Was your fondness for dogs genetically encoded?

Analysis by Dr. Karen Shaw Becker

fondness for dogs

Story at-a-glance -

  • Researchers investigated the data of 50,507 pairs of twins and found that genetics plays a bigger role in their love for dogs than their exposure to them during childhood
  • The world’s largest twin registry — the Swedish Twin Registry — was used to find twins with known zygosity, or the degree of genetic similarity within pairs of twins
  • Narrowed the field down to 35,035 pairs, the researchers discovered that a person’s genetic make-up appears to be a significant influence in whether they own a dog later in life
  • The findings may be of importance in the future, as the genetics of the twins examined in the study may reveal more about the health benefits of dog ownership to humans over time
  • Scientists say dog owners have a lower risk of heart disease and premature death than non-dog owners, and owning a dog is linked to an improved sense of well-being, especially for single and elderly people

If you call yourself a dog lover and have maintained that position since childhood, scientists now have solid evidence that it may not have happened by chance. Growing up with a dog in your family closely influences whether you'll have a dog later in life, but your genetics also plays a part.

Researchers investigated the data of 50,507 pairs of twins for clues about whether people become enamored of dogs because they were positively exposed to them when they were children (referred to as "environmental factors"), or if the inclination toward canines is rooted in their DNA.

The study authors said their aim was to investigate the heritability of dog ownership in a large grouping of twins, so they used the world's largest registry of its kind — the Swedish Twin Registry — and used data from people born between 1926 and 1996, who were still alive in 2006. Information about dog ownership was gleaned from national dog registers from between 2001 and 2016."1

In the final analysis, information on twins "with known zygosity" was narrowed down to 35,035 pairs for scientists to estimate the heritability, unique/non-shared environmental effects and common/shared environmental effects. The upshot, according to a news release from Uppsala University in Sweden:

"The researchers found concordance rates of dog ownership to be much larger in identical twins than in non-identical ones – supporting the view that genetics indeed plays a major role in the choice of owning a dog."2

The study, published in Scientific Reports and led by Tove Fall, Ph.D., a professor of molecular epidemiology at the department of medical sciences and the Science for Life Laboratory at Uppsala University, stated:

"We were surprised to see that a person's genetic make-up appears to be a significant influence in whether they own a dog. As such, these findings have major implications in several different fields related to understanding dog-human interaction throughout history and in modern times. Although dogs and other pets are common household members across the globe, little is known how they impact our daily life and health."3

How studying twins can link dog ownership to genetics

The reason twin studies were important in the research is because it gave researchers a chance to compare both genetic and behavioral data from two people who share their entire genome. According to Twins Research Australia,4 zygosity refers to the degree of genetic similarity within pairs of twins, of which there are two types:

  • Monozygotic (MZ), or identical twins, develop when one egg is fertilized by one sperm. In the first two weeks after conception, the embryo splits in two and two genetically identical babies develop.
  • Dizygotic (DZ), or fraternal twins, occur when two eggs are released at a single ovulation, are fertilized by two different sperm, implant independently in the uterus and share about 50% of their genes, comparable to non-twin siblings.

To determine whether genetics or background tipped the scales more in regard to dog ownership in adulthood, the scientists had 15 years of records on hand. It helped that the Swedish Board of Agriculture is required to keep records on all the dogs in the country; of the 85,542 twins evaluated, 8,503 of them were found to be dog owners.

Computer models were created next so the scientists could view sets of twins and identify patterns that might point to either genetic influence or environmental factors for twins identifying themselves as bona fide dog lovers. Genetics were found to have slightly more influence; about 51% for men and slightly a higher 57% for women.

Carri Westgarth, Ph.D., a lecturer in human-animal interaction at the University of Liverpool in the U.K. and a co-author of the study, observes that the findings may be of even more importance in the future, as the genetics of the twins participating in the study may reveal more about the health benefits of dog ownership over time.

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How can dog ownership improve your health?

Animal behaviorists, psychologists and other scientists concentrating on the ways animals impact human behavior say dog owners have both a lower risk of heart disease and of premature death than non-dog owners.5 "And in patients with coronary artery disease, dog ownership is reportedly associated with improved survival."6

Owning a dog is strongly linked to alleviating social isolation and improving sense of well-being, especially for single and elderly people, a Journal of Social Psychology study reveals.7 Another advantage is that older dog owners get more exercise in because they have to take the dog outside, which is good for both of them on many levels, a meta-analysis revealed.8

Keith Dobney, Ph.D., chair of human palaeoecology in the department of archaeology, classics and Egyptology at the University of Liverpool, and one of the seven researchers, noted another aspect of their findings:

"The study has major implications for understanding the deep and enigmatic history of dog domestication. Decades of archaeological research have helped us construct a better picture of where and when dogs entered into the human world, but modern and ancient genetic data are now allowing us to directly explore why and how?"9

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