers found fewer genes for smell in cats than dogs.

 But they did find more genes related to an alternate form of smell that detects chemicals called pheromones, which allow cats to monitor their social environment, including seeking out the opposite sex. 
This ability is not as important to dogs, which tend to travel in packs. 

But it is crucial in cats, which are more solitary and may have more difficulty finding mates. 
Cats also have better hearing than most other carnivores, including an ability to hear in the ultrasonic range to better track prey. 
Their vision is also exceptional in low light. 
"Cats tend to be more active at dawn and dusk," said Montague, "so they need to be able to detect movement in low light." 
Accordingly, the team identified specific genes that likely evolved to expand cats' hearing range and their vision in low light. 
Even though the genomes of domestic cats have changed little since their split from wild cats, the new work shows that it is still possible to see evidence of the species' more recent domestication. 
"Using advanced genome sequencing technology, we were able to shed light on the genetic signatures of cats' unique biology and survival skills," said Warren. "And we were able to significantly jump start our knowledge about the evolution of cat domestication." 

The research appears Nov. 10 in the Proceedings of the National Academy of Sciences Early Edition. 


Author: Gaia Remerowski 


| Source: Washington University in St. Louis [November 10, 2014]

Il micio, 5.300 anni fa

Cat domestication 

traced to Chinese farmers 

5,300 years ago

Five-thousand years before it was immortalized in a British nursery rhyme, the cat that caught the rat that ate the malt was doing just fine living alongside farmers in the ancient Chinese village of Quanhucun, a forthcoming study in the Proceedings of the National Academy of Sciences has confirmed.

The Near Eastern Wildcat, native to Western Asia and Africa, is believed to be the primary
ancestor of all domestic cats now living around the globe [Credit: WikipCommons]

"At least three different lines of scientific inquiry allow us to tell a story about cat domestication that is reminiscent of the old 'house that Jack built' nursery rhyme," said study co-author Fiona Marshall, PhD, a professor of archaeology in Arts & Sciences at Washington University in St. Louis.

"Our data suggest that cats were attracted to ancient farming villages by small animals, such as rodents that were living on the grain that the farmers grew, ate and stored."

Set for early online publication in PNAS during the week of Dec. 16, the study provides the first direct evidence for the processes of cat domestication.

"Results of this study show that the village of Quanhucun was a source of food for the cats 5,300 years ago, and the relationship between humans and cats was commensal, or advantageous for the cats," Marshall said. "Even if these cats were not yet domesticated, our evidence confirms that they lived in close proximity to farmers, and that the relationship had mutual benefits."

Cat remains rarely are found in ancient archaeological sites, and little is known about how they were domesticated. Cats were thought to have first been domesticated in ancient Egypt, where they were kept some 4,000 years ago, but more recent research suggests close relations with humans may have occurred much earlier, including the discovery of a wild cat buried with a human nearly 10,000 years ago in Cyprus.

While it often has been argued that cats were attracted to rodents and other food in early farming villages and domesticated themselves, there has been little evidence for this theory.

These are field specimens from the site of Quanhucun showing key body parts and the presence of an aged animal with worn dentition. (A) Left mandible with worn fourth premolar and first molar; (B) right humerus; © left pelvis; (D) left tibia [Credit: PNAS]

The evidence for this study is derived from research in China led by Yaowu Hu and colleagues at the Chinese Academy of Sciences. Hu and his team analyzed eight bones from at least two cats excavated from the site.

Using radiocarbon dating and isotopic analyses of carbon and nitrogen traces in the bones of cats, dogs, deer and other wildlife unearthed near Quanhucan, the research team demonstrated how a breed of once-wild cats carved a niche for themselves in a society that thrived on the widespread cultivation of the grain millet.

Carbon isotopes indicate that rodents, domestic dogs and pigs from the ancient village were eating millet, but deer were not. Carbon and nitrogen isotopes show that cats were preying on animals that lived on farmed millet, probably rodents. At the same time, an ancient rodent burrow into a storage pit and the rodent-proof design of grain storage pots indicate that farmers had problems with rodents in the grain stores.

Other clues gleaned from the Quanhucun food web suggest the relationship between cats and humans had begun to grow closer. One of the cats was aged, showing that it survived well in the village. Another ate fewer animals and more millet than expected, suggesting that it scavenged human food or was fed.

Recent DNA studies suggest that most of the estimated 600 million domestic cats now living around the globe are descendants most directly of the Near Eastern Wildcat, one of the five Felis sylvestris lybica wildcat subspecies still found around the Old World.

Marshall, an expert on animal domestication, said there currently is no DNA evidence to show whether the cats found at Quanhucun are descendants of the Near Eastern Wildcat, a subspecies not native to the area. If the Quanhucun cats turn out to be close descendents of the Near Eastern strain, it would suggest they were domesticated elsewhere and later introduced to the region.

"We do not yet know whether these cats came to China from the Near East, whether they interbred with Chinese wild-cat species, or even whether cats from China played a previously unsuspected role in domestication," Marshall said.

This question is now being pursued by researchers based in China and in France.

Source: Washington University in St. Louis [December 16, 2013]