The scientific investigation is the systematic approach of the scientists to answer the questions about the world. It is applied almost all of the theories including the Theory of Natural Selection. Darwin's theory of evolution is a result of scientific investigation. In this theory, they investigate by observing the distribution of species.
tRNA-precursors were smaller than the modern tRNA and their primary function was to participate in the formation of new structures by joining two or more RNA molecules.
The adaptor hypothesis is the explanation of how information could be extracted from a nucleic acid into a string of amino acids in a specific sequence. The proposed explanation involved recognition between the adaptor (today tRNA) and the template nucleic acid .
All of these are dangers posed by introduced species