Washington, United States:
A well-known "paw rule" states that you can determine how old your puppy is in human terms by multiplying its age by seven in years.
In fact, the real ratio changes over time, the U.S. National Institutes of Health (NIH) said Thursday after biological genome changes in dogs have been studied over the course of their lives.
Dogs, humans and indeed all mammals experience the same developmental schedule: birth, childhood, adolescence, puberty, adulthood and death.
Scientists have identified chemical labels on DNA that correspond to these different stages, an area of study called epigenetics.
The field is well established for humans, and some commercial companies have a DNA sample sent in to determine your biological age by reading your "epigenetic clock".
Molecules called methyl groups bind to a specific region of DNA, switch them to the "off" position, and initiate the next phase of life.
University of San Diego Trey Ideker, who was the lead author of the study published in Cell Systems, compared these patterns with wrinkles in the genome.
"I think of it more when you look someone in the face and guess their age based on their wrinkles, gray hair and other features," he said.
"These are just similar types of traits at the molecular level."
– More complex formula –
Ideker and colleagues examined the methylation patterns on 104 Labrador retrievers, the ages of which ranged from a few weeks to 16 years. These were then compared to the methylation patterns in humans.
Scientists were able to develop a more complex formula that better suits dog and human life phases – but you'll need a scientific calculator to figure this out.
The formula is "human age = 16 * ln (dog age) + 31", and you can try it yourself with Google (remember it's l for "log" and then n for "natural", all lowercase) .
If your dog is two years old, type "16 * ln (2) + 31" without quotation marks and press Enter to display "42".
Based on this formula, an eight-week-old puppy corresponds to a nine-month-old human baby – both are at the stage of developing teeth.
The average lifespan of Labradors is 12 years, which roughly corresponds to the life expectancy of humans of 70 years.
"I like getting my dogs to run and that's why I'm a little more sympathetic to the 6-year-old now," said Ideker, because his pet is the human equivalent of 60 according to the new formula.
NIH scientist Elaine Ostrander, who co-authored the study, said the new formula was developed with Labradors in mind. However, further research could include long-lived breeds – which are generally smaller – and short-lived breeds are larger.
Such watches will improve our understanding of aging between different species and help veterinarians in their clinical practice, the team said.
(Except for the headline, this story was not edited by NDTV staff and published from a syndicated feed.)