Evolution, the science of how populations of living organisms change over time in response to their environment, is the central unifying theme in biology today. Evolution was first explored in its semi-modern form in Charles Darwin ‘s 1859 book, Origin of Species by means of Natural Selection. In this book, Darwin laid out a strong argument for evolution. He postulated that all species have a common ancestor from which they are descended. As populations of species moved into new habitats and new parts of the world, they faced different environmental conditions.
Over time, these populations accumulated modifications, or adaptations, that allowed them and their offspring to survive better in their new environments. These modifications were the key to the evolution of new species, and Darwin proposed natural selection or “survival of the fittest” as the vehicle by which that change occurs. Under Natural Selection, some individuals in a population have adaptations that allow them to survive and reproduce more than other individuals. These adaptations become more common in the population because of this higher reproductive success.
Over time, the haracteristics of the population as a whole can change, sometimes even resulting in the formation of a new species. Humans have survived for thousands of years and will most like survive thousands of more. Throughout the history of the Huminoid species man has evolved from Homo Erectus to what we today call Homo Sapiens, or what we know today as modern man.. The topic of this paper is what does the future have in store for the evolution of Homo Sapiens. Of course, human beings will continue to change culturally; therefore cultural evolution will always continue; but what of physiological evolution?
The cultural volution of man will continue as long as man can think; after all it’s the ideas we think up that makes up our cultures. In a thousand years man might complete a 180 degree turn culturally (not to mention physiologically) and as seen by our fellow inhabitants of earth we would in essence be different beings. One can say that this new culture has chosen its ideas based on Natural Selection. One can see this in the spread of ideas in the past history of homo sapiens, the ideas which cause man to succeed are chosen such as science and democracy (the present growth of Islam is also worthy of mention, but would be a aper in itself).
Lamarck’s fourth law, that is, ideas acquired by one generation are passed on to the next, describes this transfer of ideas from one generation to another. The question is can humans evolve (physically), that is through changes of some sort to the general human gene pool, enough to be considered a different species sometime in the future. The answer to this is tricky. The answer is “yes” if there is no human intervention and “not likely” (or atleast controlled) if there is human intervention. The more interesting answer is the latter. The first answer deserves some mention.
Through the subtraction or addition (that is through chance changes of some sort) of alleles (different forms of a characteristic gene) from the overall gene pool until homo sapiens are no longer is feasible. One might ask how and were this is occurring. The answer is human genes are changing all the time through radiation and spontaneous mutations (the latter more rapidly no than ever since the human population is now larger than ever) and one can see these changes to the overall gene pool in the disappearance of certain human tribes within parts of Africa and South America..
These tribes unfortunately take exclusive alleles with them. What about Natural Selection in present human culture. Some peoples are growing faster than others, for example-Chinese faster than any other in the present world, thus the large Chinese population. Therefore some group traits ae more common than others. Yet the loss of these alleles and the gain of these mutations offer marginal contributions to our species and thus have little or no effect. The first step in understand evolution in present terms is to mention genetic engineering (including genetic drift).
The first step to understanding enetic engineering, and embracing its possibilities for society, is to obtain a rough knowledge base of its history and method. The basis for altering the evolutionary process is dependant on the understanding of how individuals pass on characteristics to their offspring. Genetics achieved its first foothold on the secrets of nature’s evolutionary process when an Austrian monk named Gregor Mendel developed the first “laws of heredity. ” Using these laws, scientists studied the characteristics of organisms for most of the next one hundred years following Mendel’s discovery.
These early studies concluded that each organism has two sets of character determinants, or genes (Stableford 16). For instance, in regards to eye color, a child could receive one set of genes from his father that were encoded one blue, and the other brown. The same child could al so receive two brown genes from his mother. The conclusion for this inheritance would be the child has a three in four chance of having brown eyes, and a one in three chance of having blue eyes (Stableford 16). Genes are transmitted through chromosomes which reside in the nucleus of every living organism’s cells.
