John Howland may not be as famous as William Bradford, John Carver and Myles Standish, notable passengers on the Mayflower that landed in Massachusetts in 1620. Yet Howland, who boarded the ship as Carver's servant, probably had a greater impact on the history of the United States than any of them. Hundreds of thousands of Americans will sit down for Thanksgiving dinner Thursday unaware that they owe their very existence to Howland, who almost never even made it to the New World. Howland fell overboard in the middle of the Atlantic during a gale