The process of domestication of dogs, which has been extended for several centuries, continues to generate many curiosities. One of them is, without a doubt, the reason why there are dogs with drooping ears and others that retain the erect ears of their wolf ancestors.
To analyze this curiosity, next, we will see the evolutionary aspect and the human influence that can explain these aesthetic differences.
Darwin’s questions about dogs with drooping ears
For many centuries, researchers have believed that drooping ears were, more than anything, a characteristic of individual races. Consequently, the main factor for the perpetuation of this trait in particular dogs, and not in others, was usually attributed to human intervention during the process of standardization of dog breeds.
However, some recent studies have once again pointed to an ancient theory proposed by Charles Darwin. The famous British naturalist used to associate the existence of dogs with drooping ears to the domestication process.
This hypothesis, belonging to his extensive bibliography on the evolutionary process of species, has not received much attention since the 19th century. However, this could change now that many scientists seem to support what they call domestication syndrome in dogs.
What is domestication syndrome in dogs?
To answer this question, we need to talk a little about dog domestication. First of all, it is necessary to understand that it is a long process that could have started about 20,000 years ago.
Throughout these centuries, dogs have experienced numerous physiological, aesthetic, genetic, and behavioral changes to their wolf ancestors. Precisely, these changes are what have allowed them to differentiate to the point of generating a new species within the family of canids.
One of the great mysteries about domestic dogs is to understand how they began to be: the meek wolves have approached human villages in search of warmth and shelter. Then, the men realized that the presence of these wolves could be very beneficial for both parties.
Years later, men also perceived that, through selective crossings, they could obtain, highlight, or control certain aesthetic and mechanical features in dogs.
With these actions, optimal specimens were obtained for hunting, grazing, or directly individuals that met the aesthetic patterns appreciated in their time and society.
What is the relationship between dogs with drooping ears and domestication syndrome?
As Darwin seemed to suppose there by the nineteenth century, the domestication process has had an impact on both the appearance and behavior of dogs. Currently, we talk about the domestication syndrome, which includes the various changes observed in the morphology of an animal that is related to the domestication process.
In dogs, these morphological alterations become quite evident when compared to wolves. Some examples are the jaw and the smallest teeth, the spots or changes in the pigmentation of the fur, and the drooping ears.
According to experts, dogs with droopy ears have a slight deficiency of cells derived from the neuronal crest. As a consequence of this deficit, embryonic stem cells cannot perform optimally at the time of forming the cartilaginous tissue of the ears, which causes them to ‘fall off’ and not be erect.
This deficiency would not be accidental but would result from human intervention at the crossings to create and standardize the different dog breeds. From the beginning of the domestication process, human beings tended to choose the calmest and most sociable specimens.
Neural crest cells and adrenaline
Possibly, one of the reasons why there were less aggressive wolves than others was precisely a lower concentration of neural crest cells.
In addition to generating some morphological changes, such as drooping ears, this lower production of neural crest cells also reduces adrenaline secretion, which makes individuals more docile and less reactive to contact with humans.
By selecting and crossing the most social wolves, several generations with deficiencies of neural crest cells have been born, which has allowed obtaining specimens with increasingly friendly behavior and less similar to wild canids.