Perhaps it is neither gender. For the witches, the "evil sisters," are aberrations of Nature. For instance, in Act I, Scene 3, Banquo remarks to the witches,
What are these/So withered, and so wild in their attire,/That look not like th'inhabitants o'th'earth,/And yet are on 't?/Live you, or are you aught/That man may question? You seem to understand me,/By each at once her choppy finger laying/Upon her skinny lips. You should be women,/And yet your beards forbid me to interpret/That you are so. (I,iii,39-47).
Clearly, these preternatural beings are neither male nor female. There is a duplicity of their character as much as there is of their powers. Prophets of the future, custodians of evil, or something more neutral as creatures who know the future, but can do little to change it--they have been interpreted in various ways.
Likewise, Lady Macbeth, too, becomes an aberration of Nature. For, in her desire for Macbeth to acquire power she unsexes herself in order to provide her husband with the courage to realize his ambitious desires. The scene in which she "desexes" herself is one of the most frightening expressions of preternatural evil:
...Come, you spirits/
And fill me, from the crown to the toe, top-full/Of direst cruelty! Make thick my my blood,...Come to my woman's breasts,/And take my milk for gall,you murd'ring ministers....(I,v,41-48)
Like the "weird sisters," Lady Macbeth has a duplicity of character, although hers differs in manner. She is treacherous: She is the gracious hostess to Duncan whose murder she catapults Macbeth into committing.
The element of the supernatural and the preternatural play contribute more to the role of evil than the element of gender. Even Macduff, who finally ends the reign of evil by slaying Macbeth is an unnatural man, for he is "none of woman born."
as is Lady Macbeth.
Even if we agree that the witches are responsible for Duncan's murder, and later for Macbeth's undoing through the apparitions' equivocations, the gender question is still not so simple to settle. On their first appearance, Banquo is surprised to see that the witches grow beards though they seem to look like women.
Lady Macbeth, who prepares the blue-print of Duncan's murder and goads her husband to the crime, assumes a cruelty which is traditionally associated with the male rather than the female sex. Lady Macbeth's decision to stand by her husband's evil ambition and her volition to be a party to conspiracy and wickedness may suggest the surrender of the female identity to male ambition, typical of feudal patriarchy. In that sense, Lady Macbeth is like the witches--female in appearance, but male in reality. The woman in Lady Macbeth in conflict with her assumed maleness causes her sufferings ever since Duncan's murder.
The 'hurlyburly' that the witches refer to in the opening scene may also be an over-turning/confusion of gender identity in Macbeth. The only true woman is Lady Macduff, but she is one of the play's worst victims.
Shakespeare gives many signals that the tragic events of Macbeth are due to a stereotypical and unnatural maleness. The witches, for instance, although supposedly women, have departed from the traditional attributes of that gender in behavior and even in appearance. As Banquo says in Act I, Scene 3, when he and Macbeth meet the witches:
You should be women,
And yet your beards forbid me to interpret
That you are so.
In the same way, when Lady Macbeth decides that murdering Duncan is a good idea, she explicitly renounces her gender and all its attributes, becoming "manly" rather than "womanly" through an act of will driven by ambition. In Act I, Scene 5, she declares
Come, you spirits
That tend on mortal thoughts, unsex me here
And fill me, from the crown to the toe, top-full
Of direst cruelty! Make thick my blood,
Stop up the access and passage to remorse,
That no compunctuous visitings of nature,
Shake my fell purpose nor keep peace between
The effect and it! Come to my woman's breasts,
And take my milk for gall, you murdering ministers,
Wherever in your sightless substances
You wait on nature's mischief! (my emphasis)
To carry out the murder, she must leave behind the attributes of her gender. Later, when she is urging Macbeth on to the deed (Act I, Scene 7), she taunts him by suggesting a failure to move would be unmanly:
When you durst do it, then you were a man;
And, to be more than what you were, you would
Be so much more the man.
She goes on to again renounce the attributes of her gender in the most violent way she can imagine:
I have given suck, and know
How tender ’tis to love the babe that milks me:
I would, while it was smiling in my face,
Have pluck'd my nipple from his boneless gums,
And dash'd the brains out, had I so sworn as you
Have done to this.
Given all the signals that Shakespeare thus left that the female characters complicit in Duncan's murder had left or were contradicting or betraying what was proper to them, it seems very hard to insist that females or femaleness is responsible for the events of the tragedy. What is responsible is rather both men and women adhering to a perverted view of what is manly, strong, and resolute.
In Shakespeare's tragedy "Macbeth," it obviously the female sex that is more responsible for the tragic events in the play. It is the female witches who first give Macbeth the premonition that he will be King, and egged on to kill Duncan by Lady Macbeth, Macbeth does "get the ball rolling." Without the premonition from the witches, or the goading by Lady Macbeth, it is apparent that Macbeth would not have killed the King.
The witches first agree to meet Macbeth when the Third Wich says, "There to meet with Macbeth [upon the heath] (i.i.8) and when the witches do meet him, they give him the premonition that he is the Thane of Glamis, Thane of Cawdor and "Macbeth ...shalt be king hereafter"that (i.i.49-51).
Lady Macbeth tells Macbeth that he "shall put this night's great business into my dispatch," meaning that he should leave everything to her to make sure that things are done.
It is clearly from the females in the play that lead to the eventual happenings.