Chiral Mirrored food; those time travelers cannot come to this time until similarly chiral mirrored food is available. They are mirrored clones. The loophole; the law say no 'human' can time travel, unless sanctioned by the state.
Zombies; big problem. Maybe this is how aliens control the human species, by creating mirrored clones and send both 'type' fighting each other; mirrored vs non-mirrored.
Zombie! Zombie! Zombies!
P.S. Chiral mirrored zombies should not be eating non-mirrored babies. Non-mirrored, normal beings should not be eating cloned mirrored fish. The proteins can be digested and absorbed but it is not compatible and will rot. Brain rot. For all types mirrored or non-mirrored beings, cannibalism invites Kuru disease, prion diseases, etc. Cannibalism is not natural for human being, mirrored or not.
