String Theory is at present untestable, so it's just a path of scientific inquiry. However asking the question of why we are here is really asking the question of why is there LIFE.
In 1970 the Russian Mathematician Yuri Matiyesevic proved the unsolvability of Hilbert's 10th problem. His proof followed an argument that could be summarized in a finite combinatorial process, which eventually gives rise to an infinite process exceeding an exponential (continuous) process. This idea followed from using the Fibonacci sequence, which starts with two objects and gives rise to a third. Now Fibonacci sequences have been observed in a significant number of living things. Leading one to believe that a simple Trinity of objects gives rise to all others.
Ramsey's Theorem (1926) says that there is no such thing as complete chaos (i.e. no complete universal entropy and hence no structure, and hence no observance of change and time passage is possible) and that order must evolve eventually.
The Li-Yorke Theorem (1978) says period three implies all other periods (chaos). Now Man is the highest ordered living complexity that we know of. Is it possible that the seeds of LIFE were planted in some way evidenced by a combination of these three (and possibly more) discovered Mathematical Theorems? Is it possible that String Theory is evidenced by the very existence of humankind, and no further inquiry is needed?