The loss of authenticity most definitely has something to do with modern life itself (i.e. since the Industrial Revolution) though arguably goes back to the dawn of the practice of agriculture some 10,000 years ago. You ought to read, I hesitate to suggest, the Unabomber Manifesto a.k.a. "Industrial Society and its Future" by Ted Kaczynski. No shortage there of ideas on how modern man has lost his authenticity. (He also calls for violent revolution, which is just ADORABLE.)
We evolved to be hunter-gatherers in small social groups. As such, being on high alert for a faint sound, a movement in your peripheral vision, or some sign from your friends, comes naturally to us because these are traits that were naturally selected and could mean the difference between having a meal and going hungry, or between life and death. "Distraction" wasn't an issue either, because the distraction was usually the more important/urgent thing to be paying attention to, and because there weren't as many of them. We didn't have the situation we have today, where these entire natural cycles of stimulus/response/reward have been studied, and where people have figured out through years of trial-and-error, how to replicate the stimuli, and replace the rewards, in order to substitute a different response that just so happens to make them money. To the degree that you are susceptible to these stimuli you are actually being an authentic human being. It's the environment you're in that is completely inauthentic. We're all swimming in an ocean of bullshit. Being born into a world already mostly built and made for us, it's easy to forget that somebody (humans) had to come along and construct it all. Once you realize humans built it all, you then realize they had to have a reason, an incentive, maybe even an agenda. Being authentic requires reclaiming your own agenda and rejecting others' agendas where they differ from yours.