Healers cannot be built until tier 2, and even then, they are expensive to build and maintain. In the very early game, every villager matters and when one gets injured by a predator it sucks. Without a healer, they get left where they are and will certainly die.
My suggestion is, if a villager is injured and there is no healer yet, they get picked up and delivered to their house, where they have maybe a 50% chance to recover. Not great odds, but better than certain death. Same goes for injured soldiers, they are brought to the barracks to possibly recover.