# How to figure out how big your dog is

If your dog has lived alive for 10 years, then people generally think that this dog has reached old age, which is equivalent to 70 years of human rarity. This conversion factor, that is, the one-year lifespan of a dog is equivalent to seven years for humans, is obtained by dividing the average lifespan of humans (about 77 years) by the average lifespan of dogs (about 11 years).

The basic assumption of this algorithm is that, at any stage of a dog’s life, each calendar year spent is equivalent to 7 years of humanity. But new research shows that things are not that simple. If we look at some basic key stages of canine growth and development, the reason is clear.

For example, most dog breeds have reached the age of sexual maturity between 6 months and 12 months. According to the above traditional conversion, the upper limit of the dog’s age is only equivalent to the human 7-year-old childhood. At the age end of dogs, although they are rare, we know that some dogs can live for more than 20 years. According to the rule of “the conversion of a dog 1 year old equals a human 7 year old”, a dog in its 20s is equivalent to 140 years old, which is unimaginable for humans.

To further complicate matters, the length of the dog’s life depends largely on the breed. Smaller dogs have a significantly longer lifespan, suggesting that small dogs will mature and age more slowly than larger dogs.

All the above phenomena raise such a question, what exactly do we mean by age? The most obvious way to describe age is the length of time from birth to now. This is the so-called age defined in chronological order.

New research on dog life expects that pet dogs enter the middle age of dogs much faster than most dog owners think

However, there are other ways to define age. For example, biological age is a definition that focuses more on the physical condition of an individual’s subject, and mainly relies on the evaluation of a person’s physiological development index characteristics. These indicators include an “aging index” that takes into account individual disease status, cognitive impairment, and activity level.

In addition, there are more objective biomarkers of aging, such as the level of gene presentation (genes produce proteins at different speeds in different stages of life) or the number of immune cells. The rate of biological age growth depends on personal genetic factors, mental health and lifestyle.

For example, if you spend a lot of time eating junk food and smoking, less exercise and less healthy eating, then your physical age is likely to exceed your actual age. Or, if you cherish your health, you may be a 60-year-old man with a 40-year-old body.

Dog’s life mileage
Comparing the animal ages of different species, the biological definition of age is much more effective than the definition of years. Even if you know that the lifespan of a hamster is only 3 years, for a hamster that is only 6 weeks old, you will still be confused about where this hamster is in its life. But if you understand that this hamster has reached the age of reproduction, you will understand that this hamster has matured.

To measure the lifespan of a dog, it is a more accurate method to observe the DNA methylation level of the dog than to calculate the time period experienced by the dog

The simpler way to calculate the logarithm is to remember that a dog over 1 year old is equivalent to a human 31 year old

A group of scholars who have recently studied the phenomenon of life aging believe that a reasonable method for measuring the age of organisms is to observe the species’ “DNA clocks” (epigenetic clocks, which can also be translated as epigenetic clocks). DNA clock refers to a method to measure the lifespan of an organism based on its DNA methylation level. The DNA of all mammals will change the appearance of heredity with the passage of time, showing different degrees of methylation.

In the first year of life, dogs develop very quickly, and when they reach 1 year old, they are equivalent to 31 years old.

The “methylation” of DNA is especially the best indicator of biological life. The so-called methylation refers to a biochemical phenomenon in which a carbon atom combines with three hydrogen atoms, that is, a methyl group is added to DNA. Despite being different species, many significant physiological development markers, such as tooth development, appear to occur during the same period of methylation. Therefore, after comparing the DNA methylation levels of Labrador search dogs and humans, the researchers came up with a scientific formula that corresponds the dog’s age to the human age.

The formula is: human age = 16 × ln (the actual year the dog has experienced) + 31.

Ln in this formula represents a mathematical function called natural logarithm. It is well known that logarithmic functions are often used to calculate the energy released by an earthquake (magnitude on the Richter scale) or measure the sound (decibel), a non-linear digital change pattern. Natural logarithms are useful for measuring numbers that differ greatly in number. Even logarithmic charts can be used to calculate our perception of the passage of time, so it can explain why when we get older, we feel that the passage of time is also accelerating.

With this formula, this natural logarithm converts the lifespan of a dog (the dog’s age) to the human age. Studies have shown that dogs mature very quickly at first, but their aging subsequently slows down, which means that most of the life experiences of dogs are long and middle-aged.

The simpler way to calculate the logarithm is to remember that a dog over 1 year old is equivalent to a human 31 year old. After that, each time the actual age of the dog doubles, it is equivalent to the increase in the number of human years by 11 years. So 8 calendar years represent 3 “doublings” (1~2, 2~4, 4~8), which is 31 + 3×11. So an 8-year-old dog is equivalent to a 64-year-old person.

In fact, most dog lovers have begun to suspect that the corresponding age relationship between people and dogs is non-linear, because they have noticed that at the beginning, their pets matured much faster than the “1 year equals 7 years” algorithm shows speed.

The observation of life experience more refined than the rule of “1 year is 7 years old” found that the first two years of the dog’s first birth is equivalent to 12 years of humans, and all subsequent years are equivalent to 4 years of humans.

The latest human-dog age conversion DNA research method shown by the logarithmic table shows that dogs enter middle age even faster than most dog owners imagine. Dog owners need to bear in mind that when they find that their pet dog Rex is unwilling to chase the ball like the past, the life of your dog may have exceeded the life of the dog you take for granted.