What makes us human? Some say that it is the development of language, though others argue that animals have language as well. Some say that it is our ability to use tools, though many animals are able to use rocks and other objects as primitive tools. Some say that it is our ability to see death coming. Now, researchers believe that they have found the definitive difference between humans and other primates, and they think that the difference all comes down to a single gene. Researchers from the University of Edinburgh in Scotland attribute the split of humanity from apes...