Complex sentence: At one time, historians thought her mother was an African slave on a ship captured by Lindsay's warship during the capture of Havana in 1762, but this specific date is unlikely, as Dido was born in 1761, the previous year.
Split into simpler sentences: At one time, historians thought her mother was an African slave on a ship captured by Lindsay's warship during the capture of Havana in 1762. But, this specific date is unlikely as Dido was born in 1761, the previous year.