Is it true that one dog year is equal to seven human years?

It is generally accepted that to calculate the age of a pet by human standards, you need to use a factor of 7. We checked whether this is true.

The idea of ​​such a ratio is widespread among the people. On the Internet you can read about it on general websites (“Arguments and Facts”, Biological dictionary, Allcalc.ru), and on resources dedicated directly dogs. Science popularizer Michio Kaku writes about him in his book "Physics of the Future". Among famous writers, a similar proportion was mentioned Louis Aragon, Victoria Tokareva, Eduard Uspensky and many others.

Let us immediately note that comparing the ages of a person and an animal is a very conditional thing. "A dog's age in human years" is generally understood to be the age at which a human is typically at the same stage of development as the dog in question. In addition, we are not talking about the individual developmental characteristics of a particular individual - average indicators are taken into account.

Scientists have been talking about the fact that it is incorrect to correlate dog age with human age using a linear coefficient for quite some time. In 1953, French veterinarian Albert Lebeau proposed theory, taking into account the accelerated development of dogs in the first 12 months of their life. According to his calculations, a dog that reached sexual maturity at the age of one was equivalent to a 15-year-old teenager. During the second year of a dog’s life, its body undergoes additional formation, so a two-year-old dog already corresponds to the physiological state of a 24-year-old young man. Each subsequent year of a dog’s life is equivalent to four human years. Thus, a three-year-old dog is 28 years old by human standards, a four-year-old dog is 32, an eight-year-old is 48, etc.

And although the Lebo table is still widely used, it does not take into account one important factor - the dependence on the breed, or more precisely, its average size.

After all, back in 1932, the Swiss biochemist Max Kleiber derived law metabolism in animals. After conducting a lot of experiments, he came to the conclusion that large animals live longer. Oddly enough, in the case of dogs, this law works exactly the opposite: St. Bernards and Labradors, contrary to the Swiss’s calculations, live 10-12 years, and Pekingese - 14-16 years. At the same time, at the same moment in time, their “human” age differs, and the older they get, the stronger the difference in biological age grows. These days, the following table, based on the average weight of an adult, is very popular among veterinarians and dog handlers:

Finally, in November 2019, scientists at the University of California published study, which offered a completely new perspective on age. In their opinion, instead of counting calendar years, it is much more useful and accurate to look at changes in a dog's DNA. Experts believe that biological age should be calculated using the so-called epigenetic clock - a set of epigenetic DNA marks that accumulate over time in the body of any mammal.

Many important physiological markers (such as tooth development) appear in different species at the same level of modification of the DNA molecule. By comparing levels of this process, called methylation, in Labrador Retrievers and humans, the researchers developed a formula that could relate a dog's age to its human equivalent. The formula is: dog’s “human” age = 16 x ln (dog’s own age) + 31, where ln is natural logarithm, that is, the logarithm to the base e.

Here's how this formula works graphically (red curve):

As we can see, dogs mature very quickly at the beginning of their lives (which was confirmed by previous studies). Then their aging process slows down, and our pet spends most of his life in a state of middle age. However, in contrast to the previously held opinion, the first dog year is approximately equal to not seven (green curve) and not 12–15 (blue curve), but 31 human years. At the same time, scientists note that, despite all the differences between the breeds, the trajectories of their development are similar to each other.

Perhaps this study does not put an end to the question that interests us. However, it can be unequivocally stated that, according to the modern point of view, coefficient 7 when calculating the age of a dog in human years is incorrect - the relationship here is clearly non-linear.

Not true

What do our verdicts mean?

Read on the topic:

1. Your dog's human age: a new scientific formula for calculating
2. Quantitative translation of dog-to-human aging by conserved remodeling of epigenetic networks
3. Comparative Longevity of Pet Dogs and Humans: Implications for Gerontology Research