Until 1697, when *Cygnus atratus* was discovered, no one thought black swans could exist. (photo [Holger Detje](https://cdn.hashnode.com/res/hashnode/image/upload/v1614109136294/cPHLvSBoJ.html) from [Pixabay](https://pixabay.com/?utm_source=link-attribution&utm_medium=referral&utm_campaign=image&utm_content=122983))