The primal diet is based on eating like a caveman. This means that you eat meat, vegetables, fruits, and fish. Dairy products, grains, and legumes are not allowed because they were only available after the development of agriculture about 12 000 years ago. The primal diet has been popular in recent years but it's been around since the 1970s. The primal diet is not unhealthy, but it may be difficult to follow because it's restrictive. It can also be expensive to follow the primal diet if you eat a lot of meat and seafood.