Who were the ancestors of the modern cat?

Genomic fingerprinting of the DNA of feral cats from around the world has clarified the cats' genealogy, revealing some unusual periods of migration in their past

The cats, elegant and mysterious, deceive not only those who share a couch with the little ones, but also scientists who are trying to find out the origin and development of their older cousins. Where did the modern cat family develop? Why and when did they leave their home and cross continents in their wanderings? How many species are there actually, and which species are closely related?

The experts agree, in general, that the cat family (Felidae) has 37 species, but they have also offered dozens of different proposals for the classification of the cat species: some classify them into only two genera (genera) and some classify them into 23 genera. It's hard to tell, because underneath the fur, they look like big cats, medium cats and small cats. Even an expert may have difficulty distinguishing between a tiger's skull and a lion's skull, and attempts we have made in the last 20 years to sort the cats into genetically distinct groups have also been unsuccessful.

However, thanks to the breakthrough of the human genome project and the development of efficient technologies for DNA scanning, recent progress has also been made in determining the gene sequence of animals, which has given us several important research tools. Relying on the innovative techniques, the two of us, with the help of colleagues from other research institutions, constructed the first clear family tree of the cat family.

We compared the exact order in which 30 certain genes appear in the DNA of each of the cat species alive today, and used it to draw the branches of the tree. Then, in order to find out when each branch split, we used fossils whose age is known with certainty and "molecular clock" analyzes (estimating the time when species split according to the degree of variation of certain genes). The result made it possible to sketch the first image that clearly shows the attribution of cats, of all sizes, among themselves, and from it we learned how and when these top predators settled on five continents.

sense of order

At first glance, the DNA tests revealed that the 37 species tend to cluster in eight separate clusters or "lineages". We were intrigued and encouraged by the fact that the eight groups defined based on the molecular analysis alone matched other observations, such as shared morphological, biological, and physiological characteristics unique to each group.

For example, one lineage includes all the big roaring cats (the lion, tiger, tiger, jaguar, and snow leopard). Their tongue bone, which is one of the neck bones that support the tongue, is not all bony, so it allows them to roar. This group also includes the clouded leopard and the Bornean clouded leopard, which are lesser-known, medium-sized cats with beautiful checkered fur. Since the structure of their neck bones is slightly different, they cannot roar.

Comparing gene sequences led to the identification of the lineages and the arrangement of the splits, and also, based on calibration with fossils, to determine the time when they occurred. But we needed two more pieces of information to complete the picture and find out where the cats came from and how they spread around the world. First, we defined the distribution of all species living today and where fossil remains of their ancestors were found. Then we observed the world of cats through the eyes of geologists who know how to interpret the composition of sedimentary rocks and learn from them about rises and falls in sea level. When the sea level is low, land bridges connect continents and mammals can migrate and occupy new habitats. When the sea level returns and rises, the animals on each of the continents become isolated again. Studies in vertebrates show that isolation on a continent or island provides all the conditions for genetic differentiation of a population.

Members of such a population can no longer produce offspring with members of another population, contemporaries, even though they are descendants of a species that was close in the past. This distance or reproductive isolation is the hallmark of species definition. Armed with these pieces of the crossword puzzle, we put together a reasonable sequence of cat migrations throughout history.

Based on the fossils alone, most researchers agree that a cat called Pseudaelurus, which lived in Europe 9 to 20 million years ago, is the last common ancestor of cats (Pseudaelurus was not the first cat.

About 35 million years ago there were already large saber-toothed cats, Nimravids, but almost all their descendants became extinct). However, the molecular studies we did recently suggest that all of today's cats originated from one of the various Pseudolaurus species, a species that lived in Asia about 11 million years ago. Although we do not know what the exact biological species of that cat ancestor was, we believe that a certain pair of cats from this ancient group were "Adam and Eve" of today's 37 species of cats.

On the road

The first group split from this mysterious Asian cat, about 10.8 million years ago, and from it grew the panther lineage, which today includes the big roaring cats and the two species of clouded tiger. The second split, which also happened in Asia about 1.4 million years later, gave rise to the cat lineage of the Borneo Bay, which today includes three species of small cats that evolved in Southeast Asia and still live there. In the next split from the original group, the caracal lineage was founded, which today is represented by three medium-sized species whose ancestors moved to Africa 8 to 10 million years ago in the first intercontinental migration. In those days, the sea level was 60 meters lower than it is today, and Africa was connected to the Arabian Peninsula by land bridges at both ends of the Red Sea, which allowed immigration to Africa.

Cats migrate by nature because they have a behavior pattern that requires dispersal in each generation. When young males (and sometimes females too) grow up and become adults, they are forced to leave the place where they were born. And so, over the years, when the cat population grows, it needs more and more areas to spread out. This behavior, it and the compulsion to follow migrating prey species, explain, one must speculate, what motivated the cats to migrate away. They are also very talented predators, and soon discover new areas that happen to be in their path. It is therefore no wonder that the cats are successfully penetrating untapped territories.

As Asian cats began to move into Africa, they also dispersed throughout Asia and crossed the Bering Land Bridge into Alaska. Then, when the cats were already dawning prey across Asia, Europe, Africa and North America, the sea level rose and the continents separated. Due to the isolation and changing habitats, 20 new species have developed.

In North America, the ocelot and lynx lineages split from the first immigrants about 8 and 7.2 million years ago, respectively. The ocelot lineage eventually split into two species and the schooner lineage into four species. The puma lineage split about 6.7 million years ago, and from it grew the puma (or mountain lion), the jaguaron (a wild cat that lives in Central and South America) and the American cheetah. Fossil remains of all these species, found in deposits in America, firmly establish their origin in the Western Hemisphere.

