Yet extinct species are "proven to not exist" by being "not proven to exist/proven to not exist" according to the sciences of biology and ecology.QFT
"Not proven to exist" =/= "proven to not exist".
Just say "I don't see a chair" and stop pretending that science is on your side when you say the chair doesn't exist.
How do you know if you hold a jellybean in your hand? How do you know if you don't?
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