More than a decade ago, one of the many diet trends to capture public attention was the so-called paleo diet. The basic idea was to eat plenty of meat, fat and vegetables while sharply reducing bread, grains and dairy products. Its premise was that many human diseases emerged after the transition to settled agricultural life, and that people would therefore be healthier if they returned to something closer to the diet of their hunter-gatherer ancestors. Grains and dairy products that became abundant after the rise of agriculture were pushed aside in favor of meat and vegetables — although, of course, no one was suggesting a return to the brutal struggle for survival, hunger after failed hunts or the shorter life spans of prehistoric humans. "The Perfect Primitive," a book published in March by popular YouTuber Ja Chung, whose online name is short for "self-made young man" in Korean, builds on a similar idea. The book has gone through more than 14 printings since its release. Like many books written by prominent YouTubers, its greatest strength lies in packaging a range of existing inf