Computers & Evolution
Computers & Evolution
COMPUTERS AND EVOLUTION
Copyright © 1983 by Bob B, All rights reserved
INTRODUCTION
It is now over a hundred years since Charles Darwin first formulated and later published his theory of evolution. The idea that earth's creatures descended from lower forms was not new with Darwin : one can find passages from ancient writings that refer to the concept. The special value of Darwin's theory was that it gave the first logical answer to how evolution worked : the famous principle of Natural Selection.
It was not long after the presentation of this new idea in the landmark book of 1859, The Origin Of Species, that religious leaders began to condemn Darwin and his "blasphemous lies". Clearly, the revealed truth of man's origin from the dust of the ground was in direct conflict with the claim that all life could be traced back to a common ancestor.
Since the early battles between religion and science over the idea of evolution, climaxing in the 1925 Scopes "Monkey Trial" in Tennessee, the conflict has subsided and is no longer newsworthy. And new evidence supporting the theory keeps accumulating to the point where the vast majority, even clergy, no longer doubt that evolution is a proven fact.
But quite recently the battle has begun to be heard again throughout the land. This time there is a difference though. Now the debate is between one scientist and another, with the clergy sitting along the sidelines being strangely silent. It is interesting that in these modern times the battle has started up again. To understand what all the shouting is about, we will need to review the scientific facts in the case.
The first part of this book will do just that. It will review what has been found in the past hundred years about the secrets of life, and how these discoveries relate to the theory of evolution. The fields of biology and genetics will be covered and the major findings summarized. At that point, with the main facts in hand, we will be ready for some speculation involving one of man's newest scientific inventions, the electronic digital computer. Although this machine has been with us for less than fifty years, it has already profoundly affected both our daily lives and our outlook on the future.
With the new information available to us about the inner workings of life, we can develop better approaches to understanding this wonderful and complex phenomena. We will see how it is possible to compare the genetic instructions that lie within the heart of each tiny cell with the programmed instructions which are at the heart of every functioning computer. But the extent to which this comparison will be able to shed new light on the workings of evolution will have to be left to future events to decide.
DARWIN'S THEORY
Darwin published his famous book in 1859, but he really had settled on his ideas much earlier than that. In 1831, as a young man, he sailed on the British chartmaking vessel, The Beagle, on a five year voyage around the world. As the scientific investigator on board, Darwin's job was to collect and study specimens of life from the strange varieties which he found in foreign lands. This data would later become the basic working set of information from which he would fashion his theory of Natural Selection.
That momentous event occurred within two years after he arrived home again in England. In October 1838, while reading Malthus' new book on the struggle for existence, Darwin realized that here was the mechanism for explaining the mysteries which he had seen on his voyage. The slight changes in various species which he had noticed while travelling from island to island, an observation that had so puzzled and intrigued him at the time, could finally be explained in a simple and logical manner. Natural Selection had been born.
Boiled down to its essentials, Darwin's theory stated that new varieties of life are selected by nature to become more numerous whenever that are better fitted to survive. This was later called Survival of the Fittest. And varieties which are less fit to survive become fewer and fewer in number and eventually become extinct. Over time there would tend to be gradual changes in the species which would better adapt them to their own particular environments.
One of the criticisms of the new theory was that the physical changes in offspring that Natural Selection would use to cause evolution would normally be very minor from generation to generation. Because of the long times involved, it would be very hard to prove conclusively that these small changes could add up over vast time spans to the larger changes actually observed.
Darwin recognized this problem and gave the following facts to provide support for his case. All animals seem to be related in their bone structures, organs and overall form. Breeders are able to rapidly "create" new strains by artificially selecting for desirable traits. Species separated by natural barriers such as mountains or water show distinct changes in size, coloring and shape. Fossil skeletons found in the rocks show a progression from simple forms in the lower, older layers to complex ones in the newer layers lying closer to the surface.
This last point is the critical one. It is the keystone supporting the evolution theory, because it is the major piece of irrefutable evidence proving that evolution has occurred. All of the other points are certainly in agreement with the idea of gradual, progressive change, but they are not conclusive by themselves. In combination with the fossil evidence, however, all observations point to a gradual evolution of life from a single ancestral form.
