Introduction
According to some scientists humans are subject to evolution by natural selection just as other organisms. However, humans are generally not subject to similar natural selection pressures experienced by other organisms. Humans have the capacity to handle the environment and are intuitive to manipulate their evolution through birth control systems.
Notably, the need to produce offspring is essential in evolution. For humans to have children there is a need to find a mate. Sexual preference is primarily significant and present in human as it is in other species. The presence of medicine, advancement in technology and shelter can not change the status of sexual selection in evolution. Human sexual desire and behaviors are not guided by the genetic make up of their mates but, by the culture they are in.
It is difficult to establish whether our genetic makeup guide culture. However, the presence of selective pressure means evolution will take place.
Patterns of evolution scientists argues that humans evolve by selection just as organisms. These scientists have taken their evidence from a study conducted on 39 individuals that was used to describe their genetic variation as well as the variation of between chimpanzees and the humans.
According to the pattern of evolution scientists, human evolution happened too fast because of the rapid increase in some genes. They add that the fact is, over a span of time irrevocable gene pool changes in all species. Humans are experience natural selection pressure but at a lower degree in contrast to other organisms.
On the other hand, humans take comprehensive measures that control birth rates; this controls evolution. Hence those considered having strong genes are not in a position to give them to the next generations. Through technological advancements, human is able to manage numerous advancements in medicine. Through these advancements humans who was once unable to get children being in a position of getting one. Humans are in a position to transform what is beneficial and what is not from time to time and are often unpredictably.
They have the ability to pick out certain effects as good or awful attributes and the ability to determine on what to use and what cast off. Evolutions have crafted human judgment and have become biased in judgments towards previously adaptive things. We have the potential to easily customize and improve our environment to suit our wants as humans. This makes it easy to bear up temperatures other organisms are not capable of. Human bodies are able to adapt to temperatures on every position of the earth. Humans do not have any natural predators, logically meaning they are not forced to evolve natural defense mechanisms for their survival from other organisms seeking to prey on them.
Convergent Evolution
This stands for a phenomenon where different species with contrary ancestry exhibits similar physical features. An excellent example is the sharks and dolphins. They are of different vertebrae groups yet there environments are similar. This has led them to evolve in to similar physical characteristics yet one is a fish while the other is a mammal. It is easy to note their coloration, shape of dorsal and location, the only thing that not similar are their tail flukes (Dobzhansky, 1973 pp 38).
Divergent Evolution
This is a case where relate species living in dissimilar environment becomes more and more unlike. Dobzhansky, (1973, pp 52) related species living in various territories tend to drift from separately. In long span of time they change in character this result to formation of new species. A good illustration is the Hyracotherium which evolved to numerous intermediary species like the zebra, mules and the horses. Currently the horses are not only divergent from the Hyacotherium but also from each other. Though they do not belong to the same species rabbits and maras ostensibly bear a resemblance to each other.
Coevolution
Co-evolution is combined transformation of species that interact closely. Predator and prey co-evolve and so do parasite and hosts. These parallel evolutions occur simultaneously. Dobzhansky, (1973, pp 52) take an example of an African cheetah and the Thompson gazelles. Cheetah has evolved to being the fastest mammal and reciprocally the Thompson gazelle is slightly less fast compared to its predator. Their speed increase simultaneously to enhance the chances of survival for both species
Gradualism
This is selection and disparities that occur gradually. Such changes are hardly noticeable over a short period of time. Slight changes on organisms that fit them better to their environment are selected. They are helpful traits of survival. The gradual variation is a slow continuous and steady process
Punctuated equilibrium
It is changes that develop in spurts. It entails a period of few changes and other period of enormous changes and is often through mutating genes of some species. The transmutations are disorganized adjustment of the species DNA. The DNA are not hereditary though they can be passed from generation to generation. A series of mutation result to a huge change
Conclusion
Coevolution, convergent and divergent evolutions are three major ways of evolution that occur when organisms are adjusted to the environment. They occur due to the constantly varying interaction amid species and their habitat.
There are various ways of selective pressures that may direct evolution. One of these ways is sexual selection and most of the other ways fall under a comparable group of natural selection. The evolutions of species are affected by natural selection in numerous aspects of their lives right from their development. Other aspects are the potential to reach reproductive phase.
Evolutionary scientists argue that whether we regard occurrence of evolution as a phenomenon that is enhanced by selective pressure or not, the dispute on whether humans are no longer evolving is futile in the knowledge of evolution as gradual work. Humans are varied, a main observation that they are being selected. With the progression of these selections will eventually lead to massive selection which may be applied in regard to our proceedings.
References
Dobzhansky, T (1973). Nothing in biology makes sense except in the light of evolution.