The geography of slavery

Henry Louis Gates has a neat op-ed in the NY Times on the complexities of identifying the parties responsible for the horrible trans-Atlantic slave trade.

Gates refers to this database, where you find a treasure of maps on this subject, including the following map:

The topic of slavery is always like the topic of the Holocaust: every time I read something about these topics, I simply cannot understand how humans allowed these to happen. History is full of such atrocities, I suppose ... and, yet, even the President is so cautious about using the "genocide" word when he referred to the manner in which the Ottoman Turks practically wiped out a good chunk of the Armenians ...