EVOLUTIONARY THINKING
Evolution theory is based on the common observation that there is a tremendous variety and variability of creatures, yet at the same time there is a remarkable similarity among all of these diverse life forms. The conclusion is then made that the only logical explanation for these similarities is that all current forms must have started out with a common ancestor. Darwin's genius was in coming up with a simple, logical and appealing reason for how so many different kinds of life could spring from a single original form.
From time to time various authorities have stated their views about evolution. Their writings reflect the progression of thinking on the subject over time.
Darwin wrote in 1859 :
... one might come to the conclusion that species had not been independently created, but had descended, like varieties, from other species .... I am fully convinced that species are not immutable, are lineal descendents of some other and generally extinct species ... I am convinced that Natural Selection has been the most important, but not the exclusive, means of modification.1
The authors of Science of Life wrote in 1929 :
Now, until a century or so ago, it was commonly believed that the world as we know it today had begun suddenly. It had been created .... In ancient, pre-evolution days it was believed that living things had been created in different "kinds" .... And a species, in particular, is no longer a unit created by God, nor is it a natural unit at all like the atom (?), or a quantum; it is an arbitrarily defined grouping set up by Man for his own convenience.... If there was no other evidence to sustain it, we should still have to believe that Evolution had occurred on the strength of the plan of the fossil record alone. 2
Sir Julian Huxley, the famous British evolutionist, wrote with regard to the history of evolutionary thinking :
However, as time went on the approach changed. The fact of evolution had been established and was no longer in need of further proof. Later, the underlying mechanisms of genetics and variation were discovered and the principal of natural selection was established as the method of evolution.3
One searches in vain through the various writings on evolution for a "scientific" definition of the term. In desperation, one turns to Webster's Collegiate Dictionary and finds the following :
... broadly, the process by which, through a series of changes, any living organism or group of organisms has acquired the morphological and physiological characters which distinguish it; hence, the theory that the various types of animals and plants have their origin in other pre-modifications in successive generations.
But perhaps the most modern and complete definition uncovered to date is one formulated by a lawyer whose hobby is writing about evolution :
On the basis of data drawn from comparative anatomy, embryology, and the experience of breeders, classical Darwinism asserted that the progression from the early species to the later ones, as observed in the rocks, was a process of actual physical descent governed by natural selection through such agencies as the struggle for existence, survival of the fittest, sexual selection, and adaptation, all of which worked in small, cumulative steps through vast periods of relatively undisturbed time.4 ---- Norman Macbeth
THE CELL
The human body is composed of as many as a trillion tiny living objects known as cells. Since each one of them is as small as a grain of sand, it is certainly not surprising that almost nothing was known about them until after the invention of the microscope. If we examine the structure of a cell under powerful magnification , we find that it is made up of many different parts : there are literally millions of different tiny objects moving around inside the cell doing many different things. It has been stated that a single cell is as complicated as a large city. As the
Nobel prize winner Sir John Kendrew has put it :
One of these (special kinds of difficulty) is the baffling complexity of even a single cell ... 5
For now, we will only be able to point out some of the more obvious and easily understood features of this amazing object.
One important part of the cell is its central core or nucleus. This is where we find the tiny threadlike chromosomes. Different kinds of life forms have different numbers of chromosomes in their cells, from one chromosome for the lowly single-celled bacteria, to 46 chromosomes for a human cell. Strung along each chromosome, like tiny beads on a string, we find the genes, the storehouses of genetic information. When a human egg cell becomes fertilized, it has received from the genes of the parents all of the information necessary to construct the final individual. All of the characteristics like eye color, shape of the nose, stature, skin color, and many others are predetermined by those tiny, tiny beads called genes. When someone notes a family resemblance in a child, he sometimes remarks that "its in their genes", meaning that they have inherited some physical feature which is distinctive to that family.
