the evolusion of brachychephalic Molossoids dogs
Observations that differences, and often considerable ones, exist between different kinds of dog must have been made since the time man and dogs began to live together, and began to be recorded by man even in the earliest days of writing and pictorial representation.
The first written account of different canine species was done by Xenophon, while the first description of the abilities and morphological features of individual species was made by Aristotle, who placed them in different categories. One of these was BRACHYCEPHALIC (shortfaced) DOGS (see the section entitled ‘The Odyssey of the Word “Molossus”).
These days these animals are known as ‘Molossoid’ dogs, ‘Mastiff-like’ dogs or Dogues.and I think anyone who owns an animal like this will have realised just how different it is in character and temperament. Its distinctness lies mainly in its NON-GREGARIOUS behaviour, i.e. its difficulty in living together with other dogs, other members of its own breed, or humans. In other words, they are SOLITARY animals, like their relation the BEAR. This fact can be explained by various morphological features that are connected with their origins and evolution.
In order for this to be understood, a few principles of evolution need to be outlined first:
1) Three basic patterns
Two or more groups from the same
stock evolve differently, usually because
they become isolated geographically
from one another and develop in
response to differing environmental pressures.
Genetically related groups become
isolated but evolve in similar ways,
in response to similar selective pressures.
Completely unrelated animals evolve
similar structures in response to
similar environmental pressures.
2) In nature there is a physical quantity that does not suffer the negative effects of reproduction and this is TIME. The distinctive characteristics of brachycephalic dogs in terms of the head, jaws, teeth and paws, are: A) ( the head) a relatively broad skull with a short face in relation to the brain cavity, which in certain breeds (e.g. the Bulldog) assumes extreme dimensions and creates a particularly pronounced stop. This causes prognathism (protrusion) of the lower jaw, while the molars and premolars of the upper jaw are curved. As has been demonstrated by Huber and Lueps, in the area of the face, a short skull affects the width of the head, the width of the muzzle and the distance between the eye
Β) (the jaws and teeth)
The canines are sharp, long and straight or very slightly curved. The premolars have a cutting action. Particularly the 1th molar (red), which has a scissor-like action like the incisors (front teeth). The molars are relatively flattened.
The canines are short and curved. The 1th molar(red) functions both as a cutting tooth and as a grinding surface. Usually the first premolar is absent. The molars have large surfaces for grinding food. The lower jaw is curved like a giant spoon. It bears an amazing resemblance to the jaw of a bear-dog and bear.
Usually the first or the second premolar is absent. The 1th molar(red) functions as grinding surface. The molars relatively large grinding surface(omnivorous)
Be ars an amazing resemblance to the jaw of abrachycephalicdog and bear dog
The early carnivores developed special teeth called carnassials. The last premolar in the upper jaw and the first molar in the lower jaw (red)were modified to act like scissors, shearing meat into easilly swallowed chunks.
C) ( the soles)
We have, therefore, an animal that possesses some of the biological features of bears and wolves. In order to understand how these features are used, it is necessary to study the different hunting techniques of the bear, the wolf or the African wild dog (Lycaon Pictus) as they have been portrayed in pictures or shown in TV documentaries.
The wolf usually hunts plant-eating animals that are bigger and heavier than itself and for long distances, running on its toes (i.e. digitigrade), and together with other members of its own species, i.e. as a pack. During the course of the hunt, which develops while the animal is on the move, the wolf inflicts a wound on its victim with its canines, particularly on the thigh or in the armpit, which contain arteries through which flows 70% and 30%, respectively, of a mammal’s blood. Therefore, a short curved canine would not be able to inflict a deep wound and might even get stuck in the wound, or at worst be uprooted, since the whole process takes place while the animal is in motion. Therefore, wolves’ canines are long, sharp and relatively straight so that they can be pulled out easily. Also, they have scissor teeth so that they can cut up their victims’ flesh in a rapid succession of bites and devour it almost whole, without grinding it, since they face competition from many other predators.
