Edward I, as we have seen, had helped to crystallize this practice of primogeniture and entail, whereby the family lands as well as the title went intact to the eldest son. The younger sons were commoners with no automatic social rank or privilege beyond what they might achieve for themselves, and were free to carry their inheritance of class - often their only heritage - into many diverse fields. It was through them in particular that the English social system came to possess more flexible features than the Continental. In France, and else where on the Continent, every son of a nobleman was a nobleman, also, rigidly limited by caste in the occupations which he might select. The class thus increased in geometric ratio, until in Poland, as an extreme case, it was estimated that there was a nobleman for every four acres of land.
(from A History of England and the British Empire)