Britain needed to resolve a conflict between the principles of free trade (which Britain was more and more adopting) and the institution of slavery.
Concerns about slave revolts indeed were indeed part of Britain's pragmatic decisions to end its participation in the slave trade in 1807 and phasing out slavery in its empire starting in 1834. But the other factor was that the Industrial Revolution was taking over how the British economy operated, and the institution of slavery no longer fit within the new, industrializing economy.
Along with those practical reasons, there was of course much moral pressure applied by the abolitionist movement. William Wilberforce was a key voice of conscience in Parliament from the moral side of the argument.
They achieved unification in the 19th century!
The surplus of food lead to everything you see today all because people could settle down and make towns then civilizations and eventually empires
