We are the only species on earth that cooks its food - and we are also the cleverest species on the planet. The question is: do we cook because we're clever and imaginative, or are we clever and imaginative because our ancestors discovered cooking? Horizon examines the evidence that our ancestors' changing diet and their mastery of fire prompted anatomical and neurological changes that resulted in taking us out of the trees and into the kitchen.

Odds are excellent that extraterrestrial life exists. So why haven’t we found aliens out in the galaxy? Are we looking in the wrong places? New research shows we should look closer to home, even inside our bodies. It turns out that a lot of our DNA is from a mysterious, nonhuman source. Theoretically, alien microbial life can make the journey to Earth from distant worlds, and scientists are finding some unearthly microbes in our upper atmosphere. Could it be from outer space? Could we be part alien? It’s even possible alien life is already here as digital life forms, hiding inside our technology.

Austrian director Michael Glawogger travels to five countries to focus on some of the worst jobs imaginable: Ukrainian miners crawl into tiny cracks in old coal pits to scratch out a few bags of winter fuel; Indonesian workers trudge long distances carrying baskets with hundreds of pounds of sulfur chunks extracted from a steaming mountain; Pakistanis risk explosions and burial under tons of scrap iron as they dismantle huge carrier ships. The visuals are everything here. Despite the hardships depicted, many sequences have a dreamlike beauty. In addition, the director has a bone-dry sense of irony; during the Ukraine scenes, he frequently cuts away to a statue of Stakhanov, the "hero" lauded by the Soviets for his superhuman work habits. He also shows us an old German smelting works that's been converted into a theme park.

Of the four elements, air is the most elusive because we can't see it. There's something very magical about it. One of the ways we transform food is by getting air into it. Think of the soufflé, think of the loaf of bread. These things are elevated by the fact that they now contain air. They're ethereal. Visit food labs and Moroccan fields as Michael Pollan delves into the science of bread-making and the nature of gluten.

Boxing, 'the poor man's sport', has long given kids from America's roughest neighborhoods an opportunity to escape violence with violence. But with success in the ring comes new fights for which there is no training: champions are made and broken in the blink of an eye, and young men thrust into the spotlight are often ill-equipped for the fame, fortune, and hangers-on that accompany a title belt". And for many, the toughest bouts are fought during retirement, when health and financial issues begin to mount. Built around the stories of heavyweight legends as Mike Tyson, Evander Holyfield and Bernard Hopkins, We will examine their lives in and out of the ring.

From unexplained flashes in the night sky to flying saucers, this episode delves into the mysterious world of UFOs. How our drive to explain these bizarre phenomena, and desire to discover little green men, has in fact transformed our understanding of the universe