Natural selection, one of the most important theories in biology, was formulated by evolutionary biologist Charles Darwin in the 19th century.
The theory can be used to explain the imbalance on a particular body feature, or phenotype, among a population. A simple conceptualisation of this theory would be “survival of the fittest”.
There exist phenotypic variations among individuals in a population. Those possessing a certain phenotype are more adaptable to the living environment, and hence more likely to survive and reproduce. Consequently, an increasing proportion of the population will possess this favourable phenotype.
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In other words, nature determines the suitability of the phenotypes to exist in the environment, and selects those that are favourable to persist in the habitat.
But what if you were born unfit? Some organisms may choose to leave their birthplace and explore a new habitat that suits them better. Such migration can be dangerous as it depends on trial-and-error, and each migration can consume a lot of energy.
Alternatively, some organisms stay in the same habitat and become minorities in terms of the use of resources in the ecosystem.
Instead of competing hard with the fittest for a single resource that may seem to be abundant, they scavenge for less favourable resources. Such diversity can be seen as an act against the mainstream. Minorities certainly have a harder time surviving as fewer resources are available. Yet, as the consumption rate of these resources is lower, there is time for replenishment, stabilising the minority population.
On the other hand, the flourishing majority might overexploit the only resource they strongly depend on, which exceeds the rate of recovery of that resource. This would result in extensive deaths of the fittest. Besides, a lack of diversity would lead to lower adaptability to a changing environment.
When nature changes its selection criterion, the previously fittest population suffers while the minorities remain mostly unaffected. Thus, it seems harder for minorities to survive, but in fact they become the more tenacious members of the habitat.
Interestingly, natural selection is not confined to rationalising biological phenomena; some social behaviours progress in a strikingly similar manner.
What exactly those behaviours are, or how exactly this theory can simulate them, would depend on your interpretation. But it is clear that diversity is essential to true prosperity, and so it is no big deal to divert yourself from the mainstream.