Mutations are: the source for all variation within groups, occurring when DNA is replicated erroneously. a science-fiction term used in popular culture (e.g., X-Men) to describe how the human race might continue evolving. witnessed only in cases involving radiation, exposure to certain chemicals, and viruses, and have wholly negative consequences such as disease and death. only positive alterations to our DNA, enabling evolution to favor traits such as bipedalism and larger brains.