Is the 'law' of survival of the fittest a tautology?
The basis of the Darwinian Theory of Evolution is that the members of a population with the sets of characteristics which are most suitable for the local environment are the ones who are most likely to survive to have greater numbers of offspring. Thus those characteristics suited to the local environment will become more common in the population as a whole, over the generations, and characteristics that are not well suited to the local environment will disappear (or at least become rarer).
This idea is typically expressed by saying something like "only the fit survive" or simply that there is a rule of "survival of the fittest."
A tautology is a meaningless repetition of the same idea in different words. Some people argue that the 'law' of "survival of the fittest" which forms the basis of evolutionary processes is in fact a tautology, and therefore the theory of evolution itself is meaningless.
Here's one expression of the argument, taken from www.alternativescience.com
... Darwin's original conception of natural selection, or the survival of the fittest, is fatally flawed.
The problem is: how can biologists (or anyone else) tell what characteristics constitute the animal or plant's 'fitness' to survive? How can you tell which are the fit animals and plants?
The answer is that the only way to define the fit is by means of a post-hoc rationalisation -- the fit must be "those who survived". While the only way to characterise uniquely those who survive is as "the fit". The central proposition of the Darwinian argument turns out to be an empty tautology.
It it really reasonable to define fit as "those who survive"? Certainly if you use that definition then the statement "only the fit survive" or "survival of the fittest" becomes "only the survivors survive" or "survival of the survivors", a tautology.
But that doesn't make much sense when you think about it, does it? One wouldn't normally use the word "fit" to mean only that some person or animal had survived. "Fit" generally means better equipped to survive. That is, the faster running cheetah, for example, who is more capable of capturing prey, therefore more likely to live longer and have more offspring.
The question asked above is "how can you tell which are the fit animals". Well, if the fit animals tend to survive and have more offspring than the 'less fit' one way to tell which animals are fit is to look at the ones that had more offspring... those that survived. But doesn't that make the above author correct? Doesn't that mean that "fit" is defined as "survivor" and therefore Darwinian evolution is based on a meaningless tautology?
No, it does not. Looking at the set of survivors is one way to tell which animals are fit. However, the fact that the animals survived does not determine or define their fitness.
Consider a different law: "drinking of the thirsty." This 'law' states that thirsty people tend to drink more water. So, how can we determine who is thirsty?
Now consider this statement: The answer is that the only way to define the thirsty is by means of a post-hoc rationalization -- the thirsty must be those who drank.
That is certainly not the case. Being thirsty is a real condition which causes people to drink. Thus we can determine who is thirsty by looking at who drinks, but that does not mean that being thirsty simply means drinking. Similarly, being fit is a condition which tends to lead to higher survival rates, and thus larger numbers of offspring. Thus we can determine who is fit by looking at who survives, but this does not mean that being fit simply means surviving.
So what does "fit" mean? How can we tell independent of survival rates or number of offspring which animals are more fit and which are less fit? The answer is that it is next to impossible in practice. It seems reasonable at first glance to say things like "a cheetah that can run faster is more fit", but perhaps being able to run faster comes at a cost. Perhaps the cheetah's bones are too thin and likely to break. Perhaps the amount of extra energy the faster cheetah uses to capture a meal is out of proportion with the energy provided by extra meals caught because the animal is faster. Tradeoffs like that are one reason why cheetahs do not run at the speed of sound.
However, it is possible in principle to determine the fitness of an animal. One would have to be nearly omniscient in order to calculate all the tradeoffs and all the effects of a particular characteristic, but in the end a characteristic is either helpful to an animals chances to survive (and therefore makes the animal more fit) or not.
In the real world nobody needs to perform all these calculations. We, and the other animals, are born with certain characteristics and potentials, we develop, live, have children (or not), and die. Nobody needs to calculate which animals are fit, but their characteristics certainly do have an effect on their chances to live and the number of offspring they might have (which will inherit those characteristics, to some extent). Nature does not calculate what it is going to do, it simply does.
To claim that the "survival of the fittest" is a meaningless tautology, and so Darwinian evolution is meaningless or impossible, is to claim that inherited characteristics, like speed or strength, color of fur or plumage, and so on, are irrelevant to the chances for an animal to survive, have many offspring, and pass on those characteristics to it's offspring. That claim is simply false.
I do want to address a second passage from the www.alternativescience.com web site:
George Simpson, professor of paleontology at Harvard, [said] "If genetically red-haired parents have, on average, a larger proportion of children than blondes or brunettes, then evolution will be in the direction of red hair. If genetically left-handed people have more children, evolution will be towards left-handedness. The characteristics themselves do not directly matter at all. All that matters is who leaves more descendants over the generations. Natural selection favours fitness only if you define fitness as leaving more descendants. In fact geneticists do define it that way, which maybe confusing to others. To a geneticist, fitness has nothing to do with health, strength, good looks, or anything but effectiveness in breeding."
Notice the words; "The characteristics themselves do not directly matter at all." This innocent phrase fatally undermines Darwin's original key conception: that each animal's special physical characteristics are what makes it fit to survive: the giraffe's long neck, the eagle's keen eye, or the cheetah's 60 mile-an-hour sprint.
Simpson's reformulation means all this must be dropped: it is not the characteristics that directly matter -- it is the animals' capacity to reproduce themselves. The race is not to the swift, after all, but merely to the prolific.
The problem with this passage is that the author is trying to create a false dichotomy. Is the race to the swift, or is it to the 'merely' prolific? The answer is that it is a combination. Being swift can help you be prolific. If you are not fast enough to catch enough food to live then you will die and you will not be prolific. These are not independent things. The point Professor Simpson was trying to make (it seems to me) is that in the end a characteristic does not matter to a geneticist (or to evolution) unless it has some effect on the number of viable offspring produced. Professor Simpson uses an example of prolific red-heads. If red-haired people have more children, whether it is because red haired people more often live to breeding age, or more often find mates, or simply have more children when they do mate, then evolution will move in the direction of having red hair. The characteristic does not matter in itself -- the fact that it influences the number of offspring produced (possibly by influencing the survival chances of the person) is what makes it matter.
(This is also an argument against simple-minded eugenics, or labeling people as fit or unfit and trying to speed up evolution. The point is, we are not smart enough to know what makes an animal, or a person, fit. Nor do we possess the ability to predict what characteristics may be useful in the future. The best evolutionary security for a species is in maximum variety, not in trying to pick and choose the 'best' or 'fit' for breeding.)
In Professor Simpson's passage "effectiveness in breeding" is a combination of being able to survive to the point of finding a mate, being able to raise offspring to maturity, being able to find a suitable mate, and finally being capable of producing a number of offspring. The web page author tries to make it sound like only the final point matters in evolution, but this is clearly not the case, and not what Professor Simpson was saying. Producing many offspring is one possible strategy which can be used to be successful, or fit. However, an animal which produces 100 children, all of which starve before reaching maturity, is a genetic and evolutionary failure. An animal which produces only one child, but raises that child successfully to maturity and the point of having children of its own is a success, and far more "fit" (from an evolutionary standpoint) than the more prolific animal.