In 2020, Tina Wang and colleagues at UC San Diego published the study that killed the 7-year rule. They profiled DNA methylation across 104 Labradors spanning puppyhood to old age, then aligned canine methylation trajectories against human ones — and a clean logarithmic law fell out.
What they actually did
- Measured methylation at conserved genomic sites in 104 Labradors aged weeks to 16 years.
- Compared against human methylation timelines from public datasets.
- Found dog and human clocks run at different rates linked by: human age ≈ 16 × ln(dog age) + 31.
- Published in Cell Systems with full methods for replication.
Why Labradors, and does it generalize?
One breed controlled genetic noise — good science, limited scope. The curve shape replicates across mammals, but absolute numbers shift with size, which is why honest calculators pair the formula with breed-size adjustments like ours in the dog age calculator.
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