In a sense, it's true that it's tautological, but only in that we often don't know for certain what was fit, or why. And we often can't. For Darwin's finches,

In a sense, it's true that it's tautological, but only in that we often don't know for certain what was fit, or why. And we often can't. For Darwin's finches, we can make a good guess, but some animal appearances or behaviors (e.g. the most beautiful snakes [1]) we just have to shake our heads. We know the snake's beauty (in our eyes) must have increased fitness since it was conserved, but how? [1] https://duckduckgo.com/?q=the+most+beautiful+snake&t=brave&iax=images&ia=images https://duckduckgo.com/?q=the+most+beautiful+snake&t=brave&i...