The Science Behind Man’s Best Friend: Domestic Dogs

Name another species more universally loved than the domestic dog. I’ll wait… I didn’t think so.

Around the world, where you find us – Homo sapiens – you won’t have to look far to find the pet dog – Canis lupus familiaris.

From Chihuahuas to Great Danes, these legged puppies come in a dizzying array of shapes, colors, sizes and temperaments, but where did they come from?

Domestic dogs evolved from an ancient, now extinct wolf. The researchers have valuedusing genetic analysis, that dogs and wolves diverged around 27,000 to 40,000 years ago.

But exactly when, where and how many times dogs were domesticated by humans have puzzled scientists for decades.

The domestication of the dog

Scientists know that domestication occurred in Eurasia and that dogs were mankind’s first domesticated animals – predating agricultural animals like the goat and sheepabout 10,500 years ago.

The oldest undisputed fossil of a domestic dog dates back approximately 15,000 years, from one site to Bonn-Oberkassel in Germany, where archaeologists found a 28-week-old puppy buried next to grave goods and two humans. And while the dog remains have goes back more than 30,000 years agotheir dog or wolf status remains very controversial.

Part of the right half of the lower jaw, fragment of the upper jaw and teeth of the dog from the Bonn-Oberkassel grave. Credit: Thilo Parg/Wikimedia Commons. License: CC BY-SA 4.0

There is no consensus as to exactly why and how our pooches were domesticated, but there is a some assumptions.

Some scientists suggest that cooperative hunting between wolves and humans led to domestication, with humans using wolves as tools to hunt megafauna. Another hypothesis suggests that humans may have captured and tamed wolf cubs, raising them to adulthood and breeding them to eventually domesticate them.

Read more: Two Ancient Wolf Populations That Evolved To Be Man’s Best Friend

But the dominant assumption is that wolves have essentially domesticated themselves, invading human settlements to feed on animal remains and other edible waste. Over several generations, they would have become progressively bolder and less fearful of humans, benefiting humans as guards or hunting partners by living alongside them.

How did we get to today’s dog breeds?

Since domestication, humans have selectively bred dogs for desirable traits. Choosing dogs and their companions to replicate useful traits, like reduced aggression and increased social ability, or aesthetic traits like coat color or floppy ears, means that over time these traits become more prevalent in some populations.

This year, researchers found that humans may also have unconsciously selectively bred dogs to have more expressive faces.

Drawings and carvings depicted different types of dogs for millenniabut that’s only the victorian era in England that dog breeds were first recorded and codified. It was with the advent of competitive dog shows that new rules of controlled breeding were introduced, to produce a more uniform look for each breed, with dogs that perfectly represented the physical characteristics of their breed being rewarded at show. .

Over time, this is how we ended up with the 356 different breeds of dogs recognized by the International Canine Federation today.

Read more: The origin of dog breeds revealed

Dogs have a remarkable sense of smell

It is due to several physiological factors. Some breeds, such as bloodhounds, have up to 300 million olfactory receptors, while we humans only have about 6 million.

Their anatomy also evolved to separate the functions of breathing and smelling when they inhale, thanks to a fold of tissue just inside their nostril. When dogs inhale, the airflow splits into two different pathways: one continues into the lungs for breathing, while the other is reserved for smelling.

Dogs – but not humans – have an olfactory recess to house their olfactory receptors. When dogs inhale, approximately 12% of the air moves through this special region at the back of the nasal cavity.

When they exhale, the air leaving the lungs bypasses this area entirely, leaving the fragrant air untouched to give the odors more time to be absorbed. Exhaled air exits through the slits on the sides of their nostrils and the way the air swirls around actually helps bring new scents to the dog’s nose, allowing them to sniff almost continuously.

They even have movable nostrils, which allows them to determine the direction of the smell.

And amazingly, they can detect changes in human physiologywhich is possible because illness and disease cause changes in the profile of gases – known as volatile organic compounds – emitted by our blood, urine, feces, skin and breath.

Medical Alert Service Dogs Can Identify Blood Sugar Changes in Diabetics, and a 2021 study found that dogs can detect epileptic seizures from sweat samples.

Recent studies have even shown that dogs can accurately detect certain cancerand infections like malaria and COVID-19[feminine].

This year, a small study even found that dogs could distinguish when people were stressed, accurately detecting breath and sweat samples from stressed participants 93.75% of the time.

Read more: New Study Suggests Dogs Could Smell When We’re Stressed

Did you know that dogs are colorblind?

When light hits a retina in the eye, it triggers chemical changes in the cone cells, which react differently to different wavelengths of light.

Humans have three types of cones, which means we have trichromatic vision and can see all wavelengths of light in the visible spectrum as distinct colors.

But a 1989 study found that dogs only had two types of cones in their eyes. Then a 1995 analysis of canine vision has determined that these two types of cones are sensitive to wavelengths which, in the visible spectrum, correspond to two different hues: one in the range of violet and blue-violet light (length of wave of 430 to 475 nanometers), and the other in the wavelength range of greenish yellow, yellow and red light (500 to 620 nm).

So, from a dog’s perspective, the world is a mixture of yellow and blue. For wavelengths between these two extremes, colors would appear less saturated, like mixtures of white or gray.

Read more: Dogs are colorblind

No matter where they’re from and how long they’ve been with us, we can all agree that dogs make our lives better to be in them.

Bette C. Alvarado