I'm a PHD'er and the general rule is you need a minimum of 600 - 700 calories from carbs + protein per day to provide the substrate for body maintenance and glucose production for the brain and body. A minimum of 50 gms carbs per day is recommended, with 100 more typical for normal metabolisms. The carbs should come from "safe" or low toxin starches (Theres a great pictograph of the diet on the PHD website). The rest of calories should come from fat.
I've seen Paul Jaminet recently indicating he thinks 30% of calories from carbs is optimal for longevity and health.
Personally I target about 88 gms starch/day (don't count low sugar veggies), 62 animal protein (I don't count plant proteins), and 150 gms SAT or MUFA fat. So I'm running less than the 30% recommend carb calories, working my way towards optimum. While not strictly paleo, natural foods, low PUFA, low toxin, complete macro and micro nutrition are the fundamentals of PHD.
Note that the PHD book has been revised and the new version will be out in December. I'm sure the premise remains the same but I'm eager to see the latest from the Jaminets. Following PHD and adding some starch carbs really helped with my hypothyroidism that was exacerbated by the VLC I was on before PHD.
Good luck with PHD!
15% protein, 20-40% carbs and 45-65% fats. That being said PJ does not believe in obsessing about ratios and pays far more attention to food quality. He has stated the lover carb intake may be ideal for longevity and the higher for reproductive health and physical performance.