Science reveals common sense to be fact! A study conducted by Dr. Bahman Guyuron and published in The Plastic and Reconstructive Surgery Journal researched the appearance of aging twins to determine why one half of the pair would be protected by time while the other would become wrinkled. While the side-by-side slide shows can be shocking, the reasons behind the wrinkles are exactly what your mama warned you about. Keep reading to find out how some of the twins stayed young-looking:

Last night in Switzerland, Roger Federer, the #1 tennis player in the world, became the proud father of not one, but two babies. His twins Myla Rose and Charlene Riva are another pair to add to the list of celebrity twins. It almost seems like an epidemic at this point. Celebrity gets pregnant, celebrity pops out twice the babies. Is it because celebs don’t naturally procreate and often opt to use in-vitro? Is it because celebs are just so gorgeous the world could use more of their good genes? Is it because in general the whole world is birthing more twins? Who knows!? Here’s a list of celebrities who have become parents to twin babies in the last few years.

Sarah Jessica Parker and Matthew Broderick have released their first family pic with newborn twin girls, Marion and Tabitha (who a surrogate popped out last Monday), alongside big brother James Wilkie. Looks like this family won’t be going the gender-neutral route—notice how the girls are in pink and the boys are in blue. [People]

Mia Washington of Dallas, Texas, gave birth to twins, but what she didn’t know was that an affair she had would be brought to light after the birth of her sons. Two of Washington’s eggs were fertilized by the sperm of two different men. After noticing that 11-month-old twins Justin and Jordan were developing different facial features, Washington and partner James Harrison decided the family should undergo DNA testing. Didn’t I see this on an episode of “All My Children”?

When we heard about a new procedure that can check a fertilized egg’s viability before it’s implanted, we thought there might be fewer multiple births in the future. Well, it’s not looking that way. Apparently women, especially career-oriented ones, are hoping more than one egg will take when they get in vitro, so they can get more than one pregnancy and child birth over with at the same time. An article in Page Six Magazine this weekend included interviews with mothers who happily gave birth to twins. After the jump, a few of our favorite quotes from ladies who loved getting “two for the price of one.”

Everywhere I turn, there’s a new set of twins, with four big boobs, two heightened libidos, and a camera. 2008 was all about two things: bisexuality and twins. Tila Tequila made a name for herself as a bisexual woman looking for love, while Lindsay Lohan came out and met the Ronson of her dreams. And everyone had twins this year—Brangelina, J. Lo, Nancy Grace, the list goes on. But in 2009, being bisexual and having twins isn’t going to get headlines—to be a STAR, you’ll need to be BOTH. Hugh Hefner just added two new Playmates to his mansion—twins Kristina and Karissa Shannon. This scenario makes my brain and my tummy hurt, because I can’t help but wonder if they get it on with Hef TOGETHER. Likewise, the new season of “A Shot At Love” is actually a “Double Shot” and features the “Ikki” twins, Rikki and Vikki, who are trying to find a perfect match amongst a pool of sexy beefcakes and hot lesbians. Meanwhile, at New York club The Box, the hottest featured act is the Porcelain TwinZ, who put on a fetish-burlesque show. What’s next? Mary-Kate and Ashley doing porn? “Sweet Valley High” erotica?

Today marks the 20th anniversary of the release of “Dead Ringers”—the mega-awesomely creepy David Cronenberg movie which made us vow never to date identical twin gynecologists after we rented it on VHS one rainy day at Blockbuster.  Starring a dashingly young Jeremy Irons as brothers Eliot and Beverly Mantle—who look so identical that they routinely swap girlfriends without telling them that they’re, um, two people—“Dead Ringers” is chock full of hot love and heavy psycho-drama.  We’ve always loved the opening scene, which offers the handy-dandy lesson on human reproduction in the clip above. [Amazon and IMDB]

Rauhin, an eight-year-old panda who lives in Japan’s Adventure World, gave birth to twins this weekend! She is now the mother of a boy and a girl, and is the first panda born in captivity in Japan to successfully give birth. That fleshy thing she’s holding is one of her offspring. It will look much, much cuter once it gets fur.

We were positively puzzled when we saw this headline on Variety.com: “Jolie replaces Cruise in ‘Salt’.” According to the article, Angelina Jolie may take on the title role in Edwin A. Salt, a film about “a CIA officer who is accused by a defector of being a Russian sleeper spy and must elude capture long enough to establish her innocence.” Tom Cruise had wanted to play the role for a long time, but when his interest faded, and Jolie expressed her enthusiasm and the studio decided to rewrite the screenplay with a female lead (the title will also be changed). Now, we didn’t think Angelina and Tom had anything in common, except for the fact that they’re both half of high-powered Hollywood couples, but upon further inspection, we found that the two may have been separated at birth.

In the past few years, the following celebrities over the age of 35 have given birth to or are expecting twins: Marcia Cross, 44; Jillian Dempsey (wife of Patrick Dempsey), 40; Rebecca Romijn, 36; Jennifer Lopez, 38; Julia Roberts, 37; and Nancy Grace, 50. Angelina Jolie just gave birth to her twins at the age of 33, with Us Weekly claiming that she conceived via in-vitro fertilization (IVF)—a story she and Brad Pitt deny, saying they would have been happy to talk about using IVF, if that had been the case. Of the other women mentioned, none of them have only Marcia Cross has spoken out about using IVF to conceive, and a few others have outright denied it, despite the fact that a woman’s ability to conceive drops significantly after the age of 35.

Some stories are truly stranger than fiction. Darla and Mark Pritchard tried to have a baby for five years, but nothing was working, even after two in-vitro fertilization attempts. Then, Darla’s twin sister, Dana Johnson, offered to be a surrogate, and it seems that both Darla and Dana had Darla eggs (fertilized by Mark) implanted, and both became pregnant. Darla gave birth to twins, and six weeks later, Dana gave birth to a girl. Even though they came out of different women and don’t all have the same birth date, the three children are considered triplets. Even Darla and Dana seem a little confused when they try to talk about the ordeal in the above video. [CBS News]