The "Mad Men" actress, who plays Don Draper's sullen ex-wife Betty, gave birth to son Xander Dane Jones in September 2011, but never said who the father was, squarely placing the boy's paternity in the Ministry's Department of Mysterious Mysteries. Speculation included her ex Jason Sudeikis, her "X-Men: First Class" director Matthew Vaughn and a sperm donor. Others joked it was a "virgin" birth. And lately the actress has been linked to just about every male she can fit in a photographer's frame with, including Miley Cyrus' fiance, Liam Hemsworth. But Jones remains tight-lipped on the subject of her son's father and seems to want to keep it that way. "That's my son's business," the 35-year-old recently told the New York Times. It's not the public's business. Jones' real-life character has become homogenized in the media with her icy "Mad Men" persona because she reveals very little about her inner workings. Jack Nicholson once told me: 'You should never give your personal life away. Otherwise, people will pick you apart. They'll never believe in your character' " she added. The "Sweetwater" actress is consistently guarded but can be self-mocking, the paper said, despite her humorless-seeming persona. "Women should have lots of secrets," she said. It's our right to have secrets. Otherwise, what would we write in our memoirs? Jones, whose bold fashion choices commonly land her on best and worst dressed lists, still knows how to make headlines, such as when word came that she ate the placenta after her son's birth to stave off postpartum depression. "It was like taking a vitamin blended into a smoothie," she said, sarcastically adding, "I'm a mammal. I nursed. I did all kinds of weird stuff. After something like that, does anyone really want to know much more?