Slavery tells us much about the nature of power in societies regardless of race. In Bristol during the 12th century, rich Bristolians sold their own poor into slavery in Ireland. In this white-on-white slavery, the differentiator here was not skin colour either but wealth and poverty. It is recorded that one Bishop Wulfstan campaigned against the practice of selling humans in this way and this trade later died out in the city. So the moral argument against slavery had been won several centuries before the Atlantic trade. Similarly the White wealthy exploited the White poor throughout history. In the early days of colonial expansion, the White poor, convicts, vagrants and ‘idlers’ were transported to the plantations. After Africans were deemed better suited to the climate and the nature of the work, the division of race proved a useful tool to detract from the exploitation of Whites, and reduce the likelihood of revolt and rebellion on plantations where people of different colours and cultures might would unite against their masters.

At least Christianity was used to stop slavery?

Until the 19th century Christianity was used to justify slavery like Islam was used similarly before it. The most common explanation was the Curse of Ham based on the Biblical account of how Noah cursed his son Canaan for seeing his nakedness:

“Cursed be Canaan; a slave of slaves, shall he be to his brothers.”

He also said;

Blessed by the Lord my God be Shem; and let Canaan be his slave. God enlarge Japheth and let him dwell in tents of Shem; and let Canaan be his slave

Medieval Christians believed that Ham was represented Africans. But the Curse of Ham was a powerful ideological tool that was recited throughout the territories where European enslavement of Africans was practised. There were numerous other arguments by which Christianity was made to legitimize slavery. Perhaps in secondary importance to the Curse of Ham was the notion that ‘captives in war and accredited pagans could be enslaved (Locke 15thc)’. The evangelical revival of the 18th century has often been associated with the rise of abolitionism but initially at least evangelical opinion was divided over the slave trade. Many early evangelicals actually added new ideas on Christianity and the slave trade. These attempted not just to give ideological support to the trade but to see in it as part of a higher destiny. George Whitefield for example one of the foremost Methodist evangelicals used a recurrent argument that slavery made African conversion possible when defending his purchase of a plantation and slaves in the USA. However it was not until the late 18th early 19th century that this view of slavery was ever tested.

Science proves that Blacks are inferior to Whites?

By the late 19th century new scientific ideas added and then overtook the religious rationale for slavery. ‘Scientific racism’ and imperial conquest justified and explained each other. All colonial peoples were subject to the objectifying lens of imperialism.. Racial science reinforced the negative perceptions of Blacks that had emerged in the slave trade. In 1900 for example the authors of the popular series The Living Races of Mankind wrote that:

‘The muscular development of black races is good but when considering the question of work which ‘depends only on muscle
they excel the average European; but in anything requiring judgment they are easily beaten.’

These perceptions were popularly disseminated in the school texts, by traveller accounts, and by missionary accounts. In A School History of England C.L.R Fletcher and Rudyard Kipling described blacks in the West Indies in the following manner:

lazy, vicious and incapable of any serious improvement, or of  work except under compulsion. In such a climate a few bananas will sustain the life of the #egro quiete sufficiently; why should he work to get more than this? He is quiete happy and quiete  useless, and spends any extra wages which he may earn upon finery’.

In Britain generally Blackness came to mean inferior social status.

When Caribbean migrants came to Britain after 1948 they encountered this now ingrained racial thinking that had been developing for over a century.