In addition to their job of controlling the development of physical characteristics, the genes store information on how to construct protein molecules. Protein is very important for supporting life, and the cells have the very complex job of manufacturing thousands of different kinds of protein molecules. They do this by using a "pattern" of the molecule stored inside a single gene. But the protein made by the cells of each species is unique to that species alone, so there must be billions of different protein molecules in the world.
We have seen that the instructions for building a specific kind of protein are stored in a single gene. If that gene happens to be defective, the cell will not be able to manufacture that type of protein and the person is said to be suffering from a "genetic disease". Luckily, everyone receives two of each kind of gene, one from the father and one from the mother, and only if they are both defective will we fail to produce that particular protein.
The process of making a protein molecule using the instructions from the gene works in the following manner. The gene is itself a long molecule, a chain composed of four different kinds of chemical links called nucleotides (i.e. DNA). The four kinds of links can be hooked up in many different ways, just as words and sentences are made up of different arrangements of letters. A unique gene "sentence", made up of a thousand or so DNA links, is decoded by the cell to construct a specific protein molecule. The process of going from the gene "pattern" to the final protein molecule involves cell particles called "ribosomes", "messenger RNA" and "transfer RNA". The cell can make any protein molecule for which it is furnished a gene "pattern", including ones for invading viruses. The formula for translating the gene "pattern" from its DNA sequence to the amino acid sequence of the protein molecule is called the "Genetic Code", and is the same for all life forms.
But as we shall see, the gene has one more job to do, that of controlling the development of multicelled organisms.
EMBRYO DEVELOPMENT
The field which deals with the development of multicelled organisms is called developmental biology. F.H.C. Crick, the co-discoverer of DNA replication, has defined the field as follows :
The aim of developmental biology is to explain as fully as possible how an egg and sperm are made, how they come together to form a fertilized egg, how the cell divides and divides again and again to form a small hollow of cells - the blastula; how this undergoes a complicated series of internal movements to form the gastrula, how the various cells change their shape and character to form tissues - and so on until the mature animal is built.6
This short description gives some idea of the enormous complexity of the process of embryonic development. Each embryo starts out as a single fertilized egg cell. As the cells divide and divide again, they reach a point where different types of cells: bone, blood, muscle, tissue, etc., are required. Somehow the cells seem to know how and when to form the required types, and also how to arrange themselves into the required structures. It is believed that the genes in each cell control this process, and that each cell is able to sense its position in the embryo and turn itself into the correct type of cell at the proper time. Sir Vincent Wigglesworth has described the role of the genes as follows :
... the genes as a whole constitute an hierarchical system, with genes in groups co-operating to give wide-ranging effects; genes controlling the timing of the activities of other genes; genes concerned in the formation of hormones which can bring about dramatic changes throughout the body; in short, a system of baffling complexity.7
Experiments have proven that each cell acts according to its own internally stored set of instructions. When cells from a developing animal embryo are experimentally moved to a different location during early stages, they are able to transform themselves into the appropriate size, shape and type to fit in with their new location. Similarly, certain animals are able to regrow severed limbs from the cells at the stump. And finally, a recent experiment successfully cloned an entire new toad by using the nucleus of a cell from the lining of the intestine to replace the nucleus of an egg cell.
These cases suggest several important things about the nature of the gene instructions inside each cell. These instructions stored in the genes are the same in each cell of the body, and are the complete set, capable of regrowing an entire individual. Only portions of this complete set of instructions are normally used by any particular cell, but each has access to the complete set if it is relocated as an embryo or later needs to regrow a severed limb. Information is passed to the genes from the world outside, so that they can tell the cell when to divide or to transform into a new type.
