Originally, the story was going to center around Edward growing up around pirates in the span of about 20 or 30 years, starting when he was 12 in the William Kidd and Henry Avery era (around 1699) and go on into the Blackbeard era (around 1716). Since both Ezio and Connor went though a similar idea (with mixed results from the fans and developers), they decided to only focus on about a decade starting in 1715, so that Edward is a young man all the way though the game, but still have him go through a tremendous arc.