A history of the domestic cat

Nicholas Wade, Science Writer at the New York Times, provides a further history of cats. This time it is focused only on house cats. Like his previous story, this report is also based on DNA analysis. [The previous publication of general history of cats is found at Where did cats come from?.]

June 29, 2007

Study Traces Cat’s Ancestry to Middle East

By NICHOLAS WADE

Some 10,000 years ago, somewhere in the Near East, an audacious wildcat crept into one of the crude villages of early human settlers, the first to domesticate wheat and barley. There she felt safe from her many predators in the region, such as hyenas and larger cats.

The rodents that infested the settlers’ homes and granaries were sufficient prey. Seeing that she was earning her keep, the settlers tolerated her, and their children greeted her kittens with delight.

At least five females of the wildcat subspecies known as Felis silvestris lybica accomplished this delicate transition from forest to village. And from these five matriarchs all the world’s 600 million house cats are descended.

A scientific basis for this scenario has been established by Carlos A. Driscoll of the National Cancer Institute and his colleagues. He spent more than six years collecting species of wildcat in places as far apart as Scotland, Israel, Namibia and Mongolia. He then analyzed the DNA of the wildcats and of many house cats and fancy cats.

Five subspecies of wildcat are distributed across the Old World. They are known as the European wildcat, the Near Eastern wildcat, the Southern African wildcat, the Central Asian wildcat and the Chinese desert cat. Their patterns of DNA fall into five clusters. The DNA of all house cats and fancy cats falls within the Near Eastern wildcat cluster, making clear that this subspecies is their ancestor, Dr. Driscoll and his colleagues said in a report published Thursday on the Web site of the journal Science.

The wildcat DNA closest to that of house cats came from 15 individuals collected in the deserts of Israel, the United Arab Emirates, Bahrain and Saudi Arabia, the researchers say. The house cats in the study fell into five lineages, based on analysis of their mitochondrial DNA, a type that is passed down through the female line. Since the oldest archaeological site with a cat burial is about 9,500 years old, the geneticists suggest that the founders of the five lineages lived around this time and were the first cats to be domesticated.

Wheat, rye and barley had been domesticated in the Near East by 10,000 years ago, so it seems likely that the granaries of early Neolithic villages harbored mice and rats, and that the settlers welcomed the cats’ help in controlling them.

Unlike other domestic animals, which were tamed by people, cats probably domesticated themselves, which could account for the haughty independence of their descendants. “The cats were adapting themselves to a new environment, so the push for domestication came from the cat side, not the human side,” Dr. Driscoll said.

Cats are “indicators of human cultural adolescence,” he remarked, since they entered human experience as people were making the difficult transition from hunting and gathering, their way of life for millions of years, to settled communities.

Until recently the cat was commonly believed to have been domesticated in ancient Egypt, where it was a cult animal. But three years ago a group of French archaeologists led by Jean-Denis Vigne discovered the remains of an 8-month-old cat buried with its human owner at a Neolithic site in Cyprus. The Mediterranean island was settled by farmers from Turkey who brought their domesticated animals with them, presumably including cats, because there is no evidence of native wildcats in Cyprus.

The date of the burial far precedes Egyptian civilization. Together with the new genetic evidence, it places the domestication of the cat in a different context, the beginnings of agriculture in the Near East, and probably in the villages of the Fertile Crescent, the belt of land that stretches up through the countries of the eastern Mediterranean and down through what is now Iraq.

Dr. Stephen O’Brien, an expert on the genetics of the cat family and a co-author of the Science report, described the domestication of the cat as “the beginning of one of the major experiments in biological history” because the number of house cats in the world now exceeds half a billion while most of the 36 other species of cat, and many wildcats, are now threatened with extinction.

So a valuable outcome of the new study is the discovery of genetic markers in the DNA that distinguish native wildcats from the house cats and feral domestic cats with which they often interbreed. In Britain and other countries, true wildcats may be highly protected by law.

