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"they" refers to anyone who uses Billions of years to jump from a theory of how it was to how we observe something is today... As for how it is relevant, I feel that question and statements I posed is at the heart of this article, the assumption of evolution.

There is no doubt in the fundamental foundations of reality that evolution is a thing =/

If you don't trust 'them', you are, like anybody else, absolutely free to 'question everything' and do the experiments yourself. But I can speed up the process and tell you you'll end up with the same results