Two to three million years ago, a new ice age caused the oceans to retreat again, a retreat that was enough, and in continental drift, to connect the two continents of the Americas at the Isthmus of Panama. Some cats took advantage of the opportunity, migrated south and found a continent where there are no predators of whales (such as bears, dogs, cats, skunks, etc.). Until then, South America had been isolated from the northern continent for tens of millions of years and had many marsupials, some of them successful predators. But when the cats arrived from the other side of Panama, they became the ultimate predators: large, agile, intelligent, cruel and deadly. The more modest pickpockets had no chance of successfully competing with them. Almost all native marsupials soon gave way to migratory predators such as ocelot cats, which continued to diverge in their new home and create seven new species that are still found in South America.

When the last ice age subsided, about 12,000 years ago, the thick layers of ice that covered all of Canada and the northern United States began to melt. The frozen wasteland of North America was for forests and grassy steppes. After the Great Thaw, a happy disaster suddenly occurred, 40 mammal species over North America.

The Pleistocene extinctions, as they are called, wiped out 75% of the large animals that lived there. Mammoths, mastodons, coyotes, great short-snouted bears, giant ground sloths, American lions, saber-toothed tigers, cougars, and cheetahs all disappeared from North America. Cheetahs were saved from extinction because a few million years earlier, when the sea was still low, some of their ancestors returned to Asia and then to Africa. The cougars escaped total extermination thanks to the shelter some of them found in South America, and returned to colonize North America after many generations. The other species did not return.

The journey continues

Around the same time that cheetahs crossed the Bering Strait and returned from America to Asia, the ancestors of the tiger cat and domestic cat lineages renounced their American roots, crossed the Bering land bridge, and moved to Asia. They did, a dynasty prospered
The tiger cats and the split into the Asian tiger cat and four other small species that are found today in India (common tiger cat), Mongolia (palas cat), Indonesia (flat-headed tiger cat) and several other places in Asia (tiger fish cat). Back in Asia at that time, the big roaring cats, members of the panther lineage, spread over much wider areas than before.

Large tigers, about 320 kilograms in weight, were distributed throughout Southeast Asia (India, Indochina, the continental shelf of Sunda, and China), while in northern Central Asia and in the west, snow tigers adapted to the heights of the Himalayas and the Altai Mountains.

Tigers were widespread not only in Asia but also in Africa, where they are still found today. The lions and jaguars migrated to North America towards the end of the Pliocene period, three to four million years ago.

Although in the Pleistocene extinctions these two species perished in North America, the jaguars fled early to South America and the lions, who also migrated to Africa at the same time, found a more hospitable continent than Europe, Asia and North or South America. The king of animals still survives in Africa and today about 30,000 lions live there. In Asia, lions are almost completely extinct. Only one tiny population of about 200 individuals survived, members of the Sharim breeding, in the Gir Forest Reserve in the Gujarat province of western India.

Our genetic analysis also revealed that tigers were almost extinct in the past. About 73,000 years ago, the great eruption of the Toba volcano in Borneo destroyed dozens of mammal species in East Asia, including a population of tigers that was spread over large areas. A very small group of tigers survived and they repopulated the area. Indeed, the genetic similarity of their modern descendants indicates that most of the population did not survive the volcanic eruption, and only one small group that survived continued the lineage. Like the cheetahs and cougars in North America, the tigers survived by the skin of their teeth.

And to the living room

The last act in the cat's journey from the jungle to our living room began in the thick forests and vast deserts around the Mediterranean basin. There, a handful of small cat species (less than 10 kilograms in weight) evolved and slowly appeared: the East Asian swamp cat, the Middle Eastern sand cat, the African black-footed cat, and a common wild cat species with four subspecies (European, Central Asian, Eastern Middle and Chinese). With one subspecies of that wild cat, one of the most successful experiments in history began - the domestication of the cat. A wide-ranging study of the molecular genetics of domestic and feral cats worldwide by Carlos Driscoll, a PhD student at the University of Oxford, has shed light on this process. All domestic cats carry genetic imprints that match those of Asian wild cats from Israel and the Middle East. Today we believe that cats were domesticated several times, all in the Fertile Crescent region, 8,000 to 10,000 years ago, at a time when nomadic human tribes began to gather in small villages - the first agricultural settlements.
The first farmers raised wheat and barley and wild cats from the area, perhaps attracted by the abundance of rodents in the barns, probably offered themselves as reluctant companions who made a living by smuggling the pest rodents. The wild cats became domesticated, proliferated and multiplied and linked their fate with the fate of humans.

Humans eventually began to migrate as well. At first on foot, then in carts and then in large ships, and with them they also brought their companions, the house cats, everywhere in the world. About 600 million domestic cats live in the world today. According to the definitions of nature conservation organizations in the world, this is the only cat species that is practically not in danger of extinction. In the 19th century cat owners were already selectively breeding their pet cats and breeding fancy breeds. The American Cat Fanciers Association lists 41 official cat breeds, from the Maine Coon and Siamese to the Persian and Korat, all of which have a lineage leading to the cradle of human and feline culture in the Fertile Crescent.
The evolutionary story that emerges from our research in the cat family heralds the birth of a new field - "genomic prehistory", with us, as with cats, the patterns of genetic variations bear evidence of kinship, migration, survival and spread all over the planet.

Writer: Stephen G. O'Brien and Warren A. Johnson. Published in "Scientific American" magazine.