The wagging tail of a dog is a wildly acknowledged symbol of joy and excitement in our four-legged friends. However, this behaviour is largely unexplained and misunderstood. A recent opinion piece by Leonetti et al sheds light on this enigmatic behaviour, inviting a deeper investigation into its mechanisms, evolution, and significance.
Tail wagging is a nuanced behaviour that helps dogs communicate a plethora of information to other dogs and humans. Functionally, it is a communication tool, conveying emotions, intentions, and requests; it also has a left or right bias depending on whether the dog is responding to something positive or negative. The association with positive and negative stimuli suggests that this behaviour may be related to hormones and neurological processes.
Studies suggest a stark contrast between dog and wolf pups, hinting at the influence of domestication. According to the opinion piece, the long process of domestication had a number of impacts on dogs, including fur depigmentation, reduced facial skeleton and teeth size, changes in overall body size and proportions, the emergence of physical attributes, reduced brain size, reduced aggression, increased docility, and reduced responses to stress — as well as the development of tail wagging. These evolutionary changes and adaptations have helped dogs to adjust to co-living and cooperating with humans.
The evolutionary trajectory of dog tail wagging presents two compelling hypotheses: the ‘domestication syndrome’ hypothesis and the ‘domesticated rhythmic wagging’ hypothesis. The former suggests that tail wagging may have emerged as a by-product of selection for other traits during domestication, such as docility or tameness. On the other hand, the latter hypothesis suggests that humans may have actively selected for dogs with more frequent and rhythmic tail wagging, driven by an innate preference for rhythmic stimuli. It is not yet known whether either of these hypotheses are correct, or whether there is a more compelling answer out there; however, the authors of this opinion piece suggest that answering this question requires further experiments that better quantify tail wagging and lead to a deeper understanding of how this behaviour is controlled.
Dog tail wagging, often dismissed as a simple gesture of happiness, is a surprisingly complex phenomenon that requires further scientific exploration. By peeling back the layers of this behaviour, the wagging tail of a dog may help us gain a deeper appreciation of the rich tapestry of human-animal interactions and the evolutionary forces that have shaped them.
This article is based on Leonetti S, et al. Biol Lett. 2024; 20(1):20230407.
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