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Canine evolution
After the mass extinction that put an end to the age of the dinosaurs, new predators emerged to take their place.
One of them was a small tree-dwelling creature called Miacis, the common ancestor of wild canines, foxes, raccoons, and bears.
The canine group has specialized for lowland environments and has developed cooperative hunting techniques that require pack organization.
Fig 1: Miacis representation
Animal domestication is a co-evolutionary process, in which a population responds to selective pressure while adapting to a new niche that includes another species with evolving behaviors. Most evidence suggests that the domestication of wolves took place between 15,000 and 10,000 years ago, before the development of agriculture, making wolves the first domesticated animals, even before chickens, horses, and cows.
The archaeological record and genetic analyses of the first undisputed domestic dog correspond to the Bonn-Oberkassel dog, buried alongside humans more than 14,200 years ago, in Germany. However, prior to this period, a genetic divergence between wild and domestic canines had been occurring around 60,000 – 20,000 years ago, and even the oldest skeletons of what are believed to be dogs are dated to approximately 33,000 years ago. In general, the results show that this process of domestication began in Eurasia, but that it may have occurred simultaneously in different parts of the globe. Thus, there is no firm consensus on the temporal and spatial beginning of the domestication of wolves.
Fig 2 : wolf helping humans hunt
Domestication process:
The beginning of domestication can be explained through 2 main theories:
Pet keeping or cross-species adoption hypothesis – Humans adopted wolf cubs that were more docile;
Commensal scavenger hypothesis – The search for food began to bring wolves closer to the garbage and kitchens of humans, making those with more docile and curious personalities accepted in the human environment
The second theory is the most widely accepted, since the adoption of wolf cubs would certainly pose a serious risk to humans. However, both theories converge in the same direction – wolves no longer needed to work so hard to obtain food and thus lost some of their adaptations, giving rise to the different species of domestic dogs of today.
A very clear example of this loss of characteristics from wolves to dogs is the color of their fur. In dogs, the coat can range from the lightest to the darkest shade, be smooth or even be composed of spots of various colors. This resulted from the lack of need for camouflage in dogs, unlike in wolves.
The dogs' ability to alter their diet to include more starch and less fat—changes linked to a more commensal lifestyle—appears to have been influenced by the artificial selection of these animals, which is another intriguing attribute.
The motivations behind the domestication of wolves are as follows: (1.) more effective hunting and (2.) greater protection of humans from potential predators and/or enemies.
The differences in behavior between dogs and wolves may be contributed by structural variation in genes associated with human Williams-Beuren syndrome, a syndrome that causes increased hypersociability, an essential characteristic for the domestication of wolves.
In 2014, a genetic study among wolves and dogs found that dogs' tameness was not a reduced response to fear and instead proposed that the dogs' learning and memory abilities helped them lower their level of fear towards humans.
There also seems to have been a modification in the biosynthesis of adrenaline and noradrenaline during the domestication process, leading to meekness and an ability to process emotionally.
No species in the world has as much diversity, or has been subject to as much artificial selection, as domestic dogs.
Since the mid-1800s, the practice of dog breeding has exploded, and today 344 breeds are known worldwide, all of which carry about 98% of the DNA of wolves.
Fig 3: Dogs evolution throughout time by Plassais et al.
Nowadays, we can't deny that humans see dogs as an important form of companionship, and a study even found in 2015 that prolonged eye contact between a dog and its owner increases the levels of oxytocin in both, a hormone associated with maternal bonding.
This human-dog bond is not recent, as no other animal species has been so consistently included in human burials (many of them treated and adorned properly) since the arrival of humans on the planet.
Hugo Anselmo
Ecologist biologist
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