In the 14 billion year old Universe, humans have only existed for 200,000 years or so. That’s 1/70,000th of the Universe’s lifespan. There are 100 billion stars in our galaxy alone. If another species evolved along a similar trajectory as we have, but did so 10 million years ago, they could have already visited the Earth and we would have no idea. Life first emerged on Earth 4.5 billion years ago, leaving 9 billion years prior for life to evolve elsewhere and potentially even be brought here altogether.