David Macdonald of Oxford University, a co-author of the report, has spent 10 years trying to preserve the Scottish wildcat, of which only 400 or so remain. “We can use some of the genetic markers to talk to conservation agencies like the Scottish Natural Heritage,” he said.

I am not sure if Mr. Wade just has a thing about cats or if he gets a journal of research reports that includes such cat research. No matter, I am enjoying his reports.

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If you find this interesting, you will find Nicholas Wade's book Before the Dawn: Recovering the Lost History of Our Ancestors about DNA research into how human beings evolved absolutely fascinating. DNA evidence shows that there were two different wave of human exodus out of Africa, first by Homo Erectus about 1.8 million years ago, becoming Homo Erectus and Neanderthal Man. While these groups were tool using, they did not have full speech of the kind demonstrated by Homo Sapiens. Full speech developed in Africa within the last hundred thousand years, and the first Exodus of true humans from Africa to the rest of the world occurred roughly 50,000 years ago.

DNA analysis suggests that they left Africa by a route from what today is the Horn of Africa and moved into what is today Yemen. The analysis also shows the routes taken by various groups from Africa to Australia, Asia, Europe, and the Americas. Geology and Climatology show what routes they took. Evolution theory suggests that the two evolutionary pressures that caused the differentiation of the races were climatic uncertainty and (the more important one) the standards of beauty each society developed. Both the Asian race and the Caucasian race developed lighter skin because of the need to get more Vitamin D from the shorter periods of sunlight in the far North. Very interestingly, the DNA results tend to agree with the studies of language development over the same periods of time and in the same places.

The book is highly readable and easy to follow, although there is so much in it you will take your time going through it. This is not the early history you may have read before the year 2002 when the human genome was mapped. Suddenly we have entirely new sources of information to compare against anthropology, geology and linguistics among other disciplines, to the real benefit of all the sciences. We also have Nicholas Wade, a writer who can understand how this all fits together and explains it clearly. It's well worth your reading time.

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Other suggested books are

• How Brains Think: Evolving Intelligence, Then and Now
  by William H. Calvin
  and
• Guns, Germs, and Steel: The Fates of Human Societies, New Edition
  by Jared Diamond.
• The Great Transformation: The Beginning of Our Religious Traditions
  by Karen Armstrong.

These books, written independently, will provide a relatively coherent story of how current human society came into being. Start with "Before the Dawn" first, though. It puts the other three into a much clearer perspective and should make them more enjoyable to read.

Unfortunately, Cats do not play a prominent role in any of them. If house cats could read, they would demand the attention which everyone and every cat knows they deserve.

What does it mean to be a Human Being? What's unique?

Sharon Begley gives us some recent findings on how Humans evolved into what we are today. It is a rather lengthy article in Newsweek (Mar 19, 2007 edition), and entirely worth reading and rereading.

The title tells what the story is about. What has science found recently, outside new sets of bones and the geology in which they are buried, that provides us now information about the evolution of Homo Sapiens out of the the last creature that we know from DNA that we share as an ancestor with Chimpanzees.

Whatever that creature was, the DNA of both Homo Sapiens and of Chimpanzees have been changing for approximately 5 to 6 million years since then. Humans have learned to walk upright freeing our hands for other tasks, to talk, and for some reason, we have lost our fur. This last is particularly interesting, and the timing, if not the reason, is indicated in the DNA of lice.

It seems that there are two different types of lice which afflict humans. One is the head louse, an affliction we share with our cousin the Chimpanzee, since the environment the head lice live in is the fur or hair on our bodies. Humans, however, are also afflicted by a second type of louse. [No, not my ex-wife or her boyfriends.]The second type is the misnamed body louse.

The environment the so-called body louse lives in is human clothing. DNA shows that only 114,000 years ago the head lice and body lice shared a common ancestor. The body lice appeared when a new environment opened up for them to live in, and that new environment was human clothing (or exo-fur, as I explain to my impatient dogs when I have to put on my clothes and shoes - my exo-fur and paw-covers - before I can take them outside. Need to translate these things into words they might understand, you know.) But that is how louse DNA can point to the time that people began wearing clothes.

