How Will Dogs Reshape Nature Without Humans to Control Them?
As dogs go wild, how will artificial selection give way to natural selection?
Posted Oct 14, 2018
How will dogs reshape and redecorate nature in a world without humans?
In a previous essay called "As Dogs Go Wild in a World Without Us, How Might They Cope?" I wrote about how dogs might adapt to a world in which we no longer control their lives. It will surely be a challenging time for our canine companions, and it seems that their losses would far outweigh their gains even if they are free of the numerous constraints we place on them. However, we need to be very careful about our predictions about what and how dogs will do in a world without us, as there's no straightforward shopping list of traits that would necessarily decrease their survival and those that would favor the ways in which they would adapt. It's also essential to consider how individuals would adapt, rather than to adopt species-wide predictions. In an essay published by Thomas Daniels and myself called "Feralization: The making of wild domestic animals," we focused on the ways in which individual domestic animals — in this case, dogs — either become desocialized from humans, or never become socialized, and thus come to behave as untamed, non-domestic animals. These and other topics are considered in my previous essay.
I received a number of very interesting comments about my essay, and some got me to muse on how artificial selection imposed by humans past and present would give way to different forms of natural selection. Additionally, I began to think of dogs as an invasive species as they become residents of a wide variety of ecosystems because it's clear that they would have to interact -- compete and cooperate -- with members of many different species who were not created by humans but whose lives also are greatly influenced by humans. Their lives, too, would change absent us.
Biologists generally categorize different forms of natural selection as stabilizing, directional, or disruptive selection. Stabilizing selection is "a type of natural selection in which genetic diversity decreases and the population mean stabilizes on a particular trait value." For example, dog breeders generally practice artificial stabilizing selection when they try to produce dogs to satisfy breed standards. Directional selection "is a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype." A simple example would be situations in which there would be selection for body size (large, medium, or small), running speed (slow or fast), or dull or bright coloration.
Finally, when disruptive selection occurs, extremes of a trait are favored over intermediate forms of that specific trait. An example of disruptive selection, also called "diversifying selection" would be the following: "if a population of rabbits occurred in an environment that had areas of black rocks as well as areas of white rocks, the rabbits with black fur would be able to hide from predators amongst the black rocks, and the rabbits with white fur likewise amongst the white rocks. The rabbits with grey fur, however, would stand out in all areas of the habitat, and would thereby suffer greater predation." Another well-known example is Darwin's finches living on the Galápagos Islands who showed disruptive selection in beak size. Research showed that beak size "appeared to be adaptively related to the seed size available on the respective islands (big beaks for big seeds, small beaks for small seeds). Medium beaks had difficulty retrieving small seeds and were also not tough enough for the bigger seeds, and were hence maladaptive." Disruptive selection is the opposite of stabilizing selection.
Dogs going wild and reshaping nature by "reverse engineering"
If one thinks of the intensive artificial selection of dogs as a form of genetic engineering, humans surely engineered dogs for a wide variety of traits as they chose characteristics that satisfied human needs, some of which had negative effects on the dogs. As dogs go wild without us, one could view the ways in which individuals would change as a form of reverse engineering. Stabilizing selection would likely give way both to directional and disruptive selection, as for example, dogs of different sizes would likely show differential survival in different habitats, dogs of different sizes and different breeds or mixes would likely interbreed far more than they do absent human control of reproduction, and coat color, texture and other phenotypic traits would no longer be as tightly controlled without humans doing the work as dogs come to occupy vastly different ecosystems.
Will dogs become an invasive species and should they be labeled as such?
Dogs currently are creations of humans. While there are populations of free-ranging and feral dogs, individuals in these groups remain domesticated individuals. I mention the possibility of dogs becoming what some might call an invasive species because their presence, absent us, will markedly change the lives of many other animals as dogs become active members of a wide variety of populations and ecosystems. There will be changes in the behavior and geographic distribution of individuals of numerous other species, including those with whom they may form alliances and those with whom they might compete, and all of their homes will be reshaped and redecorated as dogs evolve absent humans. Dogs' genes also will enter into play, as they're able to interbreed with coyotes and wolves and produce viable offspring.
It's also interesting to note that just as humans, a pervasive -- some say the most -- invasive species, have had enormous global effects on all sorts of ecosystems, so too will dogs gone wild, and they exist because of us. Somehow, we can't get out of the picture even when we're not here, at least for the period during which dogs continue to reflect our widespread tinkering with their lives. Concerning labeling dogs as an "invasive species," when I was talking with someone, they noted with a chuckle that there won't be any humans to label dogs as "invasive," and members of other species won't be doing it either. Psychology Today writer and well-known author Mark Derr suggested to me that we might also refer to dogs gone wild after humans depart as being "abandoned" or "orphaned." Surely, both words could apply more appropriately thanks to their being "invasives." Regardless of what they're called, as time goes on, all the nonhumans who are left after humans leave need to figure out how to survive with new canine members of their communities.
Why care about how dogs would cope in a world without humans?
Many people who are interested in dogs will likely also be interested in how artificial selection will give way to different forms of natural selection when "reverse engineering" occurs without us. As we ponder what a world without humans will be like for dogs, not only do we need to focus on who dogs are, but we also need to consider the nature of dog-human relationships and the nature of dog-other animal relationships.
Please stand by for further discussions of how dogs would do in a world without humans. Each time I ponder how dogs will do without us more and more questions arise, and I'm constantly learning about all things dog including their relationships with other dogs, with other nonhumans, and with humans.
I hope that musing about what and how dogs will do in a world without humans will benefit them now as they currently try to adapt to an increasingly human-dominated world that many dogs find highly stressful. This surely would be a win-win for all, even if we'll never know what happens to them in our absence.
1Once again I thank Jessica Pierce for her help with this essay and for continuing to talk with me about what a world without humans would be like for dogs and other animals.
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