'You can't define "fittest" in any testable, concrete way... at best you have a tautology: "the fittest" = "those who survive long enough to reproduce the most" ... therefore we just have a single, self-evident statement-- not something testable or falsifiable.'
No. Fittest means how many (viable) offspring one individual will create, so it is a quantifiable trait. I do not understand where you get this equation from.
The equation is:
-> The more viable offspring = the fitter one is.
Not vice versa. It is a simple manner of counting, nothing more.
As long as no offspring were created, the fitness will be 0. (The offspring need to be viable, because otherwise they could not reproduce and thus could not on their own create offspring, so one needs to look if they can create offspring too. It would mean the end of a given species if their fitness would become 0. When the dinosaur became extinct, for whatever reasons that happened, their fitness became 0 as well. It is that simple, but it is also a concept which does not EXPLAIN a whole lot).
If a guinea pig has 0 offspring, the fitness is 0 too, and thus it is "not fit". But you would need to analyze why it is not fit. For example, a guinea pig in a cage normally has a real fitness of 0, because it will probably not be allowed to mate. Or take poisoning in the food chain as an example, i.e. biomagnification
of DDT in indian vultures's eating sheep, or estrogen hormone levels in ponds affecting frogs or humans.
The term fitness applies to reproduction.
However, with that beind said, the term
"natural selection"
is even more problematic than fitness, because natural selection is just a lazy word for describing MANY different things altogether. I dont like this term. There is nothing "natural" about it, it just happens because of many DIFFERENT reasons.
And "Selection" is also not really important, because as long as either some offspring survive and reproduce, or there are other mates in your population, it hardly matters.
As a concept, "natural selection" does not explain a lot. Only "intelligent design" or "life-arrived-from-outside-planet-earth" are more annoying. Both explain 0. They just state something which you can never verify. (Although I believe at some later point we can proof how "life" emerged. My theory is that the molecular machinery came into existance in the deep sea with Ribosomes that folded inside of liposomes using some cationic metal factors ... maybe sulphuryl-bonds. Chemistry will be able to answer that more accurately, after all life is nothing than a few genes and enzymes in a compound called a cell capable of setting together ATP and nucleotides)
What would be a LOT better as a concept would be co-evolution. This way you could exactly describe why certain birds have such a beak, and certain others a different beak.
