The tuatara, a New Zealand reptile, is the last survivor of an ancient order called Sphenodontia. Its last known relatives are believed to have died out sixty million years ago.

The slow-moving creature hit the news recently because of a discovery made by David Lambert and his colleagues from the Allan Wilson Center for Molecular Ecology and Evolution at Massey University in New Zealand: The tuatara's DNA undergoes 1.56 changes per nucleotide per million years. - the fastest rate of molecular (genetic) evolution observed so far.

That in itself would not be so remarkable except that the tuatara has changed little in 200 million years.

Just how slow is the tuatara?

The apparent paradox was certainly not lost on the researchers. "Of course we would have expected that the tuatara, which does everything slowly -- they grow slowly, reproduce slowly and have a very slow metabolism -- would have evolved slowly. In fact, at the DNA level, they evolve extremely quickly," says Prof. Lambert.

The tuatara, of which there are two known species, is thought by some to resemble a dinosaur. It is believed to have separated from other reptiles in the Upper Triassic Period, 200-225 million years ago.

Its name, which originated in the Maori language, references the row of spines on the back of both sexes, the male's row being more prominent. The males grow to about 1/3 metre in length and weigh about 1 kg. The females are somewhat smaller. Unlike many reptiles, tuataras do not have visible ear openings, and the male tuatara does not have a penis.

According to the Kiwi Conservation Club tuataras have a slow metabolism, even for an exothermic (poikilothermic) animal. They have one of the slowest growth rates of any reptile. They do not reach sexual maturity until about 15 years of age, though they continue to grow until they are about 35. They breed every two to five years. After a gestation period of eight to nine months, the female lays and buries six to ten eggs in a sunny area. The young hatch after 11-16 months.

The tuatara life span averages 60 years but individuals may live over a century. Their diet is insects, lizards, eggs and, chicks. The sheer slowness of the tuatara's growth and reproduction is a source of concern for New Zealand conservationists, because any significant decline in numbers would take along time to reverse itself, even with protection.

How did scientists determine the rate of the tuatara's evolution?

Jennifer Viegas of Discovery News Channel reports that comparing the tuatara's rate of evolution to closely related animals was not possible because its close relatives are all extinct:

For the study, Lambert and his team amplified and sequenced DNA from the bones of 33 ancient tuataras, dating from more than 8,750 years ago to 650 years ago, as well as blood samples from 41 modern individuals.

The tuatara turned out to be changing its DNA faster than such animals as the Adelie penguin, aurochs, Mappin's moa, bison, brown bear, cave bear, cave lion, ox and horse.

How can there be evolution without change?

Ironically, New Zealand biologist Allan Wilson, after whom the center at which Prf. Lambert works is named, had proposed - controversially - forty years ago that "the rate of molecular evolution was uncoupled from the rate of morphological evolution," a position with which Lambert now agrees.

British physicist David Tyler,  comments in his column at Access Research Network,

The paper points out that their findings challenge many hypotheses and notions about evolutionary change. The most substantial conclusion that can be drawn is that it supports the general hypothesis that the rate of molecular evolution is not coupled to the rate of morphological [body form] evolution. But this, of course, challenges the neoDawinian synthesis, which insists on small incremental changes acted on by natural selection.

[ ... ]

The evidence is accumulating that much contemporary evolutionary theory is not supported by data. If you want a prediction arising out of the tuatara research, it is that the gulf between the genome and the development of form will widen, and the association of molecular evolution with morphological evolution will be weakened.

In short, the tuatara's sluggish exterior conceals a swiftly changing genome that never got around to doing anything for two hundred million years. That in turn raises the question, as Tyler notes, of just what influence the genome does have on animal form (morphology) or evolution.

Also, here is another article on problems in molecular evolution: Molecular clock keeps good time - twice a day?