MUTATIONS
Sometimes, during the dividing of a cell, a copying error occurs which leads to a permanent change in the instructions in the gene. This change is known as a mutation and can be detected as a change in appearance or functioning of the organism. It is now known that certain factors can increase the rate of mutations. The most powerful of these so-called mutagenic agents are radiation, chemicals and heat. It was in 1927 that Hermann Muller proved that X-rays increase the mutation rate in fruit flys, an accomplishment for which he later received a Nobel Prize. Sometime later, the chemical colchicine was widely used to artificially create plant hybrids by doubling and tripling the normal number of chromosones in the nucleus of the plant cell. But, as Robert Cooke has stated :
... the great number of changes that do occur in genes turn out to be bad.8
The process of causing mutations by bombardment with radiation has been described by Hardin as follows :
Suppose ... you had a finely tuned racing car, and you stood ten paces from it and fired repeatedly with a shotgun : how likely is it that you would improve its performance ? It is extremely unlikely that we should in one short lifetime ... observe a new and good mutation that has never before occurred in any part of the world.9
So no one has ever been able to observe a "good" mutation. Despite this surprising lack of data, there is almost universal agreement that they do occur. In fact, their existence is needed in order for Natural Selection to be able to cause evolution. As Hardin writes :
... undesirable though mutation may be from a humane but shortsighted human point of view, it is.in the long run the primary creator of hereditary novelty on which the process of evolution depends.
And Cooke echoes this thought with the following :
This, then is how evolution has proceeded over billions of years, slowly selecting out good mutants that help strengthen a species, killing off the detrimental mutants which can't compete.
And Kendrew adds :
Ultimately, such a mutation (occasionally advantageous one) might be incorporated permanently into the books of life of that species. Such is the process of evolution.
SUMMING UP
We have reviewed some of the major findings about evolution and about life. In this process we have learned some interesting facts :
1. Cells are the basic building block of life, are extremely complex, and are absolutely vital to all reproduction, including that of viruses;
2. Development of multicelled creatures from an initial egg cell is a process so complex as to be virtually unknowable;
3. The making of most of the organic materials needed by the cells is done within the cells themselves using "patterns" stored in the genes;
4. Conversion from the gene patterns, which are the physical sequence of their nucleotides (DNA sequence), is done according to the "Genetic Code", which is the same for all life forms;
5. Proteins made by the cell are unique to each type of life form, despite the fact that cells typically make thousands of different proteins;
6. Evolution takes place due to Natural Selection of forms that are better fitted to survive, but needs to select from improved characteristics which come from mutation of the genes;
7. Mutations are copying errors which occur during gene replication, and are increased by radiation, chemicals and heat, but no one has ever proved the existence of a "good" mutation.
AN ANALOGY
Analogies are often used to help in understanding things. In physics, one sometimes compares the atom to a miniature solar system. And the human eye may be compared to the lens and film of a camera. Clearly, the two things compared are not the same, but there are enough similarities to make the comparison interesting and informative. Sometimes, the comparison is such that a new line of investigation is suggested, and it is this form of analogy that is the most useful of all.
A computer is a very powerful machine, some say that it is the most powerful ever invented. The computer can be instructed to do almost anything which can be imagined, from simple tasks like printing the payroll checks to complex ones like controlling the guidance system for a rocket to the moon. Recently, the computer has become very popular as the control box for video games such as PACMAN10 and DONKEYKONG.11 All of these very different jobs can be done using the same basic computer. All it takes is to use different instructions to handle each different job. The set of instructions for playing PACMAN is quite a bit different than the set used for playing DONKEYKONG. The computer is the same, only the set of instructions is different. Theoretically, even the job of printing the payroll checks and the job of guiding the rocket to the moon could be handled by the same computer which allows you to play the video game. But the sets of instructions for these jobs would be vastly different than for any of the video games.
What this suggests may come as a great surprise to some, but the computer program is considered by most experts to be more important than the machine itself. This is not to say that both are not necessary to carry out any activity, but the real "intelligence" of the combination lies in the instructions that are directing the computer in the carrying out of its activities.
An analogy is suggested here. We have seen previously that a cell will produce whichever protein molecule it is directed to by the genes. We might say that the cell is like a computer and the genes are like sets of instructions. In both cases, the instructions are directing the devices in the carrying out of a complex task.
It is amazing, but the cell seems to be like a living version of an electronic digital computer!
