Information About Dogs: A Vet-Backed Primer

Information About Dogs: The Short Answer

Dogs are domesticated descendants of wolves, and they've lived alongside people for tens of thousands of years. They're social and food-motivated, and they understand the world mainly through their noses. Most live somewhere between 10 and 14 years, depending heavily on size.

This guide is a starting point. It gathers the core information about dogs every owner should know: where dogs came from, how their bodies work, how they age, what they eat, and how to keep them healthy. Each section links to a deeper guide on the DearPup blog when you want more.

If you're mainly curious about the traits all dogs share, such as their senses, instincts, and personality, our guide to dog characteristics goes into those in detail. This page is the wider overview.

Where Dogs Come From

One species, hundreds of breeds

Every dog, from a 4-pound Chihuahua to a 150-pound Mastiff, belongs to the same species. Dogs are usually classified as Canis lupus familiaris, a domesticated form of the gray wolf. The huge variety you see comes from centuries of selective breeding, not from different species. Our explainer on dog species walks through how that classification works.

How long ago dogs were domesticated

Scientists still debate exactly when and where domestication happened. The AKC reports on a Stony Brook University study of ancient dog genomes. It estimated that dogs and wolves split between about 36,900 and 41,500 years ago, with domestication likely starting 20,000 to 40,000 years ago.

Dogs and wolves are still close relatives, but they aren't interchangeable. If you've ever wondered how close, read wolves and dogs: what science says and is a wolf a dog?

Dog Body Basics: Numbers Worth Knowing

A few numbers make it much easier to spot when something is off. According to the Merck Veterinary Manual, normal resting values for dogs are:

Smaller dogs tend to have faster heart rates than larger ones. Measure breathing while your dog is resting or asleep, since play and excitement push it up.

Teeth: Puppies have 28 baby teeth and adult dogs have 42 permanent ones. The AKC notes that the swap usually starts around four months of age, though timing varies.

Senses: Smell is a dog's main sense. Their vision is tuned to motion and low light, and they see mostly blues and yellows rather than the full color range we do. Their hearing picks up higher frequencies than ours. The dog characteristics guide covers each sense in more depth.

How Long Dogs Live

Size is the biggest predictor of lifespan, and the pattern runs the opposite way from most animals: smaller dogs usually outlive bigger ones. A 2023 study in Frontiers in Veterinary Science used records from more than 13 million dogs seen at Banfield hospitals in the US. It found:

• Overall: about 12.7 years of life expectancy at birth
• Toy and small breeds: about 13.4 to 13.5 years
• Medium breeds: about 12.7 years
• Large breeds: about 11.5 years
• Giant breeds: about 9.5 years

Mixed-breed dogs averaged about 12.7 years, right in line with the overall figure. For breed-by-breed detail, see how long do dogs live and our list of dogs that live the longest.

The Five Life Stages of a Dog

The American Animal Hospital Association (AAHA) splits a dog's life into five stages. The AVMA summarized the update when the guidelines were revised:

1. Puppy: birth to about 6–9 months, the period of rapid growth
2. Young adult: from 6–9 months to about 3–4 years, when physical and social maturity finish
3. Mature adult: from 3–4 years until the last quarter of expected lifespan
4. Senior: the last 25% of expected lifespan
5. End of life: a final stage defined by health, not age

Because seniority is tied to expected lifespan, a Great Dane becomes a senior much earlier than a Yorkie does. Our dog age chart helps you translate your dog's age into human terms.

Feeding Basics

Dogs need a diet that's both complete and balanced for their life stage. On pet food labels, AAFCO calls the nutritional adequacy statement the most important part of the label. "Complete" means the food contains all required nutrients, and "balanced" means they're in the right ratios. Look for a statement naming your dog's life stage, such as growth, maintenance, or all life stages.

A few ground rules cover most situations:

• Match the food to the life stage. Puppies, especially large-breed puppies, need different nutrient levels than adults.
• Measure portions. Feeding "by eye" is how most dogs gain weight. Our guide on how much to feed your dog has a starting point.
• Know the risky human foods. The ASPCA lists foods to avoid, including chocolate, grapes and raisins, onions, garlic, and xylitol. Our list of toxic foods for dogs explains why each one matters.

How Dogs Communicate

Dogs talk mostly with their bodies. Tail position, ear set, eyes, mouth, and overall posture all carry meaning, and a wagging tail doesn't always mean a happy dog. A loose, wiggly body usually signals comfort. A stiff body, a hard stare, or a tucked tail suggests stress or fear.

The AKC's guide to dog body language is a good primer. To recognize contentment specifically, see how to tell if your dog is happy.

Health Basics Every Owner Should Know

Vaccines

Puppy shots usually start at 6 to 8 weeks, with boosters every few weeks until about 16 weeks. The AKC's puppy vaccine guide notes that rabies vaccination is required by law in most US states. Your vet will tailor the rest to where you live and your dog's lifestyle.

Weight

Weight is one of the biggest health levers you control. VCA Animal Hospitals calls obesity the most common preventable disease in North American dogs. It cites a 2022 survey finding 59% of dogs were overweight, and notes that being even moderately overweight can shorten life expectancy by nearly two years.

Teeth

Dental disease is very common and easy to overlook. The AVMA says periodontal disease is the most common dental condition in dogs, and most pets show early signs of it by age 3. Regular brushing and vet dental checks go a long way.

For the full picture, see dog health: the 7 basics that matter most, and learn the early warning signs in how to tell if your dog is sick.

Practical Takeaways

• Learn your dog's normal. Know their resting breathing rate, appetite, and energy so changes stand out.
• Plan for their life stage. Puppies, adults, and seniors need different food, exercise, and vet care.
• Keep them lean. Measured meals and daily movement protect joints and add years.
• Brush their teeth. Dental care is one of the simplest long-term health habits.
• Read their body language. Most "sudden" bites or fears come with earlier signals.
• Keep risky foods out of reach. A few common human foods cause most poisoning scares.

You don't need to memorize all of this. Treat this page as a hub and come back to whichever section fits the question you have today. The DearPup blog has deeper guides on nearly every topic here.

Sources: Merck Veterinary Manual: Normal Physiological Values for Dogs · AKC: Your Dog Might Be 40,000 Years Old · Frontiers in Veterinary Science: Life expectancy tables for dogs and cats (2023) · AVMA: AAHA updates Canine Life Stage Guidelines · AAFCO: Reading Labels · VCA: Obesity in Dogs · AVMA: Pet Dental Care