Aliens may be living among us, but we do not know it because they are microbes that do not have the standard biochemistry of Earth-dwelling organisms.
As well as the many forms of life based on DNA that are known to science, the Earth may have been home to a second creation of organisms that make up an unremarked realm of “life as we don’t know it”, according to Paul Davies, of Arizona State University, a cosmologist and theorist of extraterrestrial life.
Such “weird life” would never have been identified by scientists because the techniques they use for studying microbes are based on the familiar biological processes that drive the living things we understand, Professor Davies told the American Association for the Advancement of Science conference in Chicago.
The identification of such life on Earth could aid efforts to find life on Mars or elsewhere in the solar system. A second terrestrial creation would also indicate that life arises easily when the conditions are right, suggesting that it is common throughout the Universe...