Resources:

Journal article: Rapid molecular evolution in a living fossil." Researchers include Jennifer M. Hay, Sankar Subramanian, Craig D. Millar, Elmira Mohandesan and David M. Lambert, Trends in Genetics. March 2008. (http://dx.doi.org/10.1016/j.tig.2007.12.002)

Abstract: The tuatara of New Zealand is a unique reptile that coexisted with dinosaurs and has changed little morphologically from its Cretaceous relatives. Tuatara have very slow metabolic and growth rates, long generation times and slow rates of reproduction. This suggests that the species is likely to exhibit a very slow rate of molecular evolution. Our analysis of ancient and modern tuatara DNA shows that, surprisingly, tuatara have the highest rate of molecular change recorded in vertebrates. Our work also suggests that rates of neutral molecular and phenotypic evolution are decoupled.

"Tuatara, the fastest evolving animal", EurekAlert, 20 March 2008

Tuatara images from Google

Darwin's theory of sexual selection is widely regarded as explaining how the peacock's magnificent tail evolved. But the theory may not be correct for that very "poster" example, the peacock. As The Design of Life authors explain, sexual selection is Darwin’s explanation for how animals acquire traits that do not help them survive (have no direct adaptive value), and may even hinder their survival:

Consider a stag whose antlers are so large that they are more deadweight than defense. Or a peacock whose large colored tail makes it easy prey. How do such structures evolve? According to Darwin, they evolve because they help to attract mates—they are a form of sexual display. (The Design of Life GN6)

Darwin championed this explanation because, as he wrote to American botanist Asa Gray (April 3, 1860), "The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick!" Why did it make him sick?

Darwin needed to account for  animal traits that do not promote survival, and may even hinder it. Essentially, he had to incorporate an explanation for traits that hinder survival into a theory that attempts to explain traits that promote survival.

His explanation, the theory of sexual selection, has been widely accepted, and is now part of the doctrine of undirected evolution. For example the PBS Evolution Library says:

Peahens often choose males for the quality of their trains - the quantity, size, and distribution of the colorful eyespots. Experiments show that offspring of males with more eyespots are bigger at birth and better at surviving in the wild than offspring of birds with fewer eyespots.

and Berkeley's Evolution 101 says,

Sexual selection is a “special case” of natural selection. Sexual selection acts on an organism's ability to obtain (often by any means necessary!) or successfully copulate with a mate. Selection makes many organisms go to extreme lengths for sex: peacocks (top left) maintain elaborate tails, elephant seals (top right) fight over territories, fruit flies perform dances, and some species deliver persuasive gifts.

His weakness is his strength?

But remember, the peacock must carry his tail whether he gets a hen or not. The tail, produced by the absence of estrogen, is generally agreed to be a deadweight for the cock bird. Mark Ridley observes in the Third Edition of Evolution (Blackwell, 2003):

The peacock's tail almost certainly reduces the male's survival: the tail reduces maneuverability, powers of flight, and makes the bird more conspicuous; its growth must also impose an energetic cost.

In that case, we might expect the generously tailed cock birds to be picked off by predators, leaving their less feathery brethren to mate. Yet that does not happen, not even in nature, where wild peacocks are as well endowed with tails as tame ones.

Evolutionary psychologist Geoffrey Miller of University College, London, thinks he has an answer:

The peacock's tail is not just an arbitrary outcome of sexual selection. It's there because it's costly, which means only those fit, healthy, strong peacocks can afford to carry around those tails.

This hypothesis, called Zahavi's handicap or the "handicap principle," states:

An individual with a well developed sexually selected character [such as a peacock's flashy tail] is an individual which has survived a test. A female which could discriminate between a male possessing a sexually selected character, from one without it, can discriminate between a male which has passed a test and one which has not been tested. Females which selected males with the most developed characters can be sure that they have selected from among the best genotypes of the male population. (Amotz Zahavi (1975)

So, according to this thesis, the hen bird realizes that the tail is a handicap for the cock bird, but, to the extent that he bears it in a cocksure manner, she also realizes that he must be a healthy mate.

