DogsThe dog is unique in human history in that it was the first domesticated animal. The dog is the most widely held pet animal in human history. It has been kept for hunting, working, competition, guarding, rescue, as a companion, and more.Dogs perform several important roles forpeople, including pulling loads, herding, hunting, working, assisting police, protection, companionship, and more. Dogs have even been used in recent decades to aid handicapped persons and to detect diseases. It’s no wonder that dogs have earned the nickname “man’s best friend”.There are more than 400 million dogs in the world. There are over seven billion people in the world. Unfortunately, not everyone can have a dog. That might be agood thing, because not everyone is fit to take care of a dog.The majority of dog breeds are at most a couple of hundred years old, and people created them for important functional roles. They artificially selected their qualities and characteristics. This type of selective breeding is what is responsible for the hundreds of dog breeds we see today. There are more dog breeds comingout all the time, too. Plus, there are several hundred hybrid dog breeds, and there are at least a dozen popular designerhybrid dog breeds, such as the Chiweenie,Puggle, and Goldendoodle.Dogs range in height from six inches to 30 inches, and they come in a dizzying array of colors. Some have smooth coats, some have rough coats, and some have single coats. Some require weekly grooming, and some require daily grooming. Some dogs are loyal and obedient, and some dogs are wily and independent. Be sure to investigate each dog breed thoroughly before you settle on one that you want to own as a pet. You will have to take care of it for 12-15 years, and that includes vet bills and expenses.Dogs are very smart animals. They are capable of understanding a total of 250 words and gestures, and they can even do simple math problems. The average dog is about as smart as a two-year old kid.There are 339 dog breeds divided into tenmajor groups. Some dogs are bred to be excellent guard dogs, while others are friendlier toward strangers. There are dozens of different dynamics like these across the dog breed spectrum.