What Examples Do You Know of Ancient Racism

Harappa. Miniature Votive Images or Toy Models, ca. 2500. Hand-modeled terra-cotta figurines with polychromy. Brooklyn Museum.
CC Flickr User Amy DreherI received an email that, in effect, asked me for additional examples of ancient racism. Additional, because he had already used the Aryan invasion to prove his point that even if the word "race" is modern, the concept behind it was not. Although he thought the Aryan invasion was adequate:

"It takes only one example to sink the claim, and I have used the example of the Aryan invasion of India and the ensuing imposition the caste system, largely along lines of skin color...."

he thought it would be better to have examples from elsewhere in the ancient world. There are problems with his lead example. Here are some articles on the topic:

• Who Were the Aryans?The Aryan Invasion Mythby K. Kris Hirst, About.com Guide to Archaeology
• The Indus Valley CivilizationWhat We've Learned About the Indus Valley in the Last Century
• Errors in What We've Learned About the Indus Valley
• 'Empires of the Silk Road'
• 'The Invention of Racism in Classical Antiquity'

If this is an area you've actually studied, please cite examples of racism in the ancient world or academic articles on it, politely, and without referring to the modern world, where modern refers to events after the Fall of Rome in the West (A.D. 476).