NaturalEvolution

It all began, down there in the deep blue oceans. Life spent its childhood there and grew slowly but steadily in an assiduous and unflagging way. From uni-cellular amoeba to the multi cellular crustaceans. And after a long time (seemed like eternity) came the fish, from fish, some became amphibians, others became mammals. From mammals came the primates and finally the supreme-human beings. The journey was a long, long one but was for the existence of life on this beautiful planet, and is still continuing. Indeed evolution is fantastic, and a mystery, that the human mind has not been able to reveal yet.

But all the answers lie in us - the human body - a remnant of all what has gone before us, in our past. The human embryo in the mother's womb is a mix of the embryos of different species from which the humans themselves have evolved during their transition from an egg to a baby. The three microscopic bones that connect our ear drum to our brain, the ones that carry vibrations - the smallest bones in our bodies are a perfect example of the magic of evolution. These very bones are a common factor in many species and serve varying purposes. For instance the same bones support the gills of a fish, a function primal for their survival. Another example is the magnificent human eye evolved over the years from animals to humans with such perfection unforeseen to humans themselves. The answers are within but we have been too non chalant in discovering them.

Scientifically evolution means the change in the gene pools of living populations of species which occurs over time. But Charles Darwin described it as the "Tree of Life". The green and budding twigs may represent existing species, and those produced during each former year may represent the long succession of extinct species...... From the first growth of the tree, many a limb and branch has decayed and dropped off, and these lost branches of various sizes may represent those whole orders, families and genera which have now no living representatives, which are know to us only from having been found in fossil state.

But how does evolution occur?

The three main mechanisms are mutation, natural selection and genetic drift. A mutation is any change in the DNA base sequence (genetic information) of a gene. However, only heritable mutations, those occurring in the gametes (reproductive cells) or the cell lineage contributing to the gametes, are involved in evolution. Such mutations, known as germinal mutations, can result from many factors, including natural background radiation, chemical mutagens and viral infection. Because only a small portion of the genetic sequence of the DNA molecule is used to code for proteins, most mutations do not result in new traits.

In the process of natural selection, individuals in a population who are well-adapted to a particular set of environmental conditions have an advantage over those who are not so well adapted. These individuals pass their genes and advantageous traits to their offspring, giving the offspring the same advantages. Generation after generation, natural selection acts upon each structure within an organ like the eye, producing incremental improvements in the process. In fact, any trait that increases the chances that an individual will reproduce, is providing a reproductive advantage, even if this comes at the expenses of the survival of the individual. For example, possessing a certain coloring pattern might increase an individuals chances of attracting a mate, but might also increase this individual's visibility to predators!

Genetic drift, is the process by which the frequencies of existing genes in a population change over time due to chance.

Evolution does not stop once a species becomes a species. Every population of living organisms is undergoing some sort of evolution, though the degree and speed of the process varies greatly from one group to another, Populations that experience a major change in environmental conditions, whether that change comes in the form of a new predator or a new island to disperse to, evolve much more quickly than populations in a more stable set of conditions.

Then comes the most important and interesting part of evolution - extinction. The age of the earth has been systematically and carefully divided in to a number of time periods which share common features. The nature follows a policy of experimentation, examination and then elimination. But first it experiments. New species of all shapes and sizes have roamed the surface of earth. So unusual, one cannot even imagine. Some entirely different and others a combination of others. In every time period nature did this and every time tested them with unexpected difficulties and in the end eliminated 90°c of them and thus only 10% of them ascended in to the next level assuring that the best adapted get an opportunity to face the challenges ahead. Extinction is often caused by a change in environmental conditions. When conditions change. some species possess adaptations that allow them to survive and reproduce. while others do not. If the environment changes slowly enough, species will sometimes evolve the necessary adaptations, over many generations. Of all species that have existed on Earth, 99.9 percent are now extinct. Many of them perished in five cataclysmic events.

The current mass extinction has been unfolding for millennia. and unlike the greenhouse effect, global warming, or the hole in the ozone layer, it is visible without sophisticated imagery or complex computer modeling. It is real, and it is happening to a greater or lesser degree all over the globe; it is most apparent, however, in the tropics. It will not eliminate life from the Earth; no mass extinction does that. But enough species will die that the nature of life on the Earth will be forever changed. Many scientists dispute whether an extinction is currently taking place at all, or suggest that we are facing the prospect but have not yet begun the experience. Others agree that we are indeed in a period of increased extinction. but that the net result will little change the Earth's flora and fauna. I do not share such a sanguine view. I believe that the current extinction is well underway, having started with the dawn of the ice age, about 2.5 million years ago, and since then accelerating its rate of species destruction. In some ways it is very much like the dinosaur4dlling event of 65 million years ago, when a biosphere already ,stressed by rapid changes in climate and sea level was knocked in to mass extinction by the impact of asteroids, striking, according to new evidence, simultaneously in North and Central America. A very similar scenario is currently unfolding. Over 2 million years ago, giant glaciers began to cover large portions of the planet, changing climate and sea level on a global scale in the process. And then. 100,000 years ago, another great asteroid hit Earth, this time in Africa. That asteroid is named Homo sapiens.

In the battle against infectious disease, humankind has inadvertently given rise to deadly enemies. Antibiotic resistance is a stunning example of evolution by natural selection. Bacteria with traits that allow them to survive the onslaught of drugs can thrive. re-ignite infections, and launch to new hosts on a cough. Habitat destruction is the leading cause of endangerment and extinction. But while there are remote ocean areas that remain relatively pristine, most coastal areas have undergone a radical human -induced transformation in the last 100 years. We human beings have really been a bane for our nature. The evidence all points to a global tragedy with a profound loss of biodiversity. As human population pressures grow, essential ecological services species are affected leading to conditions in which the planet's vital organs can serve neither nature nor us.

1lie most intelligent species nature created, and I am sure would be very proud of also, would be ashamed to see that that this wonderful creation has led to such destruction of others. But will it lead to our own extinction? A daring scientist once stated this daring theory that humans will perish by the end of this time period and, to my astonishment he had written, that rats and cockroaches would survive and proceed, (owing to their versatility in choosing habitats). But he must have forgotten that humans have best adapted to their environment even though manipulating it tremendously. We now adapt to crowding, pollution, and new diseases rather than the necessity to escape from large predators. Humans will change in the future, but are unlikely to evolve in to a new, separate species because no human group is truly isolated anymore, given our transportation systems. Without genetic isolation, there is no further opportunity for speciation among humans, I hope this dire prediction will not come true. But nobody knows what nature has got in store for us.

Evolution has happened, evolution is happening and evolution will continue to happen.