>Why are Humans and Dogs so Good at Living Together?

>
Dogs have a special chemistry with humans that goes back many tens of thousands of years. Researchers investigated this special evolutionary relationship from a number of different angles. Their results are surprising.

The social unit
Domestic dogs are descended from wolves so recently that they remain wolves in all biological essentials, including their social behavior. Wolf packs have some intriguing parallels with human families:

They are territorial.
They hunt cooperatively.
Pack members are emotionally bonded and greet each other enthusiastically after they have been separated.
In a wolf pack, only the alpha male and female are sexually active even though other pack members are sexually mature.

The social adaptations of dogs and humans are similar enough that dogs can live perfectly happy lives surrounded by humans and vice versa. Dogs are pampered with the best of food and medical care, frequently sleeping in their owners’ comfortable beds.

A family member
Why do people lavish so much care on a member of an alien species? A short answer is that on an emotional plane, families do not see the dog as alien. According to John Archer (1) of the University of Central Lancashire, who has conducted a detailed study of dog-human relations from an evolutionary perspective, about 40% of owners identify their dog as a family member reflecting social compatibility between our two species.

Dogs are extraordinarily attentive and have an uncanny ability to predict what their owners will do, whether getting the dog a meal or preparing to go on a walk. Experiments show that dogs and wolves can be astute readers of human body language using the direction of our gaze to locate hidden food (2) a problem that is beyond chimps.

Dogs also seem attuned to the emotional state of their masters and express contrition when the owner is annoyed, for example. Otherwise, the capacity to express affection -unconditionally – makes the dog a valued “family member.”

Domesticating each other?
Dogs were the first domestic animal with whom we developed a close association. Mitochondrial DNA research suggests that most domestic dogs have been genetically separate from wolves for at least 100,000 years so that we have associated with dogs for as long as we have been around as a species (Homo sapiens). Indeed, some enthusiasts, including Colin Groves of the Australian National University, in Canberra, believe that our success as a species is partly due to help from dogs (3).

According to Groves: “The human-dog relationship amounts to a very long lasting symbiosis. Dogs acted as human’s alarm systems, trackers, and hunting aides, garbage disposal facilities, hot water bottles, and children’s guardians and playmates. Humans provided dogs with food and security. The relationship was stable over 100,000 years or so, and intensified in the Holocene into mutual domestication. Humans domesticated dogs and dogs domesticated humans.”

Relying on dogs to hear the approach of danger and to sniff out the scent of prey animals, our ancestors experienced a decline in these sensory abilities compared to other primates. This conclusion is confirmed by shrinkage of brain regions devoted to these senses (the olfactory bulb and lateral geniculate body).

During the long period of our association, dogs brains have shrunk by about 20 percent, typical for animals such as sheep and pigs who enjoy our protection. Domesticated animals undergo tissue loss in the cerebral hemispheres critical for learning and cognition. If we relied on dogs to do the hearing and smelling, they evidently relied on us to do some of their thinking.

If Groves is correct that dogs have domesticated humans, then the human brain would also have gotten smaller. Surprisingly, human brains have actually shrunk, but by only a tenth, suggesting that dogs got more out of the deal than we did.

By Nigel Barber, Ph.D.

1. Archer, J. (1997). Why do people love their pets. Evolution and Human Behavior, 18, 237-259.
2. Udell, M. A. R., Dorey, N. R., & Wynne, C. D. L. (2008). Wolves outperform dogs in following human social cues. Animal Behaviour, 76, 1767-1773.
3. Groves, C. P. (1999). The advantages and disadvantages of being domesticated. Perspectives in Human Biology, 4, 1-12.

Source

>The Origin of the Cat

>The Near Eastern wildcat began tagging along with humans on their journeys 10,000 years ago in the Fertile Crescent, according to a new study.

The map shows the historic distribution of the five species of related wildcats, including the Near Eastern wildcat, F.s. lybica. Researchers pinpointed the ancestor of domestic cats by comparing DNA of several wildcat subspecies, including a type of European wildcat pictured above.

Top photograph courtesy Ewan Macdonald, bottom map courtesy Science.

Some say that there are two kinds of people in the world: dog people and cat people. While I don’t want to foster any kind of segregative animosity between fellow humans, it does seem to me that dogs, despite their fewer numbers as pets, tend to have the bigger mindshare. Dogs, not cats, are described as man’s best friend, and you hear of dog-related genetics a fair bit more than you do cat-related science. Not today though.

The reason for this disparity is that although there are hundreds of different varieties of domesticated cats, they don’t show the same spread of sizes and shapes we see in dogs. (Apparently, no one other than me thinks the idea of a Great Dane-sized cat is a good one.) What we do know is that cats and humans have lived together for almost 10,000 years. The earliest evidence of cats and humans together was found in Cyprus and dated at around 9,500 years ago. As to the origins of these early domestic cats, not a huge amount has been known. There are a number of subspecies of Felis silvestris in the wild: F. s. silvestris (Europe), F. s. lybica (Africa and the Near East), F. s. ornate (Middle East and Central Asia), and possibly F. s. bieti (China, although some argue this is a separate species). So which one of these groups did the world’s most numerous pets derive from? A new multinational research effort has found the answer, and it’s published in Science online today.

Carlos Driscoll and his colleagues across the world have collected DNA samples from almost 1,000 different individual cats and looked at different genetic markers to identify common ancestry patterns between domestic cats, purebreds, and wild cats. The data they gathered shows that domestic and purebred cats fall into the same clade as wildcats from the Near East, which matches up well with the archaeological data from Cyprus.

The researchers also worked out the approximate age of the species by looking at the genetic sequences with respect to the rate of mutation in order to calculate a molecular clock. It appears that there were five distinct maternal lineages within the domestic cat clade, as early as 100,000 years ago, predating any evidence of human domestication by an order of magnitude. These lineages all appear within the population of domestic cats.

So there you have it: your house cat, just like our modern civilization, most of our grain crops, and the majority of our domesticated livestock has its origins in the Fertile Crescent.

By Jonathan M. Gitlin.

source