Not only that but, according to Matt Ridley, the tail prevents "low quality" males from representing themselves as strong, because they do not have such a tail to drag about:

The handicap acts as an indicator of genetic quality and has to be costly to guarantee that signalling is honest: otherwise low quality males could equally well advertise and females would be unable to distinguish between them.

So, during the hyperactive mating season, not only does the hen bird make a decision about the relative fitness of the cock birds, but she accounts for their handicaps and determines that they are not a false signal. Or if not the hen bird herself, then what is doing the calculating? Her selfish genes? Do we have any evidence that such selfish genes exist, other than as a hypothetical support to an otherwise shaky theory?

Or, alternatively, the researchers may envision a complex but blind mating algorithm which simply produces this outcome. But that does not explain why an agile, tailless peacock does not simply mount more peahens. Against such a move, a mere algorithm is powerless.

Zahavi's handicap sounds like an argument put forward to protect the original theory of sexual selection from falsification, rather than an argument that addresses the nature of the birds themselves. Indeed, one problem with arguments like Zahavi’s handicap is that they render the theory of sexual selection unfalsifiable. If a peacock whose tail has fallen out due to a hereditary disorder proves agile enough to mount most of the hen birds and pass on his "tailless" trait, the theory of sexual selection can easily be altered to accommodate his success.

But in that case, what about the "costly handicap"? What becomes of all the elaborate calculations that the hen birds are supposed to be doing for the good of the gene pool? If the theory of sexual selection means to say only that birds somehow choose mates and eggs are laid, no one will dispute it. But if the theory is intended to shed light on peacocks' appearance and behaviour, it must say something explicit enough to be falsifiable by a pattern of events that does not conform to it.

Of course, all these proposed explanations depend on the assumption that the female bird (the peahen) actually makes a decision based on the size and beauty of her prospective mate's tail. But does she?

Well, does she or doesn't she?

Recent research suggests that she doesn't. Jennifer Viegas, of Discovery Channel News, reports on the work of Mariko Takahashi of the University of Tokyo and her colleagues on this very question (March 26, 2008). Their findings contradict earlier reports that the peahens are impressed by brilliant tails.

From spring 1995 through spring 2001, the researchers observed peafowl (the correct name for the species) mating at Izu Cactus Park on the Izu Peninsula, about 100 kilometres southwest of Tokyo. They found that the peahens do not pay much attention to the peacocks' feathered finery. As Viegas reports,

The determination throws a wrench in the long-held belief that male peacock feathers evolved in response to female mate choice. It could also indicate that certain other elaborate features in galliformes, a group that includes turkeys, chickens, grouse, quails and pheasants, as well as peacocks, are not necessarily linked to fitness and mating success. [ ... ] Across the board, the researchers were unable to link the elaborateness of a peacock's train with his mating success. In fact, Takahashi and her team found little train variance among males in the population they studied. They also couldn't detect any link between a particular male's fitness and his train.

The new research suggests that the peacock's shrill mating scream attracts more attention from peahens than his fanned tail display. However, the tail may attract attention during the peacock's "shivering" display. According to Takahashi and colleagues:

Shivering is a display in which a peacock shows and shakes his train directly towards a visiting female at close range, producing a rustling noise (e.g. Ridley et al. 1984).During a female visit, males sometimes performed more than 20 shivering bouts. Each bout lasted 1 to >400 s and consisted of quick changes in the intensity of the noise produced; these changes were termed ‘shivers’ and were generated approximately twice per second.

British physicist David Tyler quotes Takahaski's dissent from the traditional sexual selection explanations:

To date, the peacock's train has been proposed not only as a target of current female choice (e.g. Petrie et al. 1991), but also as an indicator of good genes (Petrie 1994). However, there may be at least four problems with these hypotheses. First, male train morphology seems not to be the universal cue of choice because there is evidence both for and against the effect of male train morphology on male mating success. [. . .] Second, the ways in which females assess male trains (unless females have the ability to count eyespots per se) have been questioned repeatedly but have not been fully investigated. Third, there is no consensus on which traits characterize males with the most elaborate trains. [. . .] Fourth, to our knowledge, mate choice based on a male plumage ornament that is under oestrogen control is very rare.

