Not long ago, our ancestors lived in caves. But there is one cave in particular that we want your help locating for the Geo Quiz. It is called Wonderwerk Cave and archaeologists have found in it evidence of how and when early humans used fire. Scientists say it looks like our ancestors cooked food in the cave a million years ago. The cave is in South Africa and is the largest and most sparsely populated province in the country. It has got a long Atlantic coastline and is nestled in the Kuruman Hills. Northern Cape province is the answer to the Geo Quiz. It is where archaeologists have made a discovery about the early use of fire and the discovery is helping scientists better understand what role cooking may have played in human evolution. It is well known that our ancestors used fire to ward off predators, provide warmth, and cook food. But exactly when they started doing this is a matter of debate. A new study by an international team of scientists provides strong evidence that humans were using fire as far back as a million years ago. And that finding supports a provocative theory about the role cooking may have played in human evolution. The theory was proposed by Richard Wrangham, an anthropologist at Harvard University. He's the author of the 2009 book, "Catching Fire: How Cooking Made us Human". Wrangham says fire and cooked food shaped not just human culture, but human bodies. Take for exampIe, the size of the human gut. "Our intestines are simply about two thirds or less of the size that they would be in a great ape." He says we evolved smaller guts than other apes because we digest cooked food, which takes less work than digesting raw food. We also have smaller teeth than our primate cousins. "Because small teeth are associated with soft food, and cooking softens food," says Wrangham. He believes cooking also gave us the calories to evolve bigger brains. Wrangham contends these changes occurred well before modern humans, or Homo sapiens came into the picture. He argues an early human ancestor, Homo erectus was already using fire to cook food. The species first evolved nearly two million years ago. But strong archaeological evidence of the use of fire went back only 400,000 years. Until now, that is. The new study published on Monday in the Proceedings of the National Academy of Sciences suggests that fire may indeed have been used by our ancestor, Homo erectus. The evidence comes from million year old remains in Wonderwerk cave in South Africa. Study author, Francesco Berna of Boston University holds up small plastic bags containing fragments of animal bones found in the cave. "Here you have the bones, 1 million years old bones, that are gray because of the heat (of a fire)," says Berna. Berna confirmed that the bones were burned by using a technique called Infra Red Spectroscopy. "Because with Infra Red spectroscopy, the transformation of bone mineral that occurs when it is heated above generally 400-500 degrees, shows up very well, and unequivocally," he says. Berna also found evidence of heating in the sediments in that part of the cave. Berna's colleague, Paul Goldberg, also at Boston University further scrutinized the sediments in the cave using a special microscope. Goldberg sticks a slide under the microscope, and shows me what they found. "What you'll see is white patches of stuff, which are pieces of the ashes," he says. Goldberg doesn't believe that the ashes came from a wildfire, because they were too deep inside the cave. The ashes and bones were also associated with stone tools. And these were all found through several vertical layers, suggesting repeated fires. Now, the results don't prove that our ancestors were cooking their food a million years ago. After all, they could have dumped the bones in the fire after eating raw meat. But, Harvard University's Richard Wrangham says the study does offer the first conclusive evidence that human ancestors were controlling fire back then. "For me, that is very significant because once you control fire, I think it would be only a very short time before cooking became regular practice." Wrangham says the study also shows the value of this kind of microscopic analysis to find evidence of ancient fires. He hopes scientists will use the technique at other sites where early humans were known to live.