Biology - Other

Are Humans Evolving – Evolving



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Although there are no large scale studies to support the idea that the human race is continuing to evolve, there have been scientifically recorded instances of minor changes in anatomy and physiology which could suggest that this is the case. Whether these minor changes are the result of genetic changes, which are significant from an evolutionary viewpoint, cannot be ascertained with any accuracy. We have only recently mapped the whole human genome and cannot be sure exactly which genes have changed over time. Where gross changes in human genetics have occurred in the recent past, they have usually been linked to abnormalities such as Downs' Syndrome, produced by a doubling of one of the twenty three pairs of human chromosomes. Many genetic changes have proved to be fatal as with the case of mutations produced by exposure to excessive doses of nuclear radiation.

According to neo Darwinians evolution is based on small changes in the genetic make-up of a species which provide an advantage for reproductive survival and are consequently passed on to future generations. Within any viable human population, individuals which demonstrate 'superior' survival traits, as a result of genetic changes, produce an increase in the incidence of these genes within that population. The environment is seen as the mechanism which normally selects which traits are 'fitter' than others. The incidence of fairer skin in northern environments is seen to be a consequence of the need to maximize the beneficial effects of sunlight in the production of vitamin D. Although all humans have roughly the same concentrations of melanophores in their skin, genes control the activity of these melanophores and produce changes in skin color normally associated with differences in geographic location.

Differences in skin color don't make for the type of major changes in genetic make-up which constitute a new species. The generally accepted definition of a species is that members of the same species are able to reproduce and produce fertile offspring under natural conditions. Horses can be crossed with donkeys to produce mules, but the mules are sterile and therefore are not classed as a new species. Other sterile hybrids are known and indeed are very useful particularly in the plant kingdom. Animals which normally are unable to reproduce because of geographic separation, or aversion to mating with each other, have produced fertile offspring in suitably contrived situations. According to the generally accepted definition of a species such contrived offspring may not be considered as a new species.

Given the ability of most races of human beings to intermarry and produce fertile offspring, the chances of a trait arising which will produce a new species appears highly unlikely. Thousands of years ago it was thought that Neanderthal man and Cro-Magnon man were two different species of humans. However, recent archaeological evidence suggests that their habitats overlapped and it is likely that they intermarried and produced fertile offspring. Evidence of other species of 'humans' like Homo habilis and Homo erectus, and even more primitive forms; suggest a link with a common ancestor who gave rise to both humans and the great apes. The fact that the great apes and man have over ninety percent of their genome in common with each other is used to support the idea of human evolution. Creationists do not agree with the idea of human evolution and consider modern man to have devolved from the human form originally created by God. Whether man has evolved from a common ancestor with the great apes or was divinely created in a form more perfect than he is currently, does not provide any evidence for or against any future evolution of the species.

Under natural conditions and without divine intervention Homo sapiens sapiens appears unlikely to evolve further. However, given the human predilection for experimenting with reproduction, some would say meddling; this does not preclude the formation of a new species of 'human' by some other means. Modification of the human genome by the removal of 'unfavorable' genes and the insertion of more 'beneficial' genes is no doubt already underway in some parts of the world where this is allowed. In order to evolve a new species of human able to survive a range of environmental factors such as exposure to deadly viruses, severe atmospheric pollution, or the stress of extended space travel, 'beneficial' genes may eventually be selected from other species. Whether or not such a new species is truly human is a matter which future generations will have to grapple with.

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