That not how statistics work.

If humans would not exist, you would not be writing this post in the first place.

In other words. You are mixing prior probability with posterior probability. Prior probability of 'us existing' might be astronomically small (or not - we don't know), but in a world in which you already exist that probability is 100%. And knowing posterior probability gives you zero information on prior probability in this case.

P(humans_exist) != P(humans_exist | you_exist) and you only can measure the P(humans_exist | you_exist) part which equals 100%.