Category Archives: The Origin of Dogs

12/30/12

Razboinichya Rover

ResearchBlogging.orgIn 1975, a well preserved “dog-like” skull was found in the Razboinichya Cave (in the Altai Mountains in Siberia).  Because this skull was so well preserved, it provided opportunities for study between this animal, dogs, and wolves.

A wolf skull, dissimilar to the skull found in Siberia.

This cave was a home to many other archeological finds. There were bones from numerous other mammals, from reptiles, amphibians, and fish.  About 71, 290 mammalian bones and fragments were uncovered and removed from this site. The “dog like” skull was found among the bones of foxes, cave hyenas, and gray wolves.

But what exactly was this skull?

After extensive analysis, the pooch in the cave was found to be most similar to fully domesticated dogs from Greenland that existed 1000 years ago.  The Razboinichya Rover was unlike wolves, both modern and ancient.

They look at the skull shape, the arrangement of the teeth, and so forth.  The short and relatively broad snout and the tight teeth, both indicate that this animal is more dog than wolf.  The only slight anonamly is that the teeth of the Razboinichya canid is inconsistent with the Greenland domesticated dog.  In all other measurements, this canid is a dead-ringer. Continue reading →

10/29/11

McGreevy on A Modern Dog’s Life

This post is part of the McGreevy seminar series. Click here for the index.

 

McGreevy spoke about some of the demands dogs face in the current era, and explained that these issues are considered in more detail in his book A Modern Dog’s Life.

Basically, McGreevy asks us to appeal to the types of things dogs have to ‘put up with’ in the modern world.  The difficulties of dogs in the 21st century are far different to those of their ancestors.

Dogs have to deal with physical barriers in the modern era.

We have co-evolved, so in a way, we exploit each other, and dogs do cope quite well considering what we do to them.  For example:

Dogs are expected to get in and out of cars. The car is a noisy machine that suddenly transports dogs to a entirely different destination, in which dogs are then expected to cope with.

Dogs experience man-made boundaries and barriers. There are no doors or fences ‘in the wild’.

Dogs walk on man-made surfaces.

Dogs tolerate us touching them in ways other dogs never would.  We touch dogs around the neck. We stare them in the eyes. We hug them.

 

Clearly, there are hosts of stresses for ‘modern dogs’ that need to be considered in studying dogs.  He appealed for applied ethology – ethology that considers human-dog interactions.

 

This train of thought made me think about the kind of stresses I place on my dogs, without even realising it.  I expect my dogs to tolerate me exiting through a door – barriers like this, and ‘pack members’ leaving like this, is quite unnatural.  (For the most part) they don’t attack brooms, the poop-scoop, or other items, even though they are normally displeased about their presence.  I clip their nails!  I keep a bird in a cage that they have to ignore.  All really unnatural behaviours that our dogs, by miracle of being dogs, have learnt to deal with.

What have your dogs learnt to deal with, that their ancestors surely didn’t?

 

This post is part of the McGreevy seminar series. Click here for the index.

Continue reading →

02/26/11

Belyaev’s Fox Experiment – Index

After frequently finding myself encountering references to Belyaev’s fox experiment in a number of dog-related texts, I felt the need to investigate his experiment more thoroughly.  This has resulted in a lot of reading, but a lot of new found knowledge.  From this reading, I hope to have a better understanding of the connection dog-authors are trying to make between dogs and the fox experiment. I hope it also proves useful for my readers.

Part I – Introduction
A summary of the work of Belaev in his ongoing experiment with foxes.

Part II – Changes
Description of the changes observed in Belyaev’s fox experiment.

Part III – Answers
Possible reasons for the changes seen in the foxes in Belyaev’s experiment.

Part IV – Dogs?
Why does the Belyaev fox experiment matter to dogs?

I hope this series has been of interest, as I thoroughly enjoyed researching.  I did cut out some bits and pieces, so please feel free to comment if you feel I haven’t answered a burning question for you! Additionally, if you would like in text referencing, I can provide such.

