Characterization
Throughout the course of the series, Brennan appears to be a straightforward, brilliant anthropologist, who lacks social skills. Her social ineptitude is especially apparent when it comes to sarcasm, metaphors which she often interprets literally, and pop culture jokes. An example of this is when she mistakes Colin Farrell for Will Ferrell.
She had a difficult adolescence, and it is implied that her withdrawn social tendencies are a defense mechanism. She also sometimes struggles in identifying and explaining her emotions, and takes comfort in the rationality of her anthropological discipline. Although it has been stated that Brennan was based on a person with Asperger syndrome, this has never been confirmed in the plot of the series. The creator of the series has stated that the character was never labeled as having the syndrome in order to increase the appeal of the show on network television. This influence on her character also helps to explain her extreme rationality in early seasons, as well as some of her social difficulties. Brennan is a self-proclaimed atheist and often points out what she believes to be the irrationality of religious and spiritual beliefs. This has led to more than one argument with Booth, who is a devout Roman Catholic; he becomes particularly irate when she compares less common religions, such as voodoo, to Christianity.
Brennan is a bestselling author, who has been on the New York Times Best Seller List for 18 weeks. She is trained in three types of martial arts, has hunting licenses in four states, and has a legally registered gun as well as a diving certificate. She promised to consider becoming a vegetarian after seeing how pigs were slaughtered (which was also the way her mother had been killed). However, in "The Tough Man in the Tender Chicken" (season 5, episode 6) Angela cites health reasons for Brennan's vegetarian diet. Brennan is also a trained amateur highwire performer, and speaks at least seven other languages, including Spanish, French, Latin, Chinese, Japanese, Norwegian (although she says only "skull" and avers that, as a forensic anthropologist, this is a word she knows "in just about every language"), and German. She has also admitted to knowing a bit of Russian. She often says she does not "put much stock in psychology" and makes a point of noting that Dr. Sweets is not a real scientist as he "bases his life on the vagary of psychology and emotions".
Brennan's personality undergoes significant changes throughout the course of the series. Her thinking becomes less rigid in later seasons, something which is observed by Dr. Gordon Wyatt, who notes that she is now able to distinguish the difference between accuracy and truth. In season 4, Booth takes her along to his interrogations and helps her learn how to set aside her scientific perspective and relate with the victim's family. She is also able to put aside her rationality to support her friends in sometimes irrational pursuits, such as Angela's quest to raise money to save a pig from slaughter. Her sensitivity and empathy towards others are also much improved, seen quite strongly when she comforts Booth's grandfather, and when she attends a funeral so that the victim's mother won't be alone. She also displays more "typical" human emotions when in extreme stress. One example of this is her fear of snakes in "The Mummy in the Maze," when a girl is in the process of being scared to death in a room, the floor teeming with snakes. This goes against her empirical nature, as, when Booth tells her that the snakes aren't venomous, she states that she is aware, but will not step in the room, causing Booth to carry her on his back.
Brennan begins to feel both dissatisfaction and discomfort with her work toward the end of the fifth season. She also sees some futility in her work, stating that no matter how many killers they catch, there will always be more. To help her gain new perspective, she later decides to head up an anthropological expedition to Indonesia for a year to identify some ancient proto-human remains, after mulling it over during the episode. However, 7 months later, she and everyone else return to D.C. in order to save Cam's job, and they all decide to stay.
As season 6 progresses, Brennan must confront her feelings for Booth, whom she rejected in the 100th episode from the previous season. Having returned from 7 months of introspection, she has come to terms with her romantic affection towards him, even admitting that she regretted not having given them a chance together, mid-way through the season. However, Booth returns from Afghanistan with a new love interest, war correspondent Hannah Burley, whom Brennan befriends. When Hannah rejects Booth's marriage proposal, Brennan must help him through the emotional fallout.
In the second to last episode of season 6 Booth and Brennan had sex, consummating their relationship, and it is revealed in the last few moments of the season finale that as a result, Brennan has become pregnant, with Booth the father. Throughout the episode ("The Change in the Game") Brennan has been seen asking Angela questions and making comments that make her seem excited and apprehensive; when she sees that Booth is happy with the news, she also seems overjoyed. This reflects her earlier desire to become a mother, circa season 4, as well as her desire that Booth be the father of the baby.
In the Season 7 finale, Brennan shows further development when she allows Christine to be baptized, despite her stance as an atheist, because Booth thinks it's important.
In the Season 8 episode "The Shot in the Dark", Brennan is shot while working in the lab late at night. While undergoing emergency surgery, she experiences a vision of meeting with her deceased mother, Christine Brennan. Initially dismissing this as a hallucination, Brennan experiences several more visions throughout the episode. During these discussions, it's revealed that Brennan's hyper rationalization originates from the very last piece of advice her mother gave to her (before going on the run) which was to use her brain instead of her heart. While that advice enabled Brennan to survive all these years, the vision of her mother explains, it's now time for Brennan to do more than just survive.
Read more about this topic: Temperance "Bones" Brennan