No one knows for certain when dogs were first domesticated and became companions of humans.

Some research suggests that this may have happened as long as 30,000 years ago.

It is natural to assume that dogs and wolves have common ancestors and this has been documented through DNA analysis. Perhaps less aggressive wolves eventually evolved into what we now know as”man's best friend.”

In a burial site in Germany called Bonn-Oberkassel there are remains of both humans and dogs that are dated to be at least 14,000 years old.

Also at a site in China from the early neolithic period of 7,000 to 5,800 years BC there are the remains of what some consider to be earliest definite domesticated canine.

The earliest U.S. burial site that contains canine remains is in Danger Cave in Utah, and the remains are estimated to be at least 11,000 years old.

It will probably not surprise you to learn that pets can help to improve your health. In a New England Journal of Medicine article, it has been reported that “farm kids are healthier than city kids.”

Apparently, if children are exposed to germs at an early age, their immune systems are challenged and this can be beneficial or protective.

Exposure to a wider range of microbes such as those found on a farm as opposed to say city conditions seem to help the immune system develop favorably.

Children raised on farms are less likely to develop breathing disorders like asthma. Babies who have regular contact with farm animals are less likely to develop inflammatory bowel disease such as Crohn's disease or ulcerative colitis.

There is an inverse relationship between being raised on a farm and developing asthma.

The “hygiene hypothesis” states that kids exposed to certain microbes at a young age may develop a stronger immune system than those raised in a more sterile environment. In other words there are more germs in a barn to stimulate a kid's immune system.

If you don't live near a barn or on a farm, you will be glad to know that pets who are not really farm animals can help to improve your health. Kids exposed to pests tend to have less asthma, eczema and a lower risk for allergies.

Adult pet owners tend to have lower blood pressure than non-pet owners. Dog owners had a better chance of surviving during the first year after a heart attack than patients who did not own a dog.

Also, people who owned a cat at some time during their life were 37 percent less likely to die of a heart attack than those who had never owned a cat.

Dog owners may appreciate improved fitness because of the exercise gained by walking their dog as dog owners tend walk more on a weekly basis than those without dogs.

Pets in general and especially dogs tend to have a calming effect on patients with Alzheimer's disease. Maybe cave man and his cave dog started us on the right path so many thousands of years ago.

By the way, loss of a pet is never an easy experience so you can imagine my Uncle Bill's appreciation when his veterinarian called him a few weeks ago and told him of the chance to adopt a new Yorkie, his favorite type of dog.

Now Bill and his new “best friend” can be seen enthusiastically walking the sidewalks of Leesville once again.

David Keisler is a gastroenterologist and internist in Aiken.