References: Continue reading →

02/26/11

Belyaev’s Fox Experiment – Dogs? – Part IV

This post is part of the series on Belyaev’s fox experiments.
(index | part I | part II | part III | part IV )

You may have read my previous three posts, which have explained details of Belyaev’s fox experiment.  And you may have wondered the relevance of studying foxes on a blog about dogs.

Obviously, foxes are not dogs. They’re not even wolves. However, they aren’t far off it.  Regions of fox chromosomes correspond with those of the dog (to be specific, fox chromosome 1 seems to indicate a fusion between chromosomes 1, 33 and 12 as we see today in the dog).  That means that we should not disregard this research because it is a different species.

Chiefly, this study can be used to examine the process of dog domestication. Because domestication and associated variability seemingly occurred relatively quickly, there have been doubts that Darwinian theories are applicable. However, this study shows that significant changes can be seen in a brief period of time and generations. Coppinger (in his book Dogs) uses this study to show how quickly a significant change can take place – in the foxes here, significant morphological and physiological changes were seen in just 8-10 generations. This all occurred with just one selection pressure – selecting for ‘tameness’.

Dogs are very different to wolves.

This is surprising on a surface level, but when considering the causes of these changes it is not so remarkable.  Indeed, these changes have been seem occur in a similar way in terms of wolf’s domestication to dogs.  For example, dogs play as adults while wolves do not, and dogs carry many other juvenile-wolf characteristics.  Furthermore, dog puppies respond to human cues like fox domesticated pups and indeed are ‘dog like’ in many behavioural ways.  It is likely that the causes of the foxes changes are also the reason the wolf is the dog we know today.

On a larger scale, this research shows that we can select for nature.  Consider that these dogs were never trained, but were selected on their genetic amicability to humans.  This is a loud message on how we should be selecting dogs to breed from.

I hope this series has been of interest, as I thoroughly enjoyed researching.  I did cut out some bits and pieces, so please feel free to comment if you feel I haven’t answered a burning question for you! Additionally, if you would like in text referencing, I can provide such.

References: Continue reading →

02/19/11

Belyaev’s Fox Experiment – Answers – Part III

This post is part of the series on Belyaev’s fox experiments.
(index | part I | part II | part III | part IV )

There are several theories that have been put forward regarding the origins of the physical characteristics seen in Belyaev’s foxes.  I will rebut some theories, and consider the plausibility of others. There are no definite answers, just some realistic theories.

Experimenter bias

One of the most popular anecdotal suggestions is that perhaps the experimenters unconsciously selected for more dog-like physical characteristics.  Personally, I think this illustrates a lack-of-faith in the scientific method.  The nature of the tests has been clearly outlined, and we must have confidence that this method was adhered to.  If there were serious doubts, the method allows for replication.  As replication has not occurred (mostly due to expense inhibiting the experiment) we can conclude that the experiment’s results are plausible in its current form. (The empirical world loves nothing more than proving others ‘wrong’ through replication.)

Mutations and Inbreeding

Another loud argument is the notion that the initial stock was carrying mutations or unusual traits, or that these changes were as a result of mutations.  Because of the inbreeding of the experiment, these mutations were amplified. This can be rebutted in a number of ways.

Firstly, the foxes were not inbred.  This fox population was frequently outcrossed to other commercial fox farm stock, and this has meant that the domesticated fox population has an inbreeding coefficient of 0.02 to 0.07.

Secondly, many of the novel traits outlined in part II are in fact not recessive. This means that the foundation population’s mutations would have been apparent on commencement of the experiment. This was not the case – these traits became apparent over the course of the experiment, and not in the beginning stages.

Another idea is that random mutations are the cause of these traits.  However, Belyaev determined that the rate of change in the domesticated strain was “2 or 3 orders higher than the expected frequency of spontaneous mutations”. This means that it probably not mutations that have caused the changes documented.

If we consider the mutation route as plausible, the suggestion with the most worth is Vavilov’s theory of homologous variability.  Vavilov’s theory suggested that similar gene sets can give rise to similar mutations, and so we can apply the term ‘similar gene set’ to all foxes, and mutations to their unique traits. This explains how foxes, despite being unrelated, developed similar traits just by the nature of being a fox with a fox gene set.

