Why did the english crown keep slavery in their colonies ?

The reason for this was because having slaves was cheaper for factory owners and produce owners compared to having people who they would actually pay, which in turn made them earn more money.

And because the people from England who represented workers' rights weren't present in their colonies, they didn't know nor had access to knowledge on the misstreatment of these workers and couldn't help them for that reason. 

It depends on what you believe, if you’re christian that you would have been told that the first humans were created by god and that we’re all decedent's from adam and eve but scientist say otherwise