By Dr. Karen Shaw Becker
Cats are among the most popular pets in the world, despite the fact that there's much debate over how domesticated our "domestic" cats really are, as well as how our lovable housemates emerged from ancient wild cats. One relatively new revelation came from researchers with the University of Leuven in Belgium, who analyzed the mitochondrial DNA (which is passed down from mothers to offspring) of 209 ancient cats' remains.
Some of the samples were up to 8,500 years old and came from around the world, including Bulgaria and Romania, Egypt, Spain, Iran, Kenya and Tanzania. By tracking mutations in the DNA, researchers were able to uncover dates and ancestry of the remains, which revealed cats as we know them today likely emerged during at least two separate domestication events.
Modern-Day Domestic Cats Traced Back to Two Regions: South Asia and the Mediterranean
Wild cats from both Near Eastern and Egyptian populations contributed to the gene pool of today's domestic cats, at different times in history, according to the study, published in the journal Nature Ecology & Evolution.1
"While the cat's worldwide conquest began during the Neolithic period in the Near East, its dispersal gained momentum during the Classical period, when the Egyptian cat successfully spread throughout the Old World," the researchers explained. "The expansion patterns and ranges suggest dispersal along human maritime and terrestrial routes of trade and connectivity."2
In other words, two distinct lineages were found. It's thought the cats from South Asia reached Europe around 4400 B.C., while a separate lineage of cats was represented in paintings and mummies found in Egyptian tombs. DNA from the Egyptian cat was widespread by the year 1000, according to the study.3 As for how cats traveled the world, they were likely valued on ships, in villages and in barns because they helped control rodent pests. The researchers wrote:4
"In medieval times it was compulsory for seafarers to have cats onboard their ships, leading to their dispersal across routes of trade and warfare …
… This evidence explains, for example, the presence of the Egyptian lineage ... at the Viking port of Ralswiek (7 [to] 11th century [A.D.]) … Spread of the black rat and house mouse by sea routes as early as the Iron age, documented by zooarchaeological and genetic data, probably also encouraged cat dispersal for the control of these new pests."
The authors noted that directed breeding of cats occurred much later with cats compared to most other domesticated animals, and breeding of the animals for different sizes, colors or body shapes hasn't widely occurred the way it has with dogs. For instance, the DNA mutation that creates blotched coats in tabby cats wasn't seen until the Medieval period.5
It's thought, instead, that certain cats won over humans due to their behaviors rather than their looks. "As the most pronounced genetic changes that distinguish wild and domestic cats are apparently linked to behavior, it is tempting to speculate that the success of the Egyptian cat is underlain by changes in its sociability and tameness," the researchers wrote.6
Ancient Cats Likely Traveled With Mariners, Farmers and Vikings
The DNA analysis — the largest to date of ancient cats — revealed that cats in the Middle East and eastern Mediterranean shared a mitochondrial lineage. The researchers suggested wild cats may have been drawn to early farming communities in the eastern Mediterranean, where grain stockpiles attracted plenty of rodents. The farmers likely appreciated the cats' rodent-catching skills and may have started to tame them.
A shared mitochondrial lineage was also found among Egyptian cat mummies and cats in Bulgaria, Turkey and sub-Saharan Africa from the end of the 4th century B.C. to the 4th century A.D. As mentioned, this same DNA lineage was also found at a 7th to 11th century Viking settlement in northern Germany. It's likely that Vikings and other sailors invited cats onto their ships to help control rodents, furthering the domestication of felines.
There are still many domestication questions to be answered, however, especially since domestic cats continue to interbreed with wildcats in Europe, Asia and Africa to this day.7 One of the biggest questions is whether cats are truly domesticated. In comparing the genome of a domestic cat with a tiger, genes were found in the cat that would make her more likely to approach humans and interact with them, and also to seek rewards.
Differences in genes affecting memory, fear-conditioning behavior and stimulus-reward learning were also noted, which may point to cats being domesticated.8 While overall the genomes of domestic cats have changed very little since splitting from their wild counterparts, it's still possible with sequencing to see markers of more recent domestication.
That being said, there are ways that cats are considerably more "wild" than their fully domesticated canine counterparts. For instance, they've retained much of their hunting abilities in comparison to wild cats, and they don't need to be housebroken — they instinctively know where to "go."
The fact that cats tend to be independent and fairly self-sufficient (cleaning themselves, for instance) adds to the semi-domesticated camp, as does the fact that dogs have about tenfold more molecular signatures of domestication than do cats.9 As for whether semi-domestication is an asset or a detriment to the species, that, too, is up for debate. But for many cat owners, it's their kitty's wild side that they find most lovable of all.