Street dogs survive without humans — Could yours?

Analysis by Dr. Karen Shaw Becker

dog domestication affects survival skills

Story at-a-glance -

  • To survive in a world without humans, our dogs would need to reacquire survival skills lost to domestication
  • Domestication has also led to genetic changes that would inhibit dogs’ ability to survive in the wild
  • The fertility and overall health of dogs has also diminished as a result of domestication

Those of us with dogs in the family can't imagine life without them, but after thousands of years of domestication (anywhere from 10,000 to 40,000, depending on who you ask) could our dogs live without us? Has their ability to survive in the wild been traded for skills like understanding and interpreting human words, moods and behavior?

What skills would your dog need to survive in the absence of humans?

The domestication process has resulted in dogs being highly dependent on humans for all the necessities of life including food, water, shelter, safety, exercise, playtime, affection, health care and more. Without us, writes veterinarian Dr. JoAnna Pendergrass, " … dogs would be faced with a world in which they would have to completely fend for themselves to eat, stay safe and ultimately survive."1

Since around 80% of the dogs in the world are free-ranging,2 humans could disappear from the earth and it wouldn't matter much to them.

But for the remaining 20% of pet dogs, writes Pendergrass, life without humans "… would require having some survival skills, such as forming relationships and alliances with other animals (even cats!), having an independent personality, being street-savvy, being able to rapidly adapt to changing conditions, and having a willingness to take some risks."

Skills like finding shelter from the weather and predators would involve trial-and-error as domesticated dogs honed their ability to survive in the wild.

It's possible that medium and large breed dogs would have an easier time of it than very small or giant breeds. Pendergrass also believes dogs would need to breed with other animals, in particular, coyotes and wolves, in order for them to survive longer-term in a human-free world. Interbreeding would produce future generations that could survive and thrive without humans.

Domestication has led to genetic changes that could hamper dogs' ability to live successfully in a world without humans

"Domestication syndrome" is a term Charles Darwin coined to describe his discovery that "domesticated mammals possess a distinctive and unusual suite of heritable traits not seen in their wild progenitors," according to a 2014 study published in the journal Genetics.3 For example, picture a wolf, and then picture a dog with floppy ears, a sweet little patch of white fur and a baby (puppy) face.

Domestication syndrome isn't seen exclusively in mammals like dogs, rabbits, foxes, pigs, horses or sheep — it has also been observed in domesticated birds and even fish. Scientists, including Darwin, have long been puzzled by why domesticated animals have many similar features and behaviors. These include:

Depigmentation (white patches, brown regions)

Floppy ears

Smaller ears

Shorter muzzles

Smaller teeth

Docile behavior

Smaller brain or cranial capacity

More frequent estrous cycles

Juvenile behavior

Curly tails

According to the authors of the Genetics study, when certain species are domesticated with the goal of taming them, it leads to genetic changes that affect a group of embryonic stem cells called the neural crest.

Neural crest cells form near the spinal cord of early vertebrate embryos. As the embryo develops, the cells travel to other locations in the body and create different tissue types, including pigment cells, parts of the head (skull, jaws, teeth, ears) and the adrenal glands, which are responsible for the fight-or-flight response. Neural crest cells are also indirectly involved in the development of the brain.

Lack of fear of humans had its start as a cell abnormality

According to the Genetics study co-author Adam Wilkins, Ph.D., of Berlin's Humboldt University:

"When humans bred these animals for tameness, they may have inadvertently selected those with mild neural crest deficits, resulting in smaller or slow-maturing adrenal glands. So, these animals were less fearful."4

The neural crest abnormalities Wilkins speaks of could also lead to physical signs of tameness — and not all of them good. For example, floppy ears are an appealing feature on dogs and rabbits, but unfortunately, they're actually the result of deformed ear cartilage. Animals with ears flopped over and hanging alongside their faces presumably don't hear as well as those with erect ears.

Domesticated animals also appear to have smaller brains than their counterparts in the wild. The decreased size of the forebrain seen in most domestic animals could be indirectly related to neural crest changes.

Domestication has had a negative influence on the fertility and health of dogs

A 2015 study conducted by biologists at the University of California, Los Angeles (UCLA) suggests that human domestication of dogs is responsible for creating certain harmful genetic changes.5

Tens of thousands of years ago, gray wolves were domesticated by humans through artificial selection and inbreeding. Many experts in the field have long believed that not all the genetic changes that occurred as a result of domestication were desirable, however, little research has been done to evaluate the effects of such human interference on dog genomes.

For the study, the UCLA researchers collected complete genome sequencing data on 90 canines, including 19 wolves, 25 semiferal "village dogs" from 10 different countries and 46 domesticated dogs across 34 different breeds. The research team analyzed genetic variations among the different groups, looking specifically for markers that were deemed detrimental and would be extinguished in the natural world so as to not affect future generations.

The researchers learned that the dogs had approximately 115 more such markers than the wolves. They speculated the difference was probably due to "population bottlenecks" associated with domestication, coupled with aggressive breeding programs.

Population bottlenecks, which are temporary reductions in populations, lead to less diversity, which in turn can lead to harmful gene mutations that persist from one generation to the next. The researchers also discovered that lack of diversity seems to have resulted in dangerous DNA changes in isolated groups of wolves as well, including Isle Royale wolves and Tibetan wolves.

The bottom line for domesticated canines? Dogs with less ability to reproduce than wolves, and a higher risk for certain disorders including asthma, arthritis, eye diseases and certain cancers.

The researchers suggest that increasing diversity in dog populations would allow the negative genetic changes to disappear naturally over time. Conversely, maintaining the current practice of selective breeding of dogs from small populations will lead to even more problems in the future. Kirk Lohmueller, Ph.D., senior study author and assistant professor of ecology and evolutionary biology at UCLA, observes that:

"… The use of small populations artificially bred for desired traits, such as smaller body size or coat color, may have led to an accumulation of harmful genetic variations in dogs."6

These types of variations, according to Lohmueller, may at some point lead to a number of different developmental disorders and other health risks. He suggests that selective breeding programs — especially those designed to conserve rare and endangered species — may need to involve large populations to weed out detrimental genetic changes.