Ladies and gentlemen, allow me to introduce to you the Sudanese hug.

While working on an archeological excavation in northern Sudan, I was fascinated by a form of greeting I had never seen before. Two men would each clap his right hand down on the other’s left shoulder. They might pat each other’s shoulder a few times while smiling and exchanging greetings. And then the arms would drop and the men would shake hands.

Curious about this custom, I asked the dig director about it. He told me it was the “Sudanese hug,” and he suggested I ask Mahmoud, the Sudanese government representative who minded our excavation, to explain it. Mahmoud had spent time at academic conferences in Europe and was aware that the Sudanese hug was unfamiliar to most foreigners.

“When you greet a friend,” he explained, “and maybe you are not family, so you do not want to hug him, but you are not just business acquaintances, so you want to show more affection, then you do the Sudanese hug.”

This was a revelation.