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 | "Evolution - Revolution" | |
| Perhaps this is as good a time as any to clarify two popular misconceptions. Evolution does not work in favour of the fittest species, it works upon individual members of a species. Nor has any previous creature been able to consciously influence its own evolution. An example may better illustrate this. In England, there is a type of moth that lives among Silver Birch trees. Its colouring is generally a pale silver that matches its surroundings; camouflaging them from predators. As in any gene pool, there are variations. Coloration among these moths varies from white to gray. The darker moths are always in the minority as they are more easily seen by sharp-eyed birds. The result is that not many moths that carry the genes for dark coloration survive to reach breeding age. Things changed with the coming of the Industrial Revolution. Factories belched out black smoke that descended onto the countryside in a gray pall, discolouring the trunks of the trees. The paler moths then stood out as a tasty hors d'ouvre for all and sundry. Fewer pale moths reached adulthood, the numerical ratio between the paler and the darker moths was reversed, and dark moths became the norm. With the passing of The Clean Air Act, the air did become cleaner, the trees whiter, and dark moths were back on the menu. Again, the paler members of the group are in the ascendancy. Nothing in that was planned. No conscious choices were being made. It is a typical case of certain genes prospering in a favourable niche. |
| Humanity, as most of us recognise it, has only been on the scene for a few thousands of years, but we have our roots in the earliest life forms known to us. It was only our incomparable ability to adapt to massive changes in the planet's ecology that allowed us to survive each of the several, near-total extinctions of life on earth. Individually we may be likened to the latest threads in a carpet that stretches so far back in time as to boggle the imagination. We are now the most complex, finely tuned mechanism of which we have knowledge. If one wishes to improve its performance or change its direction, a common-sense approach would dictate a passing degree of knowledge of its inner mechanisms. Particularly that of its guidance system, the brain. It is not my intention to delve into the fine details, only into the manner in which our various parts influence each other; the way these functions can be recognised by the effect that they have on us, and ways in which these can be put to our advantage. Let us return to the teeming seas and the life-less lands of the late Precambrian period to see how our many-times removed, great-grandparents are doing. Four billion years ago the warm seas of this planet were home to the first stirrings of life. These were the pre-Prokaryotic cells from which all life is descended. |
| Say hello to your forebears! They are worthy of acknowledgement, for they and their kind were to be the masters of all they surveyed, however dimly, for two billion years. Throughout that time, the environment remained relatively stable; and change only comes because of pressures. They thrived, those simple cells that resembled the blue-green algae we now see on stagnating ponds; but they were going nowhere. Trapped in an unchanging environment, they had reached their limits, drifting along as victims of chance. Their mistake was that, like us, they over-populated and poisoned their environment. Their own fecundity and the beneficent environment that allowed them to propagate in countless numbers, was to prove their undoing; bringing about the first of the near-total annihilations of all life on earth. It also set them on the road to producing us. In those warm seas, life appeared in small variations. Some of those variants formed symbiotic relationships, each partner deriving something of benefit from the association. During the long coalition, certain cells developed a nucleus, an internal package that contained their own DNA, the blueprints of reproduction. They also evolved internal structures for carrying out specific tasks. The advantage of symbiotic partners living together for mutual benefit is that, instead of each partner duplicating each others' chores, each one can tend to specialise at what it does best. As time passed, the partnerships became more intimate, until the stage came when one member completely engulfed the other to form a more complex organism. We shall never know how many of those variant couplings were to prove non-functional in the course of time. They have been written out of the pages of evolution. The two great success stories involved a photosynthetic prokaryote, and an aerobic bacterium - the mitochondria. Group one, the photo-synthesisers, constructed their nutrients from light and water. Group two, our direct forebears, obtained their nutrients by devouring the cells of other organisms. |
| By about 600 million years ago, the two types were clearly differentiated, although to this day the well being of the one is still closely related to that of the other. Every form of plant life that we now see about us, survives by photo-synthesis; the process by which sunlight, molecules in the air, and water are converted into carbohydrate reserves for maintenance and continuance. A by-product of the process is the manufacture of oxygen. The simple mitochondrion's sole talent is that over a vast period of time it had learned to provide energy-rich compounds by using oxygen to break down carbon-containing compounds into carbon dioxide and water; a much more efficient form of energy exchange than photo-synthesis. All life forms, including you and me, still contain mitochondrion in virtually every body cell. They still carry their own ancient DNA in a form quite different from the rest of us. They are one of many different life forms that act as crew in the vessels known as humanity. Without them, we could not exist. Without the mitochondrion, this planet would be a sterile ball. The mindless cells, thriving in the warm soup, were weaving their own death spell. At that time, the atmosphere was composed of Carbon Dioxide and Nitrogen, plus insignificant amounts of Hydrogen. However, a by-product of photosynthesis is Oxygen. Organisms that thrived in an anaerobic atmosphere were placed in mortal danger from even a low-level rise in the percentage of oxygen. |
| As the millennia passed, the oxygen levels rose to a point where life almost vanished. When we look at the White Cliffs of Dover, we are gazing upon the massed remains of minute ancestors. The only survivors were those who had absorbed into themselves the pre-Mitochondria, which had responded to the danger by evolving a biochemical method of respiration, based on oxygen. The march was underway. Moreover, the mitochondria have stayed with us every step of the way on the journey of 3 Billion Years. It is extremely important that we note that our first steps towards humanity were by way of accretion. We did not simply evolve from one discrete unit, improving parts of ourselves and discarding the prototype. That which evolved or we assimilated, stayed with us on the journey, becoming part of what we are. That is why the organ that we call, 'the brain', is really a collection of brains; each evolving to meet our needs at some stage of our development and becoming the foundation for the next brain to develop upon. At no time is there the suggestion that previous brains atrophied, withered away. Each of those brains still has its role to play, and each attempts to 'manage' us in a manner suitable to the external situation that existed at the time of its role as master of the machine. |
| The depopulated seas were no longer abundantly rich in food; so survival meant having an edge over the competition. If an organism adapted to feed on something too bitter to be enjoyed by anything else, it had found a niche. If the bitter food also made its own body too bitter to be eaten by others, it had developed a survival trait. Any number of combinations of cells could have come together. Merging of cells that shared among them such capabilities as being able to swim faster, store and metabolise a wider variety of food, appear threatening, or merge with the background, etc., increased the chances of living long enough to pass on those traits to their offspring. The gene pool was being shuffled like a deck of cards; with many combinations being discarded. The photo-synthesists were set to evolve into the world's plant life, and the non-photo-synthesisers had branched off on the long road to becoming the animal kingdom. A long road indeed, for it was another 230 million years before any creature emerged from the seas to become the first amphibians. From our point of view, the next important branching came at the end of another 50 million years of infinitesimal steps, with the emergence of reptiles, creatures that could finally spend their whole lives away from the primeval oceans. Another 90 million years of days and nights ticked by before the sun saw the first mammals walk the land. We were insignificant creatures, scurrying about between the legs of the dinosaurs. Dinosaurs diversified from a type of animal that we now refer to as the thecodonts, and in several ways were far more evolved than our then ancestors were. Many of them walked on their hind legs and were able to use their front limbs to manipulate objects with considerable dexterity. They were the lords of the earth and ruled for ~130 million years until, around 65 million years ago, there came another near total annihilation that wiped them from the record. |