Who is a berserker?

The berserker was a category of norse warrior, tipically a mercenary or a bandit; but the main feature of those was the berserksgangr: a condition of fury that made the berserkers invincible. The colloquial expression to go berserk represent this blind fury for the battle. Many scientists think that the origin of the berserker's fury was a mix of drugs (particularly claviceps purpurea ), condition of trance (induced by religious rituals) and stress reaction for the battle (figth-or-flight ). But the study of Jesse L. Byock suggest as main cause of the berserker's fury the Paget's desease of bone .

The Paget's desease of bone

The PDB is a chronic disorder that can result in enlarged and misshapen bones. Paget's is caused by the excessive breakdown and formation of bone, followed by disorganized bone remodelling. This causes affected bone to weaken, resulting in pain, misshapen bones, fractures and arthritis in the joints near the affected bones. Often Paget's disease is localized to only a few bones in the body. The cause is unknown, but genetic factors, particularly SQSTM1 mutations , and environmental factors are important. Probably another cause of the PDB is the infection of paramyxovirus .

Paralleslism between PDB and berserker behavior

Evidences

The main signs are: ( PubMed link )
- restriction of the PDB on little area of the body ; in the case of berserker the cranial area
- major incidence in male ; berserkers were only male
- late onset ; berserkers were warrior with old experience

The beast aspect

This is probably the strongest aspect of Byock's theory. The word berserker is a mix between berr (bear) and sarkr (shirt). The possible traslation are two:
1) someone who wear bear fur
2) someone who looks like a bear
The second translation is probably the closer of the real meaning of berserker: people who suffer from PDB in cranial area develop deformities that could transform the aspect from human to beast, like a bear. In defence of this theory Byock quote the finding of the skull of Egill Skallagrimsson" , one of the most famous berserker of history known for the Egill's saga, where he is described with a big and ugly face .

Pain, fury and sleep

Another aspect is the pain caused from PTB, especially for cranial area ( PubMed link ). Probably the intense pain is the reason of the fury, also because there are two interesting aspects:
1) during the fury the berserkers fought with enemies and allies, sign of a intense pain reaction
2) after the fury, the berserkers slept for cuple of days, probably because of the absence of pain after a intense stress

Conclusion

Probably the figure of the berserker has a lot of mistery and legendary sides and obviously one single explanation in insufficient. The berserker behavior was a mix of more causes: religion ritual, drugs potion and deseases. The PTB is a interesting explanation and theory that try to bring science among the history.