The change in genetic material of a population of organisms and its accumulation over generations leads to adaptive evolution of an organism and origin of new species. The genetic pool of a sexually reproducing organism varies between individuals of even same species. The forces of natural selection favor the variations which provide adaptive fitness whereas selection occurs against unfavorable variations. Hence, over generations the favorable traits are increasingly accumulated leading to increased adaptation of an organism to its surroundings. Hence, in addition to ensuring survival, the adaptation should also ensure efficient reproduction to pass on the favorable traits to successive generations and create newer variations. These explanations for evolution were put forth by Charles
Darwin and have been confirmed with increasing evidences.
Since reproduction ensures successive generations with more evolved offspring, evolution can be seen as fertility averaged over a long period of time. The essential crux of sexual reproduction that leads to adaptive evolution is its ability to produce genetic variations. The genetic variability maximizes heterozygosity with each new generation. Heterozygosity is very beneficial, as it decreases the incidence of genetic abnormalities and most importantly improves the fertility. It is not known how heterozygosity increases fertility, but evidence from many organisms supports the association. Hence it can be said that with evolution of an organism there also occurs an increase in its fertility. On the other side, the increase in fertility can enhance rate of evolution by producing more offspring. Essentially, the evolution and fertility can be called two sides of a coin which cannot be separated. Contrary to this, a decrease in fertility will lead to decrease in rate of adaptive evolution.
During last few decades the human male fertility has declined rapidly as evidenced by decrease in sperm count and semen volume due to changes in lifestyle and environmental conditions.
his reduction in fertility is gradual and will continue as the environmental changes are getting worse. The reduced fertility has not affected human population growth, which indicates that the fertility is still optimal. On the contrary, the gradual decrease of fertility may affect the rate of adaptive evolution of humans over next generations.
One of the human technologies which adversely affect the human fertility is mobile phone radiations. The mobile phone radiations affect sperm number, sperm density, sperm motility and sperm morphology leading to impaired fertility. These damages occur even after exposure is of short duration. The decrease in cost of production of mobile phones and effective advertisement strategies has ensured that every individual can afford a personal mobile phone. The effects of mobile phone usage on male fertility are so striking that they have been called even the nemesis of modern man. This means that the human fertility is further decreasing which may adversely affect our adaptive evolution.
The mobile phone usage can be compared to cancer in terms of their effects on the human survival. Cancers are presently not treatable and lead to mortality whereas mobile phone usage is presently not preventable and lead to decreased fertility. A common man may perceive cancer as more dangerous than mobile phone. However Darwin would choose to kill the mobiles phones over cancers as former affects fertility (ultimately affects rate of adaptive evolution) while latter usually strikes after the fertility no more matters (most cancers affect aged individuals).
