Why is the '1 dog year = 7 human years' rule wrong?

The traditional 'multiply by 7' rule is a myth because it assumes dogs age linearly, which they don't. A 1-year-old dog is sexually mature, which is much closer to a human teenager, making a 1:7 ratio inaccurate. Modern science shows that dogs age rapidly in their first two years and then the rate slows down. Furthermore, a dog's size and breed significantly affect their aging process; a small dog like a Chihuahua lives and ages slower than a giant breed like a Great Dane. A modern dog age calculator by breed uses these scientific advancements for a much more accurate result.