Apparently also, there were two waves of human and human-related migrations out of Africa. The first was of Homo Erectus, who left Africa and spread across Eurasia sometime between 1 and 2 million years ago. The second was the wave of Homo Sapiens who left Africa and spread to Eurasia about 66,000 years ago. DNA strongly suggests that Homo Erectus died out and was not an ancestor to Homo Sapiens. See the article for the details.

I'm going to skip writing about the much more complicated human ancestral tree that DNA is suggesting, and skip directly to what fascinates me most.

A curious thing about early Homo species is that they looked quite human early on. "By 600,000 years ago everyone had a big brain, and by 200,000 years ago people in Africa looked like modern humans," says archeologist Richard Klein of Stanford. "But there was no representational art, no figurines, no jewelry until 50,000 years ago. Some kind of cognitive advance was required, probably in language or working memory. But since size hardly changed, the brain change that produced behaviorally modern humans must have been in structure."

The source of such structural changes must come, like every aspect of our physiology, from genes. Combing the genome for genes that emerged just when language, art, culture and other products of higher intelligence did, researchers have found three with the right timing.

The first, called FOXP2, plays a role in human speech and language, but it must do something else in other species, because the decidedly nonverbal mouse has a version of it. Using the standard molecular-clock tactic, Svante Paabo and colleagues at the Max Planck Institute estimate that the human version of FOXP2 appeared less than 200,000 years ago—about when anatomically modern humans stepped onto the world stage—and maybe as recently as 50,000. If so, then it is only humans as modern as those in the last diaspora out of Africa who developed advanced, spoken language. Another gene with interesting timing is microcephalin, which affects brain size. It carries a time stamp of 37,000 years ago, again when symbolic thinking was taking hold in our most recent ancestors. The third, called ASPM and also involved in brain size, clocks in at 5,800 years. That was just before people established the first cities in the Near East and is well after Homo sapiens attained their modern form. It therefore suggests that we are still evolving.

As I recall (and don't ask my source) the first ornaments found in a human grave were placed there about 36,000 years ago. Ornaments such as small items of jewelry have no practical purpose. They have to be symbolic. Note the relationship to brain-size above.

Then let's look at what the human race was doing 6,000 years ago. This was the period of the Sumarian civilization in the Tigris-Euphrates valley where the Sumarians built their cities of Ur, Erich and Kish, created the first writing (Cuneiform script) built the Ziggarats and developed the first law and impressive literature and myths. Karen Armstrong also points out that the major religions all began to develop at this time.

One last thing. If humans learned to speak only after Homo Erectus spread out into Eurasia but before the Homo Sapiens moved out of Africa about 66,000 years ago, then the Humans had a massive advantage over Homo Erectus. They also ate much the same food, so they needed the same lands. It is very likely that they battled over that land, and the social, speaking hominid found it relatively easy to defeat the non-speaking hominid. That would certainly explaian the disappearance of the Homo Erectus. It would be like a modern army with radio communications going up against one without radios.

You will notice that I persist in using the terms "suggests" and "Points to" rather than saying "tells us this was the cause and result." That's because this science is simply associating what the bones tell us, then what the bones associated with the geology tells us, together with what the DNA studies are saying. These associations from different fields of science could each be purely coincidence. But All of them? Are these all just accidental associations that have no common causes? I strongly doubt that.

But I can't prove it on the evidence given - so far.

Sure is fascinating, though, isn't it? What do we get next year? We'll just have to wait and see, won't we.

Where did cats come from?

The NYTimes has a fascinating science article that describes the family tree and prehistoric migrations of cats.

January 6, 2006
DNA Offers New Insight Concerning Cat Evolution
By NICHOLAS WADE

Researchers have gained a major insight into the evolution of cats by showing how they migrated to new continents and developed new species as sea levels rose and fell.

