The Essentials: The Dawn of Dogs - Artificial & Natural Selection

Announcement:  I'm adding another topic to the list of typical evolution topics. New topic: What is survival and who are the fittest?

There are a lot of different types of dogs. Big dogs, little dogs, smart dogs, dumb dogs. Pretty much any characteristic you want in a dog you can get, as long as it already existed in a wolf.  All domestic dogs share a common ancestor with wolves. The story of early dog domestication from wild wolf relatives is pretty interesting and has close similarities to the natural selection process that drives evolution.  Before getting into the dawn of the domesticated dog age, a review of modern breeding basics will prove helpful. 

The methods for creating, and refining dog breeds are pretty straight forward. If you to want to breed a certain shape, size, or characteristic into a dog you simply faithfully select for that trait from generation to generation and allow that trait to accumulate more and more in the individuals of subsequent generations.  As an example, let's say you want to develop a really fast dog.  To get thing going quickly you could start by finding a pair of relatively fast dogs then mate them.  However, while pre-selecting for speed in the founding generation will surely help in your doggie development duties, it isn't necessary. To end up with faster and faster dogs you just have to choose the fastest dogs in each generation and continue to pair them with other fast dogs.  Following this simple method will result in faster dogs.  (Real breeders, those who are careful, keep detailed records of lineage in order to prevent family lines from crossing their own paths.  Aside from the cringe factor, inbreeding has some serious and negative genetic consequences that are worth the effort to avoid.)

Variety truly is the spice of life

Artificially selecting for particular traits has produced an incredibly wide variety of dogs but the key to the possibility of selective breeding is that there is inherent variety in every population of dogs.  Every litter will have slow, average, and fast dogs.  This universal variability is true for any population and isn't limited to speed.   Every trait imaginable is variable and is therefore selectable. This is one of the basic, yet revolutionary ideas Darwin described as he laid out his case for evolution.  Variability occurs naturally in populations and variability provides the raw materials for breeders, and nature, to select from.

Variability is what allowed dogs to be domesticated in the first place.  As I mentioned above all domestic dogs are descended from wolves. So what crazy breeder mated wolves and selected the ones most willing to wear sweaters and chase after tennis balls?  The easy answer is there was no breeder.*  The more tricky answer is that the wolves actually selected themselves for domestication.   

This may seem like a crazy idea but it is true and it all connects back to variability in populations.  Just as there are fast and slow dogs there are also skittish and trusting individuals in wolf populations.  Skittishness is a survival mechanism for wolves because it keeps them away from danger.   Trusting behavior has the potential to be very harmful.  Imagine throwing caution to the wind when approaching a dangerous animal. In many natural environments the possibility for being killed goes way up if you are too trusting.   However the natural environment is always changing and what was once an undesirable trait can actually become useful if the situation is right.  

In the case of wolf domestication the major environmental change that happened was the introduction of humans.  In the presence of humans a more trusting wolf will have a new food source open up in the form of human refuse.  To a skittish wolf the garbage pile just outside a human encampment would put them too close for comfort but to the trusting wolf the garbage is just in reach.  This extra source of nourishment increases the trusting wolf’s chance of survival and it will therefore be more likely to produce offspring.  Just like the dog artificially selected for speed by the breeder, the trusting wolf will be naturally selected by its increased ability to survive in the presence of this new food source.  As generations pass, the trusting trait will accumulate in the population and due to variability more and more trusting individuals will result. 

Of course the timid wolves haven't gone extinct because the trusting wolves have moved toward domestication.  As described above there are certainly advantages to being timid and the natural environment of the wolves will continue to provide selection pressures to increase their fitness for survival in that environment too.  

Final note: Wolves can't decide to be timid or trusting any more than I could decide to be 6'11 or have blue eyes. In artificial selection a thoughtful breeder chooses traits to survive from generation to generation.  These traits are available for selection because every population has variety.  Natural selection doesn't have a thoughtful breeder but rather uses survival as its selecting agent.  Traits survive on their own (naturally, if you will) if they help an individual survive and ultimately produce offspring.

* The easy answer is there is no spoon, oops Matrix flashback.  This sentence was originally in the essay but a very dedicated focus group was pretty sour on its inclusion so I promptly removed it.