Each chromosome is made up of fine strands of deoxyribonucleic acids, or DNA. The information carried on the DNA determines the cells function within the organism. Sex cells are the only cells that contain a complete DNA map of the organism, therefore, “the structure of a DNA molecule or combination of DNA molecules determines the shape, form, and function of the [organism’s] offspring ” (Lewin 1). DNA discovery is attributed to the research of three scientists, Francis Crick, Maurice Wilkins, and James Dewey Watson in 1951.
They were all later accredited with the Nobel Price in hysiology and medicine in 1962 (Lewin 1). “The new science of genetic engineering aims to take a dramatic short cut in the slow process of evolution” (Stableford 25). In essence, scientists aim to remove one gene from an organism’s DNA, and place it into the DNA of another organism. This would create a new DNA strand, full of new encoded instructions; a strand that would have taken Mother Nature millions of years of natural selection to develop. Isolating and removing a desired gene from a DNA strand involves many different tools.
DNA can be broken up by exposing it to ultra-high-frequency sound waves, ut this is an extremely inaccurate way of isolating a desirable DNA section (Stableford 26). A more accurate way of DNA splicing is the use of “restriction enzymes, which are produced by various species of bacteria” (Clarke 1). The restriction enzymes cut the DNA strand at a particular location called a nucleotide base, which makes up a DNA molecule. Now that the desired portion of the DNA is cut out, it can be joined to another strand of DNA by using enzymes called ligases.
The final important step in the creation of a new DNA strand is giving it the ability to self-replicate. This can be accomplished by using special pieces of DNA, called vectors, that permit the generation of multiple copies of a total DNA strand and fusing it to the newly created DNA structure. Another newly developed method, called polymerase chain reaction, allows for faster replication of DNA strands and does not require the use of vectors (Clarke 1). Genetic drift, another important factor when discussing evolution, is the study of statistical population genetics. . One aspect of genetic drift is the random nature of transmitting alleles from one generation to the next given hat only a fraction of all possible zygotes become mature adults. The easiest case to visualize is the one which involves binomial sampling error. If a pair of diploid sexually reproducing parents (such as humans) have only a small number of offspring then not all of the parent’s alleles will be passed on to their progeny due to chance assortment of chromosomes at meiosis.
In a large population this will not have much effect in each generation because the random nature of the process will tend to average out. But in a small population the effect could be rapid and significant. Suzuki et al. explain it as well as anyone I’ve seen; “If a population is finite in size (as all populations are) and if a given pair of parents have only a small number of offspring, then even in the absence of all selective forces, the frequency of a gene will not be exactly reproduced in the next generation because of sampling error. If in a population of 1000 individuals the frequency of “a” is 0. in one generation, then it may by chance be 0. 493 or 0. 0505 in the next generation because of the chance production of a few more or less progeny of each genotype. In the second eneration, there is another sampling error based on the new gene frequency, so the frequency of “a” may go from 0. 0505 to 0. 501 or back to 0. 498. This process of random fluctuation continues generation after generation, with no force pushing the frequency back to its initial state because the population has no “genetic memory” of its state many generations ago.
Each generation is an independent event. The final result of this random change in allele frequency is that the population eventually drifts to p=1 or p=0. After this point, no further change is possible; the population has become homozygous. A different opulation, isolat ed from the first, also undergoes this random genetic drift, but it may become homozygous for allele “A”, whereas the first population has become homozygous for allele “a”.
As time goes on, isolated populations diverge from each other, each losing heterozygosity. The variation originally present within populations now appears as variation between populations (Suzuki 704). The evolution of man can be broken up into three basic stages. The first, lasting millions of years, slowly shaped human nature from Homo erectus to Home sapiens. Natural selection provided the means for countless random mutations esulting in the appearance of such human characteristics as hands and feet.
The second stage, after the full development of the human body and mind, saw humans moving from wild foragers to an agriculture based society. Natural selection received a helping hand as man took advantage of random mutations in nature and bred more productive species of plants and animals. The most bountiful wheats were collected and re-planted, and the fastest horses were bred with equally faster horses. Even in our recent history the strongest black male slaves were mated with the hardest working female slaves.
