An origins theory is a theory that explains where or how something began.
Origin of the universe
The two major competing theories of the origin of the universe are creation ex nihilo, and the Big Bang. In addition, some people believe the universe has always existed, and therefore has no "origin" at all.
Origin of life
The two primary views on the origin of life are creationism and abiogenesis. Creationism holds that life was deliberately designed in a number of different forms which are unrelated to each other, and that these life forms were designed and created with the capacity to reproduce and vary somewhat in order to adapt to their environment. Abiogenesis is the concept that life could occur by natural forces working with precursor chemicals. Evolution holds that all life evolved from a single, simple lifeform through the process of variation and selection.
Issues surrounding the origin of life
The primary point of disagreement over the origin of life is whether or not all life is related (universal common ancestry), and whether or not variation and natural selection account for all diversity in life. Creationists argue that there is insufficient evidence of common ancestry to justify belief in it, and argue that many attributes of life are too complex or irreducibly complex to have evolved. Thus they do not dispute that some lifeforms are related or that some microevolution occurs. They only deny that all adaptive diversity in life can be explained through evolution alone. Evolutionists argue that there is sufficient evidence of common ancestry to justify belief, and that life is not too complex to have evolved.
- the Ancient astronaut theory has little credit