I was wondering whether Europeans already had racist viewpoints when the slave trade started, or did this spread later on. Was it propagated to justify the slave trade which brought in huge profits for many? I know that even when the Americas were discovered the natives were treated as savages, but was this purely because of their lifestyle/non-christian beliefs or were these ideas of "lesser humans" already developed?
I am aware that this may be a kind of a "chicken or the egg" question but I would like to hear the opinion of someone more knowledgeable on the topic.
Unfortunately, I'm a bit pressed for time at the this minute to write up a fresh reply, but I would like to direct you to these answers I've written before in response to similar questions which you might find helpful:
In essence, it is the experience of the African slave trade and slavery in the New World that gives rise to racism proper from the 16th Century onwards. It isn't, however, quite as straight-forward as racism emerging as just an ex post facto justification for slavery; the relationship is a little more complex than that. From the beginning, you can see the roots of what will become racial stereotypes rooted in cultural and religious differences, which slowly but surely collapse together into associations with skin colour and ideas of racial classification. Whilst justifying slavery is absolutely a factor, the gradual emergence of racism also helps to promote the institution of slavery; it's a vicious cycle where one reinforces the other, to the point where it is difficult to unpick them. One of the great debates in the historiography of slavery in North America is at what point 'race' becomes the deciding factor in determining your status (socially, at least; legally, that process really begins in the 1660s).
I'm not an academic, but you should probably check out Ira Berlin's Many Thousands Gone where he writes about the first two centuries of slavery in North America.
Berlin's answer to your question is that racism as we know it today was spread after slavery was well underway by North American slavers to continue to justify the business. The specific line he draws is when race laws started being created. Slavery prior to this point was organized by war, religion, debt, and other mechanisms. It was the Americans who introduced the principle that the color of your skin was what made you a slave.
How this translated into racism is hard to mark with a specific date, but as the various southern colonies began to have more slaves than white people, it created a very intense culture of paranoia. This was bolstered by uprisings and massacres in the West Indies. The whites were scared their slaves were going to kill them all and this produced a lot of culture, ideas, and practices that worked around defining an entire race as the Other. This, in turn, created more race-based laws. Which created more fear and paranoia for white people. See Southern Honor by Bertram Wyatt Brown
That's the history of it, anyways. You might want to post this in a sociology or anthropology subreddit.
Again, I'm not an academic. Just pointing out what some respected sources said.