However, mutations probably did not have a role in the changes seem in the foxes.  What is more likely is that behaviour and anatomy may be linked in some way.

Depigmentation is a characteristic in dogs that was also seen in domesticated foxes. Photos © Ruthless Photos

Depigmentation is a characteristic in dogs that was also seen in domesticated foxes.Photos © Ruthless Photos

Selecting for many genes

The behaviour of ‘tameness’ is a varied trait, and so is controlled by a number of genes.  Because there are a number of genes involved, this means that selecting for tameness, and so also a number of genes, could have a profound affect.

Selecting for important genes

However, what is a more convincing suggestion is that perhaps this rapid change may have been as a result of selection may have been acting on relatively few genes, and genes that have an important regulatory role.  This would mean that if a ‘master’ gene was being selected for, this could have far reaching implications.  Here we reach the most convincing theory: That selecting for tameness was selecting for a major, complex, hormonal regulatory gene (or genes) which has far ranging implications on the rest of the animal.

The traits in foxes are found in many different domesticated species. Because of these similarities, Belyaev thought that early changes for amenability to domestication must be related to domesticated physiologies.  Because behaviour is regulated by neurotransmitters and hormones, modifying these elements through selecting behaviour would also have affects physiological parts of the animal.  Even though mammals are varied, their physiological processes are quite similar (their hormones, neurotransmitters, etc) – so this would be the basis for many domesticated mammal species showing similar traits.

Domestication/tamability is behaviour that is rooted in physiological changes and systems (e.g. hormones and neurochemicals).  Changing these complex systems would have far-reaching effects on the development of the animals themselves. And as all mammals are controlled by similar bigger-regulatory systems, this is seen as a reasonable explanation for the changes.

Hormone selection

‘Tameness’, ‘nervousness’ and ‘aggression’ is probably controlled by the endocrine system.  As described in the last post, serotonin, corticosteroid, cortisol, and adrenocorticotropic hormone were all found to be reduced in domesticated foxes. These hormones are responsible for behaviour that was selected for.  However, these hormones have a much bigger role in the endocrine system, so selecting for hormones would have had an extensive role and account for many of the changes observed in the domesticated animals.

Indeed, even the colour changes seen can be accounted for by hormones.  Hormones are linked to pigmentogenesis, agouti, and melanin.  The endocratic system can also explain the moulting changes in the domesticated foxes.

The endocrine system can explain many of the changes in the domesticated foxes behaviour, but this system also has a big role in development.  In selecting for genes that control behaviour, selection was also made for genes that control development.

The presence of juvenille traits (e.g play) in adult dogs was also seen in foxes. Photos © Ruthless Photos

Development mechanisms

The characteristics that the foxes adopted are those that are similar to juveniellism.  In this way, the development of the domesticated foxes can be described as ‘retarded’, as even adults have juvenile behaviours.  In this way it is thought that genes responsible for development have in some way been selected for.

These developmental changes start from embryos, with the hormones already described affecting the whole development process.  Even colouration/pigmentation has been linked to melanocyte and melanoblast activity in embryonic stage.  Neucrocrest cell migration would be delayed, which means messages to mature would not get to some body parts.  This would also have implications to the socialisation period, and be responsible for the floppy ears. Changes in the maturation timing have been seen.

Behaviour selected for seems to have been controlled by a few genes, but these genes were also responsible for a high level of regulation (i.e. hormonal level, and influencing development) and hence the foxes had a range of phenotype changes that accompanied the selected behaviours.

This is what domestication looks like

The literature review strongly stated that domesticated foxes, and their characteristics, are not terribly surprising.  Belyaev says that the “data demonstrate for foxes the kind of variability in similar characters and functions that is often observed in the domestication of other species of animals.” Because all domesticated animals have ‘done the same thing’ (in terms of phenotype traits), then this must be an implication of domestication and not an innate genetic quality of the fox population.

It is from these conclusions that the next post will start to make conclusions that relate to the domestication of dogs.  As our dogs display the domestication characteristics of the fox, this experiment is valid to our understanding of the history of dogs.

References: Continue reading →