It's kind of obvious, isn't it. Some new feature becomes desirable.
Some animal A of a species will pass on their gene because they inhibit it.
Some animal B of a species will pass on their gene because they find A attractive.
The girl in your picture is also the quintessential example for people being into neotenous attributes
https://youtu.be/lSL8SuB6vFYso what's attractive can be more universal than any particular property. E.g. "being young" is recognizable in any animal, whether you have tentacles or walk on two legs.
