Cavemen were gathers before they began hunting. After that they were hunter-gatherers. They ate fruits, wild greens, roots, nuts and seeds. There are most definitely carbs in those. If you are not eating some carbs you are not healthy. You don’t need a lot unless you are very active and definitely do not need manufactured carbs but you do need some carbs in your diet to survive.
Though its light weight and long shelf life are ideal for navigating harsh conditions, freeze-dried food is probably most famous as a cultural curiosity: Like many Americans, I discovered it in a museum gift shop, gawking at the styrofoam-like ice cream that astronauts used to have for dessert. More recently, I encountered it at a disaster preparedness convention in Raleigh, North Carolina, where smiling, gray-haired preppers manned tables piled with plastic bags full of vegetables, meats, and stews.