Pemmican
en.wikipedia.org
en.wikipedia.org
Once my group went super high mileage, we just took tea, rice, vitamins (electrolyte powder wasn't popular yet), and iodine for water treatment. It's amazing how far you can go in a couple of weeks if you're willing to wear river-washed clothes, eat flavorless food, and lose 10-15 pounds in a go.
I'd always carry a can or two of spam, though. Ten or twelve days in, the guy with the salty canned "meat" is a bonefide hero.
that's metal, thinking about processing marrow kind of gives me the creeps though