True, Robert Smalls was born into slavery in South Carolina and was hired out to work on steamboats as a youth. He was born an African-American slave, and during and after the Civil War became a ship's pilot, sea captain, as well as a politician. He freed himself, his family and other slaves and convinced Lincoln to let African-American soldiers fight during the war.
In an explanatory essay, or any essay, the introductory paragraph introduces (hence it's name) the main idea, or what you are going to explain. The body paragraphs go into extreme detail of what the introductory paragraphs mentioned.
It caused many people to die younger and more frequently since they didn't have immunity/vaccinations