About nine million years ago - two million years after the cat family first appeared in Asia - these successful predators invaded North America by crossing the Beringian land bridge connecting Siberia and Alaska, a team of geneticists writes in the journal Science today.

Later, several American cat lineages returned to Asia. With each migration, evolutionary forces morphed the pantherlike patriarch of all cats into a rainbow of species, from ocelots and lynxes to leopards, lions and the lineage that led to the most successful cat of all, even though it has mostly forsaken its predatory heritage: the cat that has induced people to pay for its board and lodging in return for frugal displays of affection.

This new history of the family, known as Felidae, is based on DNA analyses of the 37 living species performed by Warren E. Johnson and Stephen J. O'Brien of the National Cancer Institute and colleagues elsewhere.

Before DNA, taxonomists had considerable difficulty in classifying the cat family. The fossil record was sparse and many of the skulls lacked distinctiveness. One scheme divided the family into Big Cats and Little Cats. Then, in 1997, Dr. Johnson and Dr. O'Brien said they thought most living cats fell into one of eight lineages, based on the genetic element known as mitochondrial DNA.

Having made further DNA analyses, the researchers have drawn a full family tree that assigns every cat species to one of the lineages. They have also integrated their tree, which is based solely on changes in DNA, with the fossil record. The fossils, which are securely dated, allow dates to be assigned to each fork in the genetic family tree.

Knowing when each species came into existence, the Johnson-O'Brien team has been able to reconstruct a series of at least 10 intercontinental migrations by which cats colonized the world. The cheetah, for instance, now found in Africa, belongs to a lineage that originated in North America and some three million years ago migrated back across the Bering land bridge to Asia and then Africa.

Dr. O'Brien said the cats were very successful predators, second only to humans, and quickly explored new territories as opportunity arose. Sea levels were low from 11 million to 6 million years ago, enabling the first modern cats, in paleontologists' perspective (saber-tooth tigers are ancient cats), to spread from Asia west into Africa, creating the caracal lineage, and east into North America, generating the ocelot, lynx and puma lineages.

The leopard lineage appeared around 6.5 million years ago in Asia. The youngest of the eight lineages, which led eventually to the domestic cat, emerged some 6.2 million years ago in Asia and Africa, either from ancestors that had never left Asia or more probably from North American cats that had trekked back across the Bering land bridge.

Sea levels then rose, confining each cat species to its own continent, but sank again some three million years ago, allowing a second round of cat migrations. It was at this time that the ancestors of the cheetah and the Eurasian lynxes colonized the Old World from the New.

Chris Wozencraft, an authority on the classification of carnivorous mammals, said the new cat family tree generally agreed with one that he had just published in Mammal Species of the World, a standard reference. Dr. Wozencraft, a taxonomist at Bethel College in Indiana, based his classification on fossil and zoological information, as well as on DNA data already published by Dr. O'Brien's laboratory.

Cat fossils are very hard to tell apart, because they differ mostly just in size, and the DNA data emerging over the last decade has helped bring the field from confusion to consensus, Dr. Wozencraft said.

Despite their evolutionary success, most of the large cats are in peril because their broad hunting ranges have brought them into collision with people. "With the exception of the house cat and a few other small cat species, nearly every one of the 37 species is considered endangered or threatened," Dr. Johnson and Dr. O'Brien write in the current Annual Review of Genomics and Human Genetics.

Fewer than 15,000 tigers, cheetahs and snow leopards remain in the wild, they estimate, and pumas and jaguar populations have been reduced to about 50,000 each.

It is especially interesting that the DNA evidence ties back very closely to the limited fossil evidence, and corresponds to the history of the rise and fall of oceans that geologists have determined.

This is a story which could never be told by the anti-evolutionists. Of course, it also confirms my suspicion that house cats are the dominant species on earth. They just let us humans THINK we dominate the world, as we work to provide food and shelter for the cats.