Final answer:
The heavy plow in Britain was not introduced by a specific group of invaders but developed over time through various agricultural advancements, such as the three-field crop rotation and the use of draught horses.
Step-by-step explanation:
The heavy plow that revolutionized agriculture in Britain did not have a clear introduction linked to a single group of invaders. Instead, this agricultural innovation developed over time, influenced by various advancements and technologies throughout history. The concept of the plow dates back as early as 5000 BCE when metal plows were first invented, and tools for agriculture evolved from simple sticks to more complex plows capable of breaking tougher soils. While the Sumerians were notable for their early adoption of plowing technology, the particular innovation in Britain was not attributed to a specific group of invaders.
A significant leap in European farming was seen with the spread of the three-field crop rotation system and the use of draught horses, which were equipped with horse collars that allowed them to pull heavier plows efficiently. Elements like the horse collar and the heavy plow enabled the farming of heavier soils and were complemented by the increased speed and reduced need for pasture offered by horses over oxen.
Combined with other factors like the expansion of railroads, which provided supplies and equipment, agriculture in Britain and other regions experienced transformative changes that led to increased food production and the establishment of stable settlements over nomadic lifestyles. It was through an amalgamation of these advancements, rather than a single event of invasion, that the heavy plow became a significant tool in British agriculture.