Q.When we say "survival of the fittest", does it mean that
a. those which are fit only survive, or
b. those that survive are called fit?
Comment.
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Start your 14-day free trial to unlock the full solution →The phrase “survival of the fittest” is often misunderstood as meaning that only the physically strongest or most aggressive individuals survive. In reality, it describes a process where organisms that happen to be well-suited to their environment are more likely to survive and reproduce — and those survivors are then called “fit” in retrospect.
The idea of “survival of the fittest” was popularised by Herbert Spencer after reading Charles Darwin’s On the Origin of Species, and Darwin himself later used the phrase. But the phrase has caused endless confusion. Many people imagine a brutal, winner-takes-all contest where the biggest, fastest, or fiercest creature wins. That is not what Darwin meant, and it is not what modern biology teaches.
Let us look at the two options you have given.
Option (a) — “those which are fit only survive” — suggests that there is a fixed, pre-existing standard of fitness, and only those who meet that standard get to live. This is misleading because fitness is not an absolute quality. An organism is not “fit” in general; it is fit for a particular environment. A polar bear is magnificently fit for the Arctic but would quickly die in a tropical forest. A cactus is fit for a desert but would rot in a rainforest. So there is no universal checklist of fitness that organisms must pass. Instead, fitness is always relative to the surroundings.
Option (b) — “those that survive are called fit” — comes closer to the truth, but it can sound circular if stated carelessly. It seems to say: “The survivors are fit because they survived, and they survived because they were fit.” That is indeed a tautology if we do not define fitness independently. However, biologists avoid this trap by defining fitness in terms of differential reproductive success. An organism is considered fit if it leaves more offspring that themselves survive to reproduce, compared to other individuals in the same population. Survival is only one part of the story; reproduction is the key.
In NCERT Class 12 Biology (Chapter 7, Evolution), the concept is explained clearly: “Fitness is the ability of an organism to survive and reproduce in its environment.” So survival alone is not enough — an organism must also pass on its genes.
Now, consider a real example. In a population of beetles, some are green and some are brown. If the ground is brown, birds can spot green beetles more easily and eat them. The brown beetles survive better and produce more brown offspring. Over generations, the population becomes mostly brown. Were the brown beetles “fit” before the birds arrived? No — they became fit because the environment favoured them. And after the change, we call them fit because they survived and reproduced. So the environment decides what counts as fit, and the survivors are the ones that happen to match that environment. …
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