The theory publicized in 1997 in the pseudohistorical book The Templar Revelation by Lynn Picknett and Clive Prince, that the person to the left of Jesus (to his right) is actually Mary Magdalene, rather than the apostle John (as most art historians identify the figure). This theory was central to Dan Brown's popular 2003 novel The Da Vinci Code. In the novel, it is said that John/Mary Magdalene has a womanly bosom, feminine facial features, and is swaying gracefully toward Peter. Peter appears to be making a threatening gesture across John/Mary's throat. The author uses this theory to advance his view that Leonardo da Vinci was once the head of a secret society, the Priory of Sion, which protects the secret of Jesus' royal bloodline, and the location of his modern descendants.The fact is, however, that while damage makes it impossible to be sure of the figure's gender, it appears to be wearing male clothing. Although Mary could have been wearing male clothes, it is not highly probable. There are only 13 figures in the painting, so if one is Mary Magdalene, an apostle is missing: somebody would have noted a missing male apostle earlier. Some have suggested that on the front of the figure of Simon Peter there is one hand with a dagger which is associated to nobody in the picture, but in clearer reproductions this is seen to be Peter's right hand, resting against his hip with the palm turned outward; the knife points towards Bartholomew (far left) who was to be executed by being flayed. It may also indicate Peter's impulsive nature, as he cuts off a soldier's ear in John 18:10. A detailed preliminary drawing of the arm exists. Other paintings from that period (Castagno's 1447 and Ghirlandaio's 1480) also show John to be a very boyish or feminine looking figure with long fair hair. This was because John was supposed to have been the youngest and most unquestioningly devoted of the apostles. Hence he is often shown asleep against Jesus's shoulder. It was common in the period to show neophytes as very young or even feminine figures, as a way of showing their inferior position. This tradition continued well after the period, as the 19th century sculpture in Drogheda Cathedral, Ireland demonstrates. Not to mention that Leonardo also portrayed a male saint with similar effeminate features in his painting St. John the Baptist.
Leonardo da Vinci has been extensively investigated by Sigmund Freud. He took particular pleasure in this investigation, because he saw it as a stage in psychoanalysis's conquest of culture. "Biography, too, must become ours," he wrote to Jung on October 17, 1909, and added that "the riddle of Leonardo da Vinci's character has suddenly become transparent to me. That, then, would be the first step in biography." He took pleasure in writing about him, too, because he greatly admired Leonardo as one "among the greatest of the human race." Yet this admiration did not exempt Leonardo from psychoanalytic scrutinity. "There is no one so great," Freud wrote, "as to be disgraced by being subject to the laws which govern both normal and pathological activity with equal cogency." There were other, hidden, aspects to Freud's preoccupation with Leonardo: his study of this artist, whose homosexual inclinations he considered proved, came at a time when he was analyzing the residues of his own feelings for his former intimate friend Wilhelm Fliess. In any event, quite apart from this autobiographical source of Freud's interest in Leonardo's "case," his discussion of one way to homosexual object-choice remains of great interest.
And here it is an article on the connection between Freud's cocaine habit and his homosexual tendencies:http://www.historyhouse.com/in_history/cocaine