Porn: Even less Primal than Twinkies!
What's the most Primal thing of all? Wanting to spread your genes onto the next generation, obviously. From a strictly evolutionary standpoint, that's what it's all about.
So, what modern activity (a) causes young men to not want to have any sex, (b) stifles them emotionally and mentally such that no girls want them, either, (c) utterly pulverizes men's emotional resolve and mental focus, and (d) screws up your brain more than a breakfast of Twinkies and Coco Puffs screws up your gut, and (e) screws with crucial hormones like Dopamine.
"Modern grains!", you say? Yeah, I'm sure those do it, too. But the answer I was looking for is internet porn. (Which is "qualitatively different" than porn in an old Playboy rag - though that's bad, too - because of its greater ability to provide novelty, thus wildly exacerbating porn's native harms.)
At a different thread, wiltondeportes shared this epic TED Talk video which details how destructive porn is to the brain. I was riveted watching this....even though I've made it a point to avoid porn for several years, now. I can still remember how consuming it was, and can relate to much of what he describes, on a subjective level.
As a companion piece to that, here is a fiercely-written pair of articles, written by a female, detailing what porn does to you. You can almost feel her frustration at the thought of the men in her life rapid-clicking through internet porn (c'mon now, most all of us dudes have done that) like rats in an experiment clicking on the lever to get themselves heroin.