A professor from American University in Cairo says discovery of prostate cancer in a 2,200-year-old mummy indicates the disease was caused by genetics, not environment.

The genetics-environment question is key to understanding cancer.

AUC professor Salima Ikram, a member of the team that studied the mummy in Portugal for two years, said Sunday the mummy was of a man who died in his forties.

She said this was the second oldest known case of prostate cancer.

"Living conditions in ancient times were very different; there were no pollutants or modified foods, which leads us to believe that the disease is not necessarily only linked to industrial factors," she said.

A statement from AUC says the oldest known case came from a 2,700 year-old skeleton of a king in Russia.

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