Bears, on the other hand, hunt alone, preferring smaller and lighter prey. They chase their prey over very small distances but with explosive turns of speed and so their soles are designed to serve this purpose (semi-plantigrade/plantigrade). When they catch their prey they immobilise it by lying down on top of it and blocking off the breathing tubes with their pincer-like incisors. Once its victim is dead, a bear will feed relatively slowly as it does not share its kill with any other competitors and can cut off large chunks of meat containing bones, and this is why it has short, broad, curved canines and a spoon-like lower jaw. The whole system creates a huge momentum which (through the molars) grinds up the food – a particularly useful attribute as bears are omnivorous animals.
These features of bears, therefore, are also to be found in brachycephalicdogs, which display a similar form of behaviour. The St. Bernard dog, for example, does not lie down on top of frozen travellers in order to warm them up – as we believe it was born to do – but because it is merely instinctively expressing a latent genetic predisposition it has inherited from the bear-dog. The English Mastiff does not excel as a shepherd dog because by nature it is a solitary animal. Likewise, the increased length of the carpus and tarsus(weak pasterns) usually displayed by giant brachycephalicbreeds is not due to rapid growth but to a hereditary predisposition that they have acquired from their plantigrade ancestor. It is a bit like the hunting dog that gives the dead quarry to a human instead of consuming it himself. Finally, the references that can be found in the standards of these breeds to the possible absence of the first premolar and prognathism are not accidental but are based on actual observation. Personally, then, I believe that the brachycephalicdog is ONE branch of the divergent evolution of the bear-dog (the OTHER branch is the ancestor of the modern bear). It is a dog that exists in a variety of different sizes (e.g. the St. Bernard, the Bulldog and the Boxer), just as the bear exists in a variety of different sizes (e.g the sun bear and the spectacled bear, which are dog-sized,dog-teeth animals). It is a dog that is native to both Europe and Asia and the different sizes it takes can be explained by looking at the distribution map of the brown bear. The map shows us that in the Mesopotamian region (Iraq-Iran) no giant species of bear exists and, in fact, I would say that in the whole of South-East Asia only small species of bear exist, together with the plant-eating panda. Therefore, the role of the superhunter is to be found in the other branch, i.e. the ancestor of the brachycephalic dog, while the opposite is true in Europe, where the bear is the dominant species and so the brachycephalicdog has been reduced to playing a different role, with the result that its body is smaller (a case of parallel evolution). Shortfaced dogs have come down to us mainly in the form of shepherd dogs, for reasons that are explained in the articles ‘The Odyssey of the Word “Molossus”’ and ‘The animal’s relationship with humans’. The cause of this development, which began about 3,000 years ago, was man’s attempt to create a type of dog that would combine the physical strength of a short-faced dog with the ability to cooperate (an ability that short-faced dogs lacked) with the other members of a group guarding a flock, which had to face packs of wolves .
Of course, it could be claimed that this is a classic case of convergent evolution, in which animals sharing the same environment have developed a similar morphology, as in the case of dolphins and sharks. The reply to such a view is that: a) although the dolphin (a mammal) lives in the sea, it uses lungs to breathe;
b) the skull, jaws and front fins of the dolphin are totally different to those of the shark (a fish), which is an important factor as these features change only very slightly in the course of evolution (besides, in the evolution of the human species it is also the skull, teeth and soles that are evaluated, as in the case of Lucy).
It could also be claimed that all dogs are descended only from the wolf, since we have DNA tests to prove it. My answer to this would be that the tests we have are only fragmentary and we should be extra cautious in this matter since the data under investigation comes from an administrative and not a biological approach, from people who define dogs like the English Mastiff, the Mastino Napolitano, Boxer and Bulldog only by using phrases like ‘nice colouring’ or ‘majestic movement’ or ‘the kind of dog that I like’.
Finally, because we interpret the origins of brachycephalicdogs mainly through historical data that is very often based on myth and fiction and not on real events, we should seriously take into consideration only data that can be verified by history and biology.
I hope that this study will help to enhance understanding of a dog that was living on earth millions of years before humans were and whose uniqueness lies not in the fact that it was the dog of Alexander the Great or Bismarck or Tsar Alexander but that it is a species in its own right, just as man is.
Xenophon -- Aristotle -- skull -- jaw of a bear-dog
View of underside. Side view of underside -- African wild dog -- wolf -- Bears
weak pasterns-- plantigrade ancestor -- ancestor of the modern bear -- sun bear -- spectacled bear -- the ancestor of the brachycephalic dog -- DNA tests
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