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Παρασκευή 26 Δεκεμβρίου 2014

Why cats never became man’s best friend...

"Wild at heart", από τον χρήστη του Flickr, Guyon Moree
Dog lovers will find it baffling that cats are the world’s most popular pet. 
After all, they’re passive-aggressive, emotionally unavailable, 
and known for their chilly independence—traits that at most qualify 
felines for the role of “man’s best frenemy.”


It turns out, though, there’s an evolutionary reason for this 
tense relationship. That is, cats are in many ways still wild.


“Cats, unlike dogs, are really only semi-domesticated,” 
says Wes Warren, professor of genetics Washington University and 
co-author of the first complete mapping (paywall) 
of the house cat genome—specifically, that of an Abyssinian 
named Cinnamon. 

Comparing the DNA differences between house cats and wild cats, 
Warren and his colleagues found that where the genes of domesticated 
kitties and wild cats diverge has to do with fur patterns, grace, and docility. The latter are the genes that influence behaviors 
such as reward-seeking and response to fear.


The context for this split is telling. The divergence likely began some 9,000 years ago, after humans had made the shift to agriculture. 
Drawn to the teeming rodent populations that gathered during grain 
harvests, wild cats began interacting with humans. 
And because cats kept rodents in check, the researchers hypothesize, 
humans likely encouraged them to stay by offering them food 
scraps as a reward. 
These early farmers eventually kept cats that stuck around.


“Selection for docility, as a result of becoming accustomed to humans 
for food rewards,” write the researchers, “was most likely the major force 
that altered the first domesticated cat genomes.” 
In other words, the ones that stuck around were the cats with those 
genes that encouraged interaction with humans, thereby making those traits prevalent in what became the global domestic cat population.


As intriguing, though, is what didn’t change in human-friendly cats 
during those nine millennia. House cats still have the broadest hearing 
range among carnivores, which allows them to detect their 
prey’s movement. They also retain their night-vision abilities and the 
ability to digest high-protein, high-fat diets. This implies that, 
unlike those of dogs, their genes haven’t evolved to make cats 
dependent on humans for food.


This indicates only a modest influence of domestication on cat genes, 
compared with dogs, say the researchers. In fact, according to 
recent research on canine genomes, dogs became man’s best friend back 
when humans were still hunting and gathering—between 11,000 
and 16,000 years ago. Their typically more omnivorous diets evolved 
as human lifestyle shifted toward agrarian living.


So why have kitties stayed wilder? The genome-mappers theorize 
it’s because house cat populations have continued to interbreed 
with wild cats. Also, humans’ “cat fancy”—meaning, our fanaticism 
about creating weird cat breeds—only began in the last 200 or so years.


They came for the mice, stayed for the food scraps, and whenever 
it suited, kept cuddly with the cats from the other side of the granary. 
In other words, not only are cats still mostly wild, but they pretty 
much tamed themselves. Maybe that means humans are “cats’ best friend.”
Photo by Flickr user Guyon Morée (image has been cropped).

qz.com

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