Shakespeare’s Source Text: Shakespeare’s main source text for the play comes from Raphael Holinshed’s 1577 The Holinshed Chronicles, a history of England, Scotland, and Ireland. 

• Mac Bethad mac Findlaich was the 11th King of Scotland from 1040–1057. He murdered King Duncan to achieve his position. Between 943 and 1097, ten of the fourteen kings who ruled Scotland were murdered in attempts to seize power. It was not uncommon or surprising for a change of rule to come about from violence. 
• In The Holinshed Chronicles, Banquo collaborated with Mac Bethad mac Findlaich to kill Duncan because Duncan was a bumbling king, unfit to rule. Shakespeare changed Banquo’s character to an antagonist to Macbeth in order to appease King James I, who came to power in 1603. James I was Scottish and thought to be related to the real-life Banquo. Thus, Shakespeare turned Banquo into a wise, noble, and morally righteous man. 

Disreputable Early Modern Theaters: In Shakespeare’s time, theater was considered low-brow entertainment. The Globe Theater and Blackfriars, the two main theaters where his plays were performed, were located outside the city walls of London. This meant they were able to challenge and subvert the crown’s laws more securely. It also meant that other disreputable forms of entertainment, such as prostitution and bear baiting, surrounded the theaters. 

• The location and culture of the early modern theaters accounts for the occasional sexual humor throughout Macbeth, especially with the character of the Porter. It also serves as comic relief in an otherwise serious play, giving the audience a chance to collect themselves before returning to melancholy ruminations on guilt.