......The Domestic Dog.....
An Investigation of its Predecessors.


By Alissa Steinke

per kind permission A Steinke 2002

INTRODUCTION

For many years humans and canids have been living in association.This association has been documented throughout history all around the world.The species of CanidCanis Familiaris is formed as a result of human interferance and selection.Although it is well documented that human domestication led to the emergence of Canis Familiaris, the closest ancestor of the species is hotly debated throughout the literature pertaining to evolution and genetics.Two factors affecting the assignment of a direct ancestor include the abundant high variation within the species and the unnatural process of domestication associated with Canis Familiaris. The following report will discuss the hypotheses in evolutionary literature regarding the primary ancestor of the domestic dog.As well as this,variation within the species and its association with domestication will be outlined and directly related to the difficulty in determining the primary predecessor of the domestic dog.

The Process of Domestication and its evolutionary Relevance to the Domestic Dog>

Documented throughout history is the association between canids and humans.Examples of this association begin with findings of early hominids and wolf - like animals in close proximity,dated as early as the middle Pleistocene period.More recent discoveries include remains of a puppy and human buried together in Isreal found to be twelve thousand years old.The close contact of canids and humans over time inevitably lead to the domestication of canids.This ultimately began when caninds were introduced into human communities as an abject of ownership.

Domestication is a process involving two interwoven components - one culturally specific and the other biological.Darwin {1868} decribed domestic animals as an example of unnatural selection analogous to natural selection.This biological component is likened to natural selection,for like natural selection individuals are reproductively isolated in small chorts or demes.Gene flow does not,or rarely.occurs between individuals in the domestic metapopulation and individuals in wild populations.This situation ,over time,is analogous to allopatric speciation,the only accepted form for which new species are generated .The cultural aspect of domestication involves the artificial selection by humans for particular characteristics and behaviours.It is well documented that variables,like coat colour,are associated with temperment traits in many species of domestic animals.Undoubedly docility,tolerance of stress and lack of fear are temperament related characteristics that would have been selected for early in the domestic process.The selected traits are directly opposite to those that enable the survival of wild canids.To be highly perceptible and attain the ability to react to stress quickly promotes a better chance for survival in the wild.Qualities of the domstic dog were affected by natural selection and human artificial selection.Such selection resulted in variable coat colour,carriage of ears and tail,overall size and proportion of limbs - characteristic of the domestic dogs of today.

Domestication is an unnatural process.This is the reason that the domsetic dogs association with domestication makes it difficult to determine its closest ancestor.Human selection is a mechanism unlike any in the wild.Individuals were not selected to enhance their survival but alternately selected to suit the needs of human communities.The extent of intervention by humans throughout the speciation event of the domestic dog makes it difficult not only to determine its ancestor but also when trying to establish the number of founder populations.Domestication was the process by which the variation seen today in the domestic dog was generated.

Variation Within The Species - Canis Familiaris

Domestic dogs live in every part of the human -inhabited world and how great variation not only due to environment factors or distribution in space but variation also attributed to humars artifical selection.The coat colour,size,shape,weight and temperament of a domestic dog can differ dramically.Indicative of this are the statistics given by National Geographic Society {1981} that specify a range of measurements of the domestic dog.These meausurements are given as ;

Head and Body length is 360 to 1450 mm

Tail Length ; 130 - 510 mm

Shoulder Height ;150 - 840mm

Weight ; 1 - 79 kg

A measure of the diversification of variation within the species Canis Familiaris is the recognition of subgroups known as "breeds".A breed is recognized as a relatively homogenous group of animals within a species,developed and maintained by man.Nowak and Paradiso [1983] state there are approximately four hundred breeds of domestic dog of which the American Kennel Club recognizes one hundred and fifty.An example of the variation within Canis Familiaris are the comparisions that can be made between the smallest breed of domestic dog,The Chihuahua and the largest breed of domestic dog,The Irish Wolfhound.The height of the Irish Wolfhound is approximately four times greater than that of the Chihuanhua and the weight thirty times heavier.

The prominent reason that the direct ancestor of Canis Familiaris is unknown is the above - described variation.Such variation in function,form and behaviour makes it difficult for remains and fossils to be interpreted using morphological and physiological methods.The advent of molecular genetic technologies has increased the number of available techniques used to investigate evolutionary lineages at a molecular level.These techniques combat the problem of variant and diverse forms.However,research pertaining to the domestic dogs evolution has not been investigated particularly thoroughly as yet.Until further molecular research is undertaken numerous theories and hypothesis regarding the evolution of the domestic dog cannot be disproved.