Takahashi suggests that at one time the tail impressed peahens but is now "obsolete":

We propose that the peacock's train is an obsolete signal for which female preference has already been lost or weakened, but which has none the less been maintained up to the present because it is required as a threshold cue to achieve stimulatory levels in females before mating and/or it is maintained as an unreliable cue [. . .].

Tyler observes,

The alleged amazing powers of natural selection are much diminished as a result of these findings. The argument that it is "powerful enough" to maintain the feather display against the negative effects of attracting predators must be dropped. Furthermore, it appears not powerful enough to remove the display when it becomes an "obsolete signal". Darwinists need to think very hard about the way they do science. This is a clear example of how a Darwinian hypothesis has become accepted as scientific fact, yet now has been disproved by some rigorous empirical research. This is a falsified prediction. This means that numerous textbooks and web sites need to be revised. More importantly, Darwinists should cease giving the impression that they have the keys to understand the natural world. So much of this 'understanding' is like peacock feathers - lots of show and no substance. Richard Dawkins extols Darwinism as a beautiful theory, but whenever we look closely, it fails to account for the observed data.

The study, its abstract, and other resources

Title: Peahens do not prefer peacocks with more elaborate trains Mariko Takahashi, Hiroyuki Arita, Mariko Hiraiwa-Hasegawa and Toshikazu Hasegawa Animal Behaviour, 75(4), April 2008, 1209-1219 | doi:10.1016/j.anbehav.2007.10.004

Abstract: The elaborate train of male Indian peafowl, Pavo cristatus, is thought to have evolved in response to female mate choice and may be an indicator of good genes. The aim of this study was to investigate the role of the male train in mate choice using male- and female-centred observations in a feral population of Indian peafowl in Japan over 7 years. We found no evidence that peahens expressed any preference for peacocks with more elaborate trains (i.e. trains having more ocelli, a more symmetrical arrangement or a greater length), similar to other studies of galliforms showing that females disregard male plumage. Combined with previous results, our findings indicate that the peacock's train (1) is not the universal target of female choice, (2) shows small variance among males across populations and (3) based on current physiological knowledge, does not appear to reliably reflect the male condition. We also found that some behavioural characteristics of peacocks during displays were largely affected by female behaviours and were spuriously correlated with male mating success. Although the male train and its direct display towards females seem necessary for successful reproduction, we conclude that peahens in this population are likely to exercise active choice based on cues other than the peacock's train.

Paper: A version of the  paper by Takahashi et al on this subject, online.

Other resources:

 General Peafowl Information

How the peacock's colours are produced. From New Scientist: "a lattice of melanin rods and keratin on the outer layer of each barbule forms a two-dimensional photonic crystal structure. The number and spacing of the rods determines the colour of the barbule and its intensity (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2133313100)."

Domestication of the peacock

And finally, just for fun: Lonely British peacock romances a petrol (gas) pump (Times, June 17, 2006) "Ornithologists believe that Mr P is confused by the clicking sounds of the pumps, which resemble the cries of a broody peahen. ... His two brothers are also showing signs of confusion when it comes to finding a mate. One appears to have a crush on the family cat, and the other has been seen attempting to mate with a garden light."

Many feral dogs (wild dogs) are actually descendants of domesticated breeds. Contrary to what is commonly thought, feral dogs whose recent ancestors were domestic animals can adapt quite well to life without human companions.

They do not always depend upon human garbage for their food supply. Many feral dogs become adept hunters, and they may cover a range of 130 km². They do not depend only on meat for their diet. They also eat both cultivated and wild vegetables and fruit. It's not uncommon for feral dogs to revert to a "pack" lifestyle as well. Pack behaviours may include shared rearing of pups and nocturnal (dusk to dawn) activity.

