The Galatians were not literally biting and eating each other. They were not engaging in cannibalistic behaviour. Instead, they were fighting, criticizing each other in public, encouraging rivalries and division. It is possible that they were subject to party factions similar to the church in Corinth (see 1 Corinthians 1:10–13).1
15 But if you bite and devour one another, watch out that you are not consumed by one another.