On New Year's Day 2011, I flew to Lagos to research human trafficking in Nigeria. Towards the end of my trip, I visited a small town called Badagry, about a two-hour drive west of Lagos. In 1502, Portuguese colonists built one of the first slave-trading posts along the coast of West Africa in this city. The non-descript, two-story building still stands today as a museum, but for more than 300 y…