Which advancement in science most contributed to the successful colonization of Africa by European powers in the late 19th century?

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."

Jeez. That whole time period was so messed up

explanation:

a trial judge has broad powers in his courtroom. the judge's decision is usually final for the duration of the trial, and the party's one special type of witness is an expert witness.