On the mystery cloud of AD 536, a crisis in dispute and epidemic ergotism: a linking hypothesis

In AD 536, some kind of natural catastrophe(s) darkened the sun by what has been called a mystery cloud or a dust veil. The darkening of the sun lasted for over a year and initiated dramatic changes of the climate in the Northern Hemisphere,resulting in a series of cold ‘years without summer’. This climatic disaster has been linked to the so-called Migration Period crisis in Scandinavia, a time of population decline and reforestation of agricultural land. The extent of these changes and the relative importance of possible factors involved are matters in dispute; failed harvests and famine, plague, war and social changes have been discussed so far. The present comment puts forward the hypothesis that epidemic ergotism due towidespread contamination of food and fodder by poisonous ergot (Claviceps purpurea) also may have been a contributing factor. The main reason being the extreme weather conditions, which became exceptionally favourable for growth andspread of this highly toxic fungus in crops and pastures for several years in a row after the AD 536 event. It is pointed out how the ecological and toxicological characteristics of ergot are consistent with an irregularly distributed depopulation, aneed of several generations for recovery, an extensive reforestation of agricultural land and migration of settlements from lowlands to higher grounds. It is also argued for the possibility that the wording in two verses of the Old Norse poemVöluspá actually was inspired by long-time memories of illness due to ergotism