You’re familiar with the age calculus for dogs: Multiply the number of years from a dog’s birth by 7 to have the age that equivalent to its “human age.” For instance, if your dog has been alive for four years, his age is (physiologically) similar to that of a 28-year-old person. A 10-year-old canine is about similar to a 70-year-old person.
This computation, however, is incorrect. It’s because the ratio of a dog’s aging rate to that of humans is assumed to remain constant in this computation. This is a flawed belief. When we examine the growth of dogs, we can find that they grow more quicker than people in the first several months and years. After that, the rate of growth begins to decelerate. As a result, the growth rates of a dog and a person are not linear. Rather, the following is the relationship:
A 1-year-old dog is around the same age as a 31-year-old person, not a 7-year-old human, according to this graph. A 4-year-old dog, on the other hand, is the same age as a 53-year-old person, not a 28-year-old. With time, the 7 to 1 ratio emerges, and a 10-year-old canine will eventually reach the same age as a 68-year-old person. If you wish to turn this graph into a formula, you’ll get something like this:
16 * ln (age of dog) +31
You may need to use a calculator to compute ln, which is the natural logarithm.
But, regardless of how you compute it, it makes a lot more sense than the 7:1 multiplication technique. A one-year-old dog can readily reproduce, but a seven-year-old dog cannot (if a 30-year-old human can). Similarly, humans do not always develop at the same rate as they become older; after puberty, their growth slows significantly. Dogs do not develop as quickly as they did when they were younger beyond a certain age. As a result, as seen in the graph above, a growth chart appears that develops swiftly at first but eventually slows. As a result, a dog:
- In humans, “childhood” is defined as being between the ages of one and twelve years. In dogs, “childhood” is defined as being between the ages of two and six months.
- In humans, adolescence is defined as being between the ages of 12 and 25, however in dogs, it is defined as being between the ages of 6 and 2. Development is finished at this point.
- Humans are classified as “adults” when they are 25-50 years old, whereas dogs are classified as “adults” when they are 2-7 years old.
- While people experience “old age” until they are 70 years old, dogs experience “senility” until they are 12 years old. This phase lasts till the person’s death.
Researchers from the University of California, San Diego School of Medicine looked at methyl groups in the canine and human genomes and came up with these results. Some epigenetic alterations occur in the genomes of living organisms as they age. The rise in methyl groups is the first of them. As a result, we can assess a living thing’s aging rate and more clearly discern distinct phases of development by looking at the methyl groups. Cross-species comparisons could also be feasible, as this comment illustrates!
This may be thought of as a “epigenetic clock” that can be employed in developmental biology research, similar to how there is a “molecular clock” in evolutionary biology research. Time, like the ticking of a clock, operates and exhibits its influence on our DNA as the methyl groups multiply. Scientists can identify how the physiology of a living entity evolves over time by looking at these remnants.
Of course, the aforementioned figures pertain to a certain breed of dog (in this case, labradors and other dogs of comparable size); with other dog breeds, these timeframes may vary depending on size. The epigenetic clock, on the other hand, provides a comparison for other kinds of this size.
Future study in this area may help us better understand the parallels and variations in aging processes between other animals and humans. And, who knows, perhaps it will allow us to take steps toward overcoming aging!
References and Further Reading
- T. Wang. (2020). Quantitative Translation Of Dog-To-Human Aging By Conserved Remodeling Of The Dna Methylome. Cell Systems, sf: 1-10. | Archive Link