Answer: Steam power, which lead to steam powered ships helped European forces colonize Africa.
Explanation:
Steam Powered ships aren't the only thing though, and I think they're kinda tied in 1st place with guns for "Scientific advancement that most helped Europeans colonize Africa". I think-- I could be wrong, but I'm pretty sure-- they had machine guns at that point. Let me just double check that so I don't mess you up.
Yup! They had the maxim machine gun which "allowed Europeans to wipe out Africans in battle after battle."