If feral dogs' recent ancestors were domestic breeds, they at first form motley packs of various shapes and sizes, depending on the mixture of breeds from which they derive. But if they remain free and reproduce, after a few generations of natural selection, the offspring tend toward a common body form (morphology). They generally resemble German Shepherds in build, but are smaller, about the size of a coyote. The surviving packs eventually resemble primitive dogs (also called pariah dogs, because they were unwelcome in most human communities).

Primitive (Pariah) Dogs

While some sources define primitive dogs somewhat disparagingly as half-wild mongrels, a true primitive dog is not a mutt that has been separated from its human companions. The dam and puppies found in an abandoned shack by the Humane Society, for example, are unlikely to be primitive dogs, even if they act "wild." They are usually abandoned dogs reverting to a feral state.

Primitive dogs (also called pye dogs or pi dogs, as well as pariah dogs) descend from dogs that followed human migration throughout the globe, living on the edge of camps. But unlike domestic dogs, they have kept to themselves and bred largely without human intervention.

Across the globe, primitive dogs demonstrate similar morphology and and behaviours.

]The Long-term Primitive Morphotype _ wolfish appearance_ wedge shaped head _ pointed muscle _ almond eyes _ erect ears _ long curved tail

 What Primitive Dogs Tell Us

Modern dog breeds derive from those primitive dogs that became domestic animals and migrated with ancient human companions across continents and oceans.

One possible ancestor of both modern and primitive dogs is the Indian Plains wolf. DNA evidence reveals that both primitive dogs and recognized domestic breeds share their ancestors with the Australian dingo (sometimes classified as C. lupus dingo, but more often classified as a subspecies of domestic dog, C.lupus familiaris_dingo.

While the dingo is considered a wild dog, it has a long history of affiliation with humans and was brought to Australia by human migrants from Indonesia between 3000 and 8000 years ago. The Dingo's cousin, the New Guinea Singing Dog, originally classified as a separate species, Canis hallstromi in 1957, was reclassified in 1969 as subspecies of dingo. The classification of canine species is complex because most canines can interbreed.

Dogs vs. Wolves

According to Susan Crockford's paper, Native Dog Types in North America, presented at the 30th congress of the World Small Animal Veterinary Association 2005 in Mexico City, "Dogs appear to have generated on at least three separate occasions (perhaps more) from geographically distinct ancestral populations of wolf" (ie: three different subspecies).

Crockford adds that "such multiple domestication events from geographically distinct subspecies of wolf could perhaps account for some of the variation we see amongst early prehistoric dogs."

Yet despite the possibility that dogs may have been created from wolves multiple times, early dogs were similar in many ways. "All were robust and well proportioned, but similar in general conformation: in all cases, slight differences in size are virtually all that distinguish dogs for thousands of years regardless of where they lived," says Crockford.

According to Susan Crockford, early dogs also "share several features, including a much shortened facial region, crowded teeth, and smaller overall size compared to Contemporaneous local wolves."

The Dog in the Americas Prior to European Contact

 Crockford notes that DNA analysis supports theories that dogs accompanied human migrants from different parts of Asia over centuries. Each time peoples crossed the Bering Strait, they brought their dogs with them. Both dogs and their human companions spread through ancient North and South America.

The peoples of the America's created diverse breeds dogs throughout the hemisphere to meet their needs for hunting, transportation, religious ceremony, and companionship.

An interesting example is the North Coast Wool Dog. Bred by First Nations (Aboriginal peoples) of British Columbia, Canada, and Northern Washington State, USA, the dog was prized for a remarkable coat of thick wool which the people harvested and wove into ceremonial blankets.

The First Nations went to considerable lengths to keep Northwest Coast Wool Dog strains pure. For example, when they could not guard them, they left them on islands with buried caches of food. They limited the reproduction of their less-valued primitive dogs.

