Cats are an extreme outlier among domestic animals

Cats are an extreme outlier among domestic animals

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Scientists tracked cat genetics partly by studying the evolution of the “blotched tabby,” pictured here in excruciatingly cute detail.


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People who live with cats like to joke about how these small fuzzy creatures are still wild, basically training us rather than the other way around. Now a new genetic study of ancient cat DNA reveals that we are basically right. Cats were not domesticated in the same way dogs, cows, pigs, and goats were. They have lived among us, but it wasn’t until very recently that we began to change them.

Unlike dogs, whose bodies and temperaments have transformed radically during the roughly 30,000 years we’ve lived with them, domestic cats are almost identical to their wild counterparts—physically and genetically. House cats also show none of the typical signs of animal domestication, such as infantilization of facial features, decreased tooth size, and docility. Wildcats are neither social nor hierarchical, which also makes them hard to integrate into human communities.

Yet it’s impossible to deny that cats are tame. We know that humans have lived with cats for at least 10,000 years—there’s a 9,500 year-old grave in Cyprus with a cat buried alongside its human, and ancient Egyptian art has a popular motif showing house cats eating fish under chairs. Today, cats still share our homes and food, and for thousands of years they have worked alongside farmers and sailors to eradicate vermin. If we haven’t domesticated cats, what exactly have we done to them?

Cats on the high seas

To find out, University of Leuven geneticist Claudio Ottoni worked with a large international team of researchers to analyze the mitochondrial DNA of over 200 ancient and modern cats, spanning the past 9,000 years. Mitochondrial DNA is inherited unchanged solely from the mother, and it is often used to trace the ancestry of different species.

Writing in Nature Ecology & Evolution, Ottoni and his colleagues report that five distinct clades of ancient cats rapidly spread outward from relatively small origin points. Over millennia, the clades from Egypt and Southwest Asia began to dominate the world. Mostly this was due to the spread of agriculture. Farming practices that began in the Levant and Western Asia took hold elsewhere, attracting rodents to grain stores. That, in turn, attracted wildcats, who eventually joined farming communities as companions—just as ancient dogs had joined hunting parties in the Paleolithic.

Then the researchers started to see weird data points, like an Egyptian cat at a Viking sea port during the Middle Ages, and Asian cats at a Roman Red Sea port during the height of the Roman Empire.

This map shows the locations of domestic cat species in the modern world. Note that the two most widespread lineages begin in Egypt (yellow) and southwest Asia (purple).

This map shows the locations of domestic cat species in the modern world. Note that the two most widespread lineages begin in Egypt (yellow) and southwest Asia (purple).

Nature

They realized that many of these cats were spreading along shipping routes. During classical antiquity, ships captains always kept a cat aboard to remove vermin. By the medieval period, it was unlawful in some places to sail without a ship’s cat. As time went on, these cats escaped in ports far from home. There, they would interbreed with local cats. Eventually, the genes of some cat clades began to win out over others.

Medieval cats

Apparently Egyptian cats were especially popular, perhaps because of their friendly dispositions. The researchers note that the world’s obsession with Egyptian cats was so intense that it became a political issue, and a “local ban on cat trading [was] imposed in Egypt as early as 1700 BCE.” Still, Egyptian cats continued to “spread to most of the Old World.” Over time, Mediterranean house cats were all from the Egyptian clade.

Though these cats traveled the world with humans, they were never properly domesticated. More specifically, humans did not control their breeding. The researchers report that house cats often mated with local wildcats. Even when cats were part of farms or ship crews, they moved between the human world and the wilderness.

Ottoni and his colleagues found no evidence of humans breeding cats until the Middle Ages. Possibly the first human-created cat breed was the “blotched tabby,” a cat whose tabby stripes create whorls or spots. Previous researchers had identified the genes responsible for the blotched tabby mutation, so it was easy to track.

Blotched tabbies don’t exist in the wild, and the rise of this color pattern marks an important turning point in cat domestication. For the first time in our long history of cat companionship, humans took charge of cat breeding. At that moment, cats became more like other domestic animals. But there is still one important difference: time. Humans have been intermittently guiding cat breeding for less than 1,000 years. But other domestic animals, like dogs and goats, have been under our control for many millennia.

Arguably, we are at the dawn of cat domestication. Today’s wildcats and house cats are still virtually the same. But in 8,000 years, we might have as many breeds of domestic cats as we do dogs. Imagine having a golden retriever-sized cat, with the same sunny disposition. Tomorrow’s cat lovers might be living with baby-faced tigers or ultra-fluffy purse cats who look like kittens forever.

Or maybe cats will continue to defy domestication. They could carve out a place as one of the only animals to befriend humans without ever falling completely under our control.

Nature Ecology & Evolution, 2017. DOI: 10.1038/s41559-017-0139 (About DOIs).

TECH|SCI

via Ars Technica https://arstechnica.com

June 19, 2017 at 04:05PM

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