Excavations of Viking latrine pits have revealed that these populations suffered massive worm infestations. The way that their genes developed to protect their vital organs from disease caused by worms has become the inherited trait which can now lead to lung disease in smokers.

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Excavations of Viking latrine pits have revealed that these populations suffered massive worm infestations. The way that their genes developed to protect their vital organs from disease caused by worms has become the inherited trait which can now lead to lung disease in smokers.