Who is the Direct Ancestor of The Domestic Dog?

The origin of the domestic dog is somewhat unknown .Various hypotheses are given through evolutionary literature.Labelling the ancestor of the domestic dog is difficult not only due to the variation within the species and the unnatural associated domestication,but also the unusual interfamily breeding ability species within the family Canidae attain.The species of Canidae that can interbreed include the jackal,wolf,dingo and coyote,all of which are associated with different theories relating to the evolution of the domestic dog.

The phenotypically diverse nature of the domestic dog led Charles Darwin {1868} to believe that the species had originated from more than one wild population and from more than one species of wild canid.Along the same notion were the hypotheses of Austrian Behaviouist Konrod Lorenz.Lorenz suggested that the behaviour of domestic dogs could be associated and compared with the behaviour of both the wolf and the jackal.These suggestions have since been reviewed and to a certain point rejected.The advent of molecular technologies has ascertained that the jackal is distantly related to the domestic dog.

Interestingly a concensus is emerging throughout literature with the introduction of mor molecular papers.More researchers are implying that the wolf was in fact the predecessor of the domestic dog.In particular ,two research papers investigate and compare the mitochondrial DNA of domestic dogs,wolves,jackals and coyotes.Results conclude that variation exists in all sequences,interspecies included.Variation within the domestic dog was significant however breed could not be determined..From the results deviations of mitochondrial DNA sequence were least between the domestic dog with the jackal and the coyote.Therefore conclusions were made that the domestic dog arose from founding wolf populations.

Although conclusions were made from the molecular papers that the wolf is the closest relative of the domestic dog -limitations regarding this research are numerous.Mitochondrial DNA was used to examine the relationship between the canids.However mitochondrial DNA is passed on from the mother to the next generation therefore this molecular analyses would not have found the effects of siring by coyotes or jackals.As well as this,the dingo was not included in any of the studies.Although it is thought the dingo originated from the domestic dog,the dingos closest ancestor and its relationship with other canids is strongly debated.One author debates that all domestic dogs in fact originated from the dingo,not the other way around.Another ,fault of the molecular papers is the fact that the grey wolf and red wolf are the only types of wolves used in the analyses.Clutton Brook[1984] suggest that the closest ancestor of the domestic dog is neither the red wolf or the grey wolf but in fact the Indian wolf.Where as Olsen[1977]believe the domestic dogs originated from the Indian Wolf and Mathews[1971] stated that various races of wolves are the progenitors of the domestic dog.

As has been detailed,numerous hypotheses have been given explaining the origin of the domestic dog.molecular evidence suggest that the greay wolf and the red wolf ar the closest relative of the domestic dog.However such studies are deficient regarding the number of canids analysed.Behaviouists suggest domestic dogs could have derived from jackals and some biologists suggest coyotes.As well as this,another author states that the breeds of domestic dog originated from the dingo.This example of disagreement is rife throughout the literature.

Overall the phenotypic variation evident in the species Canis Familiaris makes it difficult to behaviourally or morphologically determine the origin of the domestic dog.Therefore molecular research is the most reliable technique in determining the predecessor.However,thorough molecular studies are presently unavailable.Further molecular research will undoubtedly determine the most recent ancestorof the domestic dog.However until such research is undertaken it is unwise to eliminate any species of canid.Although molecular technology will determine closest relative of Canis Familiaris ,it is unlikely that the exact time and place of speciation will be confirmed.Questions that may never be answered include;

1]Did the Domestic dog arise from one founding event or many ?

2]Has the occurrence of hybridization between domestic dogs and wild canids after the speciation event,contributed to the vast phenotypic variation evident in the domestic dog ?

By Alissa Steinke 2001

References;

Corbett,L[1996] Dingos;Expatriate wolves or native dogs.Nature Australia,25,45-55

Clutton-Brook J [1984] Dog-In Evolution of Domesticated Animals

Darwin C [1868] The variation of Animals and plants under domestication,vol 1

Nowak RM & Paradiso [1983] Walkers mammals of the world

Olsen SJ The Chinese Wolf ancestor of New World Dogs Science .197,553-555

Serpell JA the domestic dog ,its evolution,behavior and interactions with people

Wayne R K & Ostrander;Origin[1999],genetic diversity and genome structure of the domestic dog.

Wayne RK [1993] Molecular evolution of the dog family -Trends in genetics,9,218-224

Back to Articles

Back to Home Page