If the theory of evolution is true, then how did the first creatures get on earth?

In contrast to the first poster, I will actually try to answer the question, which is not a question about whether evolution is true, but rather is doing a thought experiment and presuming its truth in order possibly to result in a contradiction that might disprove it, which is a perfectly valid and scientifically sound way to proceed. First, just quickly to respond to the other poster, there is a lot of evidence for evolution. More than enough to establish its truth (and it's easy to find books that lay out the evidence for the layperson, and you can go to the museums and see the fossil records for yourself). Clearly, scientists also use reason in order to extrapolate from the evidence to the best theory that explains all the evidence. Given, for example, that bats and birds share a bone structure in the wings that is hard to explain by chance even though they are distant relatives genetically, the best scientific explanation is one that explains the similarity in terms of similar needs to adapt to flight in order for each particular species to successfully propagate. Fossil records when recovered in a biostratigraphically sound way, allow scientists to note a historical development, again pointing to evolution as the explanation that makes the most sense and requires the fewest unnecessary assumptions (Ockham's Razor). I agree that academicians like bureaucrats sometimes exclude heterodox thought because it threatens the entrenched establishment. This I believe has happened with evolution as in nearly every other academic field, whether in the sciences or the humanities. There is, however, no evidence at all that evolution itself was "invented" as a hoax to keep evolutionists in power. The poster him/herself grossly disregards the very scientific method touted at the top of the post. To get to your question, it is true that no one has sat and observed evolution taking place. There is an obvious reason for this. Evolution occurs over spans of time greater than a human life or the life of any other single organism (by definition, really--that's what evolution means: the adaptation over many, many generations of organisms (not an organism) to their environment (in other words, the "origin of species" as Darwin termed it). To say that we can't observe something direclty, therefore science must remain silent, would be to exclude most of what anyone intuitively would consider sound knowledge. According to that view, no one should believe that anyone ever lived on Earth before the present generation and anyone in previous generations that one has actually seen alive. (I'm getting to your question, trust me). The objection would be, but we have evidence that they existed and the best explanation is that they did. That's exactly the case with evolution: there is evidence and the best explanation to account for it is the theory of evolution, just like we have a theory that other human beings existed before we did even if we never saw them alive, because to deny it would be absurd. As to the origin of of the first creatures, be careful, you're "begging the question" a little bit by using the term "get", i.e. you're assuming that whatever accounts for the origin of life it involves creatures "getting" to the Earth, which sounds like they must have come from somewhere else. There is as of now no definitive and widely accepted account of how life on Earth first originated, as in the creation of the first cell able to replicate itself in some form. The problem with finding evidence to support a theory of the origin of life (in contrast to a theory of evolution) is that the process itself did not replicate itself but only the result of that process, i.e. the actual first organisms. If I baked someone a cake and they asked me how I did it, I could show them the cake and I could reproduce the procedure, but I wouldn't be able to reproduce the procedure for that particular cake; I would have to use similar ingredients to show them. Scientists are now fairly certain what inorganic components went into the origin of life (carbon-containing amino acids and nucleic acids) but unlike with the cake, we don't have a recipe or blueprint for turning the components of life into self-replicating organisms. Scientists are still experimenting and trying to replicate this process in a laboratory. But keep in mind, it was a one-time event and science has so far been unsuccessful in giving a definitive and widely-accepted theory. This by no means impugns the validity of the theory of evolution as a process, since this theory starts with the first replicating cell and gives an account of the development of that cell over billions of years into various species. Evolution in its widely accepted form does not claim to be able to account for how life originated (we would have to change its name to something broader, if it did). There are currently different possibilities that scientists are investigating: from comparing the conditions in which thermophiles in the ocean are able to replicate at extremely high temperatures to early (first .5 to 1 billion years) conditions on the Earth to varying degrees of the panspermia hypothesis (that the first single-cell microorganisms were ones that could withstand the conditions of interstellar space and arrived on Earth on meteorites). The question is an extremely difficult one to investigate, but none of the possibilities that would be compatible with the overwhelming evidence for evolution (e.g. even panspermia or even for that matter a spiritual being who placed the first single celled organism on earth) are incompatible with the theory of evolution, which is, again, a theory of the development and not the origin of single-cell organisms on Earth over billions of years into the variety of species we observe today.