Historically how has the origin of life on earth been explained?
The mainly recurrent explanation for the phenomenon of life on earth is the mythological. The People from various parts of the world developed explanatory myths about the origin of animals and human beings. Few of those myths were incorporated into religions and almost all religions have metaphorical or transcendental explanations about the origin of life on the planet and with the development of science new explanatory attempts have emerged.
The prominent among them are the spontaneous generation abiogenesis or hypothesis that asserted that living beings were created from nonliving material, the cosmic panspermia hypothesis, theory that life on earth is a result of seeding from the outer space, the autotrophic hypothesis, according to which the first living beings were autotrophs, and the heterotrophic hypothesis, the most accepted nowadays, that affirms that life emerged from heterotrophic cells.
Latterly of the 1980s decade a new hypothesis called as the RNA world hypothesis was presented. This hypothesis asserts that the primitive life had only RNA as genetic material and as structural molecules that later turned into DNA and proteins. The RNA world hypothesis is the strengthened by the fact that RNA can play a catalytic role, like enzymes, and by the finding that some bacteria have ribosomes made only of the RNA without associated proteins.