The First Nations of southern Vancouver Island, the Gulf Islands, and lower Fraser River in British Columbia, Canada; and Puget Sound and the Olympic Peninsula in Washington State, USA) also kept common village dogs, as did most other Aboriginal peoples on the continent.

 These dogs resembled the semi-wild primitive dogs still found in Asia, Europe, Africa, and Australia. Common village dogs closely resemble a modern day breed: the Carolina Dog.

The Carolina Dog

The Carolina dog in the southern United States may descend from primitive or village dogs kept by Native American tribes or from European dogs who, after decades of isolation from humans, other domestic dogs, and coyotes (with which dogs can interbreed), simply reverted to their wild roots.

 The Carolina Dog's recognition as a distinct type of dog is the result of the observation of a researcher who had done prior work with the Australian Dingo. Lehr Brisbin, Jr. of the University of Georgia, an expert in the study of primitive dogs, began working with semi-wild dogs he found in the lowlands of South Carolina after noting their similarity to Australian dingoes.

 The Carolina dog's ginger coat is also seen in dingoes and other primitive dogs, such as the Chindo-Kae of Korea. They hunt in pack formation, using techniques not commonly seen in domestic dogs. But, unlike primitive dogs, which revert to an annual breeding pattern, the Carolina dog still breeds as many as three times a year.

DNA analysis of Carolina dogs places them at the base of the canine tree with other primitive dogs. This helps us understand the similarity between Carolina Dogs and Australian Dingoes It is no wonder that the Carolina dog breeders like to call their breed "American Dingoes."

Design For Dogs

The relationship between dingoes, other primitive dogs, and modern breeds intrigues dog lovers and scientists alike. While the effects of the dog's relationship with humans has impacted both dog behaviour and human society in ways they we still don't fully understand, we do know this:

The strong family resemblance between primitive and semi-feral dogs across the globe is best explained by Darwin's theory of natural selection. Natural selection is not really a force; it is simply the fact that only certain clusters of traits enable a dog to survive in the wild.

The survival of the dogs that display that narrow band of traits (together with the early deaths of those that do not) ensures that the traits are eventually displayed in most offspring.

That is why wild dogs tend to look alike across the globe, regardless of their origin, and why dogs that go wild revert, after a number of generations, to that common type.

The surviving dogs usually continue to carry all the potential traits that can produce a Pomeranian. But artificial selection, a form of intelligent design, is required to recover those traits, by segregating the dog from the unchecked forces of nature.

Link of Interest:

New Guinea Singing Dog

Dingo and Other Primitive Dogs (Working Dog Web)

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 Note: See also Prehistoric humans: Is Rover's Ancestry the Stuff of Fairy Tales?

Have you heard the story that every domestic dog on the planet is the offspring of grey wolves who found themselves welcomed by warm fires and affection into a human encampment?

Science and Fairy Tales

The idea that wolf cubs and human children became playmates after their parents begin sharing food around a campfire is so widely believed that Bryan Sykes, professor of genetics at the Weatherall Institute of Molecular Medicine at Oxford University and editor of The Human Inheritance: Genes, Language and Evolution, speculates about it in his book, The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry. (Sykes 2001:258-9)

Sykes even suggests that wolves liked humans so much that they put up their cubs for adoption by their new human friends. Wolves who preferred humans to their own species eventually become our domestic dogs.

A charming tale, to be sure, but the path to the dog's domestication is much more complicated.

