Human Origins

The Evolutionary Process

Evolution as a process is composed of two parts:

1. An organism reproducing mechanism that provides variable organisms. Changes to the organism are largely random and effect future generations. They are made without regard to consequences to the organism.

2. A changing environment which screens organism changes. The environment provides stress on the variable organisms that selectively allows, through competition, certain changes to become dominant and certain others to be eliminated, without consideration for the future of the mechanism. That same process provides mechanism (organism) disintegration if a strong screening environment is not present. Evolution is a two-way process which does not always work to the long term advantage of the organism and in fact often becomes quite deadly to a given species and thereby eradicates it.

The evolutionary process is bidirectional in its effect. It may, depending on the environment, either improve a given characteristic or decay it. Since the first step in the process is largely random and most organisms are quite complex, almost all of the variations are harmful. A characteristic of a species advances if the environment is harsh, since most harmful variations to that characteristic will be eliminated through death and suffering at a rapid rate, leaving only the inconsequential and helpful changes in the lineage. If the environment is benign with respect to the capability of the species then the harmful changes are not eliminated and the species will degenerate to a point of balance with the environment.

:: The Evolutionary Mechanisms

Evolution is the change with time of the gene pool of a species. The mechanisms of evolution are mutation, natural selection, recombination and gene flow.

Mutation provides all initial change. A mutation occurs when the DNA does not replicate perfectly. When a mutation occurs, a new allele is created. As a first approximation, these accidents (mutations) are random (can occur at any location along the DNA). The rate of these accidents is relatively constant within a given species. If the accident occurs in a critical location (believed to be less than 10% of the total in man), the result is usually disastrous. Other areas will accept change with no immediate consequence. Once made, the mutation is perpetuated and variability within the gene pool of the species is increased. Mutations add variability to the gene pool.

Natural selection occurs when the viability of an allele is tested in real life. It makes only one test. Contrary to popular opinion, evolution does not select the fittest, strongest, or most superior organism. It is instead a question of how many offspring the organism will have which in turn will reach sufficient maturity to have its own offspring. If the effect is positive, the allele will become a permanent part of the gene pool. If the effect is very successful, it will quickly become a dominant allele. If the effect is neutral or negative, the allele will not spread rapidly through the gene pool and, usually, will disappear from the gene pool. If more than one mutation is being tested at the same time, usually the case, then it is the summed effect tested. Not all good mutations make it. Some mutations would be good at one time and bad at another, depending on the environment then. A mutation that was necessary at one time may become unnecessary at another time and be consequently negated. Most of the time, the alleles removed or negated are those that harm the organism in that environment. Natural selection removes variability from the gene pool.

The environment which an organism faces and must survive is a complex one, one which is more than climate and food supply, although those are the essential elements that serve as a starting point in the study of evolution.

First of all, the mutation process is not altogether random. An intricate process called recombination developed early in sexual animals. This process serves to mix the alleles available in the two parental gene sets to provide more variability against the environment. It also results in many reproduction errors (mutations). Repair functions were developed by evolution for DNA errors to offset this error propensity. Since both the dissection means and the repair means are relatively fixed processes, then both the dissection errors and the errors in repair will follow certain patterns. When these coincide, a new allele is formed. Mutations, then, occur in clusters around particular loci not yet known or cataloged. Certain defects occur, therefore, with a given frequency, which are wholly the result of the process and not the assumption of a defective ancestral gene.

Another factor which enters into genetic change is that the product of a purely random process (and a large part of human mutations fit that description) will drift to one side or another until an outside force interferes with the drift. For example, the human is now growing larger. If this is the result of genetic drift, it will continue until some other process interferes, such as a shortage of food.

Most of the struggle in life is the struggle for enough food to avoid starvation and an ability to survive the climate. This was the entire struggle at the beginning, but as life became more complex, the selection process also became more complex. Once life began, however, other life became a part of its environment. The food chains were started.

The basic element of species survival is the ability of the individual to survive long enough to insure the survival of its offspring to the point when they also have offspring. If the offspring require no care, then the immediate death of the parent is of no consequence. In the case of the higher animals, those which require care during their maturation, the life of the caring parent must extend through that maturation period (and, of course, the parent must perform its function properly).

If an animal must endure an environment in which its population is normally controlled by predators, it is usual that the young suffer a higher death rate than the adults. In such cases the parents will usually live through several breeding seasons, to offset losses of their young. Some animals resort to large numbers of offspring, thereby feeding the predators, with enough left over to continue the species.

As animals became more complex, they themselves began to be an appreciable part of their own selection (survival) environment. Herein lies the most complex of all genetic processes, and examples abound. Sexual selection (based on an appearance which is sexually attractive) is probably (not for sure) the most common of these. There are times when sexual selection actually harms the ability of the species to survive. There are thousands of examples, but to select one, consider the Cardinal, a beautiful small bird that is quite common in North America. Somewhere back in time, the drab little hens, who had drab little roosters as soul-mates, took a liking to the color red and began choosing mates based on a hint of red in their feathers. Since they mated with roosters who had red in their makeup, their offspring tended to have red in their feathers, which suited the next generation of hens just fine. Quite quickly the rooster was a bright red, and the best target in the world for a predator. The predator, usually a hawk, could lock on to that bright red target and have a meal in no time. As a result the Cardinal rooster is quite skittish, and he should be, but without the red there is no sex and his genes end.

Recombination occurs in sexually reproducing organisms, such as the human. The parent has two sets of chromosomes in each cell, one from its father, the other from its mother. The sperm and the egg carry only one set in each. The one set carried by the sperm or egg is not a whole set from either grandparent but is a mixture of the two. Both original sets of chromosomes, in the case of each parent, are dissected and scrambled, then reformed with entirely new combinations of alleles from both grandparents. This process adds variability to the offspring and allows testing of new allele combinations. Recombination allows new combinations of the variability in the gene pool

Gene flow occurs when populations of a species that have been separated are united and the differing sets of alleles in each gene pool flow into the gene pool of the other. Our species, suddenly reunited with widespread transportation, is an excellent example of this effect. Gene flow distributes the variability in the gene pool.

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