Eat Up: Eating a large meal at the holidays won't have a big impact on your weight, says one physiologist. That's because your brain keeps a close watch on food intake and can tolerate the occasional big meal. It's slow, steady weight gain that's more problematic. iStockphoto.com hide caption

itoggle caption iStockphoto.com

Four of the seven lion cubs (Panthera leo) recently born at the National Zoo in Washington, D.C. Lions boast a special form of sister and brotherly alliance: sisters stay together all their lives in prides, and brothers form coalitions to conquer other prides. Mehgan Murphy/Smithsonian Institution hide caption

itoggle caption Mehgan Murphy/Smithsonian Institution

Lou Gehrig smacks a homer in a game between Major League stars and a Japanese all-star team. Hulton Archive/Hulton Archive/Getty Images hide caption

itoggle caption Hulton Archive/Hulton Archive/Getty Images

Songbirds, like this male tricolored blackbird, develop regional accents in the same way humans do, researchers found. And, like humans, songbirds seem to respond better to accents they already know. Dave Menke/Courtesy of the U.S. Fish and Wildlife Service hide caption

itoggle caption Dave Menke/Courtesy of the U.S. Fish and Wildlife Service

This sculpture of a Homo neanderthalensis adult male represents Neanderthals that lived between 225,000 and 28,000 years ago. It is a reconstruction based on Shanidar 1, made for the Smithsonian Human Origins Initiative. John Gurche, sculptor, Chip Clark, photographer/Smithsonian Human Origins Initiative hide caption

itoggle caption John Gurche, sculptor, Chip Clark, photographer/Smithsonian Human Origins Initiative

An AquAdvantage genetically engineered salmon behind a non-transgenic Atlantic salmon sibling of the same age. Courtesy of AquaBounty Technologies hide caption

itoggle caption Courtesy of AquaBounty Technologies