There are at least three possible approaches to the study of life's origins. A religious (i.e., non-scientific) approach would likely postulate that life was created by a supernatural being. Different religious traditions differ as to the details of this event, but since the process is supernatural it cannot, by definition, be studied scientifically. Nevertheless, intelligent design creationists often claim that we can identify those aspects of life that could not possibly have been produced by natural processes, by which they mean various evolutionary and molecular mechanisms (we will discuss these processes throughout the book, and more specifically in the next chapter). It is important to consider whether these claims would, if true, force us to abandon a scientific approach to the world around us in general, and the origin and evolution of life in particular. Given the previously noted interconnectedness of the sciences, one might well ask whether a supernatural biology would not also call into question the validity of all scientific disciplines. For example the dating of fossils is based on geological and astrophysical (cosmological) evidence for the age of the Earth and the Universe, which themselves are based on physical and chemical observations and principles. A non-scientific biology would be incompatible with a scientific physics and chemistry. The lesson of history, however, is different. Predictions as to what is beyond the ability of science to explain have routinely been demonstrated by to be wrong, often only a few years after such predictions were made! This speak to the power of science and the technologies based on science; for example, would an intelligent design creationist try to synthesize human proteins in bacteria?
Another type of explanation for the appearance of life on Earth, termed panspermia, assumes that advanced aliens brought (or left) life on Earth. Perhaps we owe our origins to casually discarded litter from these alien visitors. Unfortunately, the principles of general relativity, one of the best confirmed of all scientific theories, limit the speed of travel and given the size of the Universe, travelers from beyond the solar system seem unlikely, if not totally impossible. More to the point panspermia postpones but does not answer the question of how life began. Our alien visitors must have come from somewhere and panspermia does not explain where they came from. Given our current models for the history of the Universe and the Earth, understanding the origin of alien life is really no simpler than understanding the origin of life on Earth. On the other hand, if there is life on other planets or the moons in our solar system, and we can retrieve and analyze it, it would be extremely informative, particularly if it were found that this extra-terrestrial life originated independently from life on earth (rather than being transferred from Earth through various astronomical impact events).39