The first civilization started in Mesopotamia around 5000 BCE (more or less), which is 7,000 years ago. If you live until age 80, that's more than 1% of the history of civilization.
Just throwing it out there for anyone else who'd never thought about it before. Certainly changed my perspective a bit.
The population of nomadic humans was lower, but there's evidence that they were much healthier than those who settled down to grow crops full-time. Agriculture was a win because it allowed for many more people to be born, but it's not a life for which we're well adapted.
ADDED: If this guy is right, 99% could turn out to be an underestimate or an overestimate: