Jul 13 2021

Dogs Understand Humans

Published by under Evolution
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Regardless of whether or not you are a cat person or a dog person (I have both as pets, as well as a reptile, and have had birds and fish), there is no denying that dogs are excellent human companions. No other animal known is capable of the same relationship with people. Researchers have been trying to understand the origin of this special relationship, with some interesting results.

First let me review the results of a new study, and then add in some background. The question the researchers are trying to address is this – how much of dog behavior is shared with their wolf ancestors? Specifically, dogs and wolves share a common ancestor between 12,000 and 40,000 years ago. There was likely a lot of interbreeding during this time (as there still is) so it’s probably not possible to declare a clean break. But they are now distinct subpopulations. Dogs show an incredible ability to understand their human companions, even without extensive training. The question is – how much of this ability is innate vs trained and how much is shared with wolves?

The study compared 44 dog pups with 37 wolf pups right after birth. The wolf pups were raised by humans, with maximal human contact after just a few days from birth. The dog pups were kept with their litters with minimal human contact. They were assessed at 5-18 weeks old. The authors found that the dog pups were able to follow human direction (such as pointing and other cues) toward a food reward. The wolf pups did no better than chance, indicating no benefit from the human cues. Dog pups were also able to respond to novel cues, like playing a block next to the target bowl. Further, when a stranger was introduced the dog pups came up and interacted with them (wagging their tail and licking their face) while the wolf pups when into a corner and hid.

None of this is surprising, and it is all consistent with prior research. But it does help confirm that these stark differences are innate, and not learned. So what’s going on?

Initially it was assumed that humans domesticated dogs from wolves, taking them into their community and then selecting them for doggy traits over thousands of years. However, based on fossil and other evidence, the current prevailing theory is that wolves likely were living on the edge of human habitats. Humans are a potential source of food, and perhaps even protection from even larger predators. So hanging out on the fringe could have been a successful survival strategy.

However, this strategy is also contingent on the humans not being too afraid of you, or they will kill you or chase you away. So these proto-dogs were selected for and evolved the ability to seem less aggressive and more friendly to the humans, to be less shy and fearful of them, and to read humans so they could tell if they were friendly or threatening. This could have been the foothold into the evolving relationship.

Therefore, it’s possible that protodogs were already highly evolved for human compatibility before humans went from tolerating them on the fringe of their living space to welcoming them into their living space. Once that transition happened, then the evolution of dogs would have progressed rapidly. It’s also possible that this was a two-way evolution, each species adapting to some extent to the other. The result was a symbiotic relationship. Dogs now had a far more reliable source of food and protection. In return they provided companionship and protection to their human symbionts. Meanwhile, human tribes who learned to form relationships with dogs would have had a huge advantage over those that didn’t. Dogs were well worth the cost of some food scraps. In the third phase of dog evolution they were deliberately bred to have features optimized for specific jobs, like hunting or herding.

The end result of this process is that modern dogs have a very high neuronal density with an incredible ability to interpret the emotions and desires of their human companions. The authors of the current study go as far as to say that dogs likely have a theory of mind, the ability to think about what another creature is thinking. Dogs can follow a pointing finger. This may not seem like much, but this is a rare ability among animals. Dogs even do it better than chimpanzees.

Thousands of years of evolution have made dogs and humans partners. In many ways I think we are lucky to have benefited from this happenstance of evolution.

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