Multiple Paths To Domestication

In 1997 Charles Vili and his colleagues concluded that dogs split off from wolves more than 100,000 years ago. Their paper Multiple and Ancient Origins of the Domestic Dog, published in Science vol. 276, 13 June 1997, supports wolf ancestry for all dogs from multiple crossings:

The archaeological record cannot resolve whether domestic dogs originated from a single wolf population or arose from multiple populations at different times. However, circumstantial evidence suggests that dogs may have diverse origins. During most of the late Pleistocene, humans and wolves coexisted over a wide geographic area, providing ample opportunity for independent domestication events and continued genetic exchange between wolves and dogs. The extreme phenotypic diversity of dogs, even during the early stages of domestication also suggests a varied genetic heritage. Consequently, the genetic diversity of dogs may have been enriched by multiple founding events, possibly followed by occasional interbreeding with wild wolf populations. Science, vol 276, 13 June 1997

But in 2002, research by Peter Savolainen suggested a "common origin from a single gene pool for all dog populations" between 40,000 and 15,000 years ago in East Asia. In Genetic Evidence for an East Asian Origin of Domestic Dogs

According to the 2002 paper:

The origin of the domestic dog from wolves has been established, but the number of founding events, as well as where and when these occurred, is not known. To address these questions, we examined the mitochondrial DNA (mtDNA) sequence variation among 654 domestic dogs representing all major dog populations worldwide. Although our data indicate several maternal origins from wolf, >95% of all sequences belonged to three phylogenetic groups universally represented at similar frequencies, suggesting a common origin from a single gene pool for all dog populations. A larger genetic variation in East Asia than in other regions and the pattern of phylogeographic variation suggest an East Asian origin for the domestic dog, ~15,000 years ago.

There had also been a theory that the modern dog is a descendant of the East African wild dog known as a jackal. This study points instead to a population of grey wolves in modern India as the ancestor of modern dogs.

Verginelli et al. (2005) put both results under the microscope for another reason. He says the dates used need to be reevaluated because poorly calibrated "molecular clocks" have systematically overestimated the age of geologically recent events. (Note: See our Design of Life article "Molecular clock keeps good time - twice a day?" for a discussion of the problems with using "molecular clocks" to try to reconstruct the history of life.)

Did Dogs Domesticate Themselves?

While the DNA research is open to debate, dogs are clearly the first domestic animals to appear in the archaeological record. Archeologists have found evidence of fully domesticated dogs living with humans in Eurasia at least 14,000 years ago. Despite the fact that dogs require a lot of food and care, says UCLA biology professor Robert K. Wayne,

They must have served an important function in ancient societies, and have been thoroughly domesticated to move great distances without wandering off into the countryside. We believe they were a fundamental part of ancient societies. Dogs may have been valued for their hunting skills, security, transport, warmth, perhaps even helping early travelers to move great distances.

Also, because dogs eat meat, they were sharing with humans a food source that was difficult and dangerous to get - unlike, say, goats. So they were an interesting choice for early domestication. (Humans could, of course, eat the dogs in an emergency.)

Susan Crockford Ph.d., a zoologist, specializes in the domestication of dogs. Crockford, believes thyroid hormones played a role in domestication of the dog. In her paper, Crockford  says "dogs appear to have been generated on at least three separate occasions (perhaps more) from geographically distinct ancestral populations of wolf (i.e., different subspecies)."

It turns out humans may not even have domesticated the dog, in the sense that we usually suppose.

Crockford observes, "Scientists understand very little about the precise biological and anthropogenic mechanisms responsible for transforming wild animals into domestic ones."

She adds that much of what we "know" about breed development is based on assumptions about the early dog/human relationship that are probably incorrect. "There is no evidence to suggest that deliberate human actions precipitated domestication in most animals and the present consensus of opinion is that domestication was initiated by the animals themselves," says Crockford.

We do not really know much about how wild animals usually become tame. Most tame animals were born to tame parents and handled by humans from such an early age that they simply accept humans as safe and friendly.

So what happens when you hand raise wild wolf cubs as if they were puppies?

 In fact, Vilmos Csanyi at Lorend Etvos University in Hungary, together with graduate students, did just that recently. Their work, filmed by a colleague, pointed up just how different the dog is from the wolf in its social behaviour around humans:

At five weeks of age, the wolf cubs were introduced to a room containing their hand-raiser and an adult dog, both sitt