Natural selection says only the fit will surprise, also known as survival of the fittest. Fit are those that have the inherited traits that help them best adapt to their habitat so that they live long enough to have and raise their offspring. Does this mean all of the inheritable traits of organisms ultimately serve one purpose: improve the adaptation of the organisms to their environments? Are All of Our Traits Evolutionary Adaptations?
All species have such immense potential fertility that their population size would increase exponentially if all live-born individuals were to go on to successfully reproduce. However, populations of species tend to remain stable in size, except for seasonal fluctuations.
Not all individuals born go on to reproduce successfully because there is a continuous struggle for existence among individuals of species. This struggle is not only against environmental conditions, and other species but also against each other for food, and shelter.
Individuals of a species that have developed favorable traits to help them with their struggle for survival are more likely to survive long enough to pass on their genes, and as a result, over generations, the species become more and more adapted to its habitat.
The Missing Link That Never Was
In his 1859 book “On the Origin of Species”, Charles Darwin called the mechanism that gradually changes the characteristics of species and makes the species more adaptable to their environment as “natural selection”. However, it wasn’t before 1864 when Herbert Spencer coined the phrase “survival of the fittest” in reference to “natural selection”. Although his peers advised Darwin to use “survival of the fittest” instead of “natural selection” to make his ideas more clear, Darwin used natural selection and survival of the fittest interchangeably but never abandoned the use of “natural selection” altogether.
The characteristics that make species, including humans, “fit” are not universal. These characteristics vary in every population, based on environmental factors. Therefore, the individuals that survive in a given population are not necessarily the smartest, the strongest, the largest of the population but they are adapted well enough to their environment to survive and reproduce.
Loss of Evolutionary Traits
Natural Selection weeds out traits that adversely impact the survival chances for an individual to have their offspring. In other words, for an individual to survive, the favorable traits of the individual must be just about good enough, not necessarily good, or progressively better.
For example, if not being as muscular as, as fast runner as, or as strong biter as their ancestors do not prevent individuals from passing on their genes, then over time the species may or may not lose those traits.
Modern Humans are a relatively weak species; our closest cousins, chimps, can easily shred us into pieces. We cannot run fast, we are louse tree climbers and we have thin skins, bad teeth. Our hearing and vision are not all that great, to begin with, and little what we have quickly parish as we age.
New Inheritable Traits Born
Human reproduction cells, namely, eggs and sperms, inevitably mutate over time. In most cases, these mutations have a negative impact on the offspring which are eliminated by natural selection. The remaining rare mutations that result in favorable or not relevant traits join the human gene pool.
Thanks to adaptive traits humans have big brains, complex societies, we have little body hair, and an excellent body cooling system. Even if we cannot run as fast as some other animals in the kingdom, we can walk and run with comparatively little need for rest long hours. We can play tricks on our praying animals and then kill them from a distance with the tools we build. Individually our strength is not impressive, but when we cooperate with each other we rise to the top of the food chain.
On the other hand, because it is not relevant to the natural selection of humans we have cosmetic traits such as various eye and hair color genes, or ABO blood types, such traits are not adaptations. Non-adaptive traits stay in human gnome because it does not adversely affect the survival chances of an individual.
Are All of Our Traits Evolutionary Adaptations?
If its habitat under stable conditions were to be a perfect match for a species, including homo sapience, the evolution of the species would slow down but never stagnate. The main reason for this is the fact that given enough time, it is ultimately improbable that a species does not develop non-adaptive traits. One of the best observable examples for non-adaptive traits is the human eye color.
Originally, all humans had brown eyes before they left Africa. However, less than 10,000 years ago in the northwest part of the Black Sea region humans with blue eyes emerged.
Blue eye color was a result of a genetic mutation affecting the OCA2 gene in our chromosomes. This mutation resulted in the creation of a “switch,” which literally “turned off” the ability to produce brown eyes. The result is that Accordingly, humans who inherited this mutated OCA2 gene both parents possess blue eyes instead of brown eyes.
The mutation of brown eyes to blue represents neither a favorable nor a unfavorable mutation. It is one of several mutations such as hair color, and baldness which neither increases nor reduces a human’s chance of survival to pass on their genetic information.