@ Write4U and anyone else interested. The Stanford Encyclopedia of Philosophy constitutes a wonderfully informative and reliable source on any number of issues. Bookmark it! I quote below from its entry on
fitness:
The leading idea of Darwin’s theory of natural selection is often expressed in terms first coined by Herbert Spencer as the claim that among competing organisms the fittest survive (1864, 144). If there is random variation among the traits of organisms, and if some variant traits fortuitously confer advantages on the organisms that bear them, i.e., enhance their fitness, then those organisms will live to have more offspring, which in turn will bear the advantageous traits. Whence descent with adaptive modification, i.e., evolution. Evolution by random heritable variation and natural selection will explain ever increasing adaptation to given environments, increasing diversity in the occupation of new environments, and the complexity of organisms and their parts as their lineages adapt to one another and to their environments.
But what is fitness and how can one tell when a trait enhances fitness, or more to the point, when one organism is fitter than another? Opponents of the theory of natural selection have long claimed that the theory is so treated by its proponents as to define fitness in terms of rates of reproduction, thus condemning the principle of the survival of the fittest to triviality: the claim that those organisms with higher rates of reproduction leave more offspring is an empty, unfalsifiable tautology bereft of explanatory power. In the century and a half since the publication of On the Origin of Species biologists have all too often reinforced this objection by actually so defining fitness. For example, C.H. Waddington writes, in Towards a Theoretical Biology (1968, 19), that the fittest individuals are those that are “most effective in leaving gametes to the next generation.” It appears therefore that evolutionary theory requires a definition of fitness that will protect it from the charges of tautology, triviality, unfalsifiabilty, and consequent explanatory infirmity. If no such definition is in fact forthcoming, then what is required by the theory’s adherents is an alternative account of its structure and content or its role in the research program of biology.
In a nutshell, then: If the theory of natural selection is to be a respectable, empirical scientific theory with all the attributes that we expect of a good theory (predictive power, explanatory power, etc.) then inter-related terms such as
fitness,
adaptation, etc. must be defined in such a way that they make no reference whatsoever to survival and reproductive success.
No one, to my knowledge at least, has ever been able to do this, and I have grave doubts that it
can be done at all.
Until that day, assuming if it comes at all, the theory of natural selection -- deceptive appearances of being solid science to the contrary notwithstanding -- remains on a par quite literally with other tautologies such as "dogs are dogs", explaining nothing, predicting nothing, and serving no useful function whatsoever.
"But, but, it's so
simple" Pinball protests "Even a child could understand it".
I respond: It's all so simple to convince yourself you have understood something when, in fact, you have understood nothing at all.
"But, but . . . " the protests continue "How could top rate scientists such as Charles Darwin and a thousand followers not be
aware of this?" "It's just not possible that intelligent scientists galore failed to see that their theory amounts to an empty nothingness on a par with
dogs are dogs. C'mon now! Who are you trying to kid?"
First of all, plenty of thinkers
have been aware of the problem. Some, including philosophers and scientists themselves have offered solutions. None are satisfactory. The vast majority of scientists, I daresay, have just never even thought about it, or if they did, dismissed it as preposterous.
Second of all, some tautologies are more obvious than others. The empirical vacuity of "
Dogs are dogs" is immediately apparent to all. It might take you a bit longer to see that "
All ancestors produce offspring" is equally empty of empirical content. And it might take you a lifetime to recognize and understand the empirically vacuous truth of a complex mathematical proof -- Fermat's last theorem, say.