How can you prove mermaids aren't real?

Answer 1

This runs into the problem of trying to prove something doesn't exist. The only way to prove a negative statement like this is to do an exhaustive search of the universe and this is obviously unfeasible. Same thing goes for "How do you know God doesn't exist".

However, there is compelling evidence for their nonexistence. All "evidence" of mermaids has been found either to be misinterpretation of normal creatures and phenomena, or deliberately faked. Additionally, looking at the course of evolutionary history it would be impossible for a creature to be half human and half fish.

Yes. I know the history of where they are from. They come from stories/myths of the ancient Celts to explain events they didn't understand. Mermaids do not exist and are make Believe.