When did rugby originate ?
The rules included : a reduction from 15 to 12 players per side a reduction from 8 to 6 men allowed on the line of scrimmage when the ball was put into play the " snap - back " system in which the ball was heeled backward from the line of scrimmage by the centre a requirement for a team to make ten yards in three successive downs or lose possession of the ball Although similar to American football rules already in place at the time , which had been developed by Walter Camp in the 1880s .