More like 2-3 times shorter. Humans have barely gone past 30 years of age for most of the last 10k years, and I don't see how dogs' lifespans were improved in recent centuries.
Humans lifespan was that low since the high mortality rate the first months of life. After the first years, the expected lifespan increased dramatically. A humans need a few years to be able to reproduce and those who were able to have a longer lifespan. Even if the dogs didn't improve their lifespans (which honestly, I doubt they didn't) we are still in a similar ratio.