A PROGRAM
A computer program is a series or set of instructions which direct the computer in the carrying out of tasks. When the instructions are stored by the computer in its memory banks we refer to the computer by its full name : stored program digital computer. The instructions are stored as a group of numbers or digits, and the computer takes particular actions depending on the particular numbers which it receives. For example, the number 10 might be an instruction to add two numbers together and the number 11 might mean to subtract two numbers. A typical computer has a hundred or so different kinds of instructions like these.
The computer can store data (i.e. numbers) in its memory banks as well as storing instructions. When stored in memory, the instructions and data look the same, just a string of numbers. However, each of the instructions or items of data is stored in a different location in memory. Each has a different "room number", so that the computer can store or retrieve data by referring to its location number in the memory bank. A typical large computer might have a million different memory storage locations, while a small video game computer might have only a few thousand.
It is important that the computer has its instructions stored in memory along with its data. This means that the computer can add or subtract numbers from its own instructions; in other words, the computer can modify its own program. It is this property of a stored program digital computer which makes it so powerful, since this kind of computer can be programmed to react and adapt to its environment. This is one reason that a computer is so much more than just a high speed calculating machine.
As years have passed, computers have been programmed to perform more and more complex tasks. Programs to allow the computer to play chess have reached the point where only the best players in the world can now beat the machine. Recently, much has been written about a new field called "artificial intelligence". Programs to play chess are in this category, as are some of the video game programs that we mentioned before, but now people are beginning to find practical uses for these complex creations. One of these new programs which give computers "artificial intelligence" is able to assist a doctor to diagnose an illness. Another helps geologists locate likely sites for valuable minerals.
A video computer game that was recently announced is called Evolution.12 This game starts with a screenful of single-celled amoebas, and the player who is successful in winning the first game graduates to screens of mice, gorillas, and eventually to the final game with a human. This process of "evolving" from one creature to another in a computer game leads one to speculate whether it might be possible to simulate the development of an embryo. This is a very complex task, but who knows what computers might someday do?
A PROPOSAL
It is likely that the instructions in the genes of a cell are equivalent in complexity to a very large computer program containing millions of instructions. Previously, we talked about the fact that copying errors sometimes occur when genes are reproduced. But errors are also sometimes introduced when large programs are copied. The similarity of the two situations is so remarkable that it has suggested the following principal :
Sets of instructions with equivalent information content will have an equivalent likelihood of being improved by random change. --- Bob's Theorem
Surely, a computer program that is clever enough to duplicate the process of human embryo development has to have an information content equivalent to that contained in the genes! And if it is so, then we could experiment on this program by changing its instructions at random to see if this would "improve" the developing embryo which the program is simulating. Realistically, the problem could be approached in easier stages. We could first test a simple program to see if random changes would improve its operation, and observe how many trials it would take to achieve it. Then we could try more complicated programs , finding out by actual experiment the relationship between program complexity and the number of trials needed. Perhaps the results could even be calculated using mathematical techniques. Either way, it should be possible to establish whether "good" mutations are possible, and thus answer the question whether copying errors can lead to "good" mutations.
CONCLUSION
We have pointed out the similarities between the operation of the cell and the operation of the computer, and showed how the information content of their similar sets of instructions could be the same. Bob's theorem was stated as the principle that sets of instructions of equal information content will have equal likelihoods of being "improved" by random change. And finally, we proposed that this likelihood be studied experimentally by using carefully selected computer programs as laboratory "guinea pigs".
Past experience would lead one to believe that it would prove fruitless to try to improve a computer program by making random changes to its instructions. But why should we guess at the answer? Why not do the experiments and find out for sure? Who dares take up the challenge?
REFERENCES
1. The Origin of Species, by Charles Darwin
2. The Science of Life, by H.G. Wells, J.S, Huxley, G.P. Wells
3. Evolution in Action, by Sir Julian Huxley
4. Darwin Retried, by Norman Macbeth
5. The Thread of Life, by Sir John Kendrew
6. The Encyclopedia of Ignorance, article by F.H.C. Crick
7. The Encyclopedia of Ignorance, article by Sir Vincent Wigglesworth
8. Improving on Nature, by Robert Cooke
9. Nature and Man's Fate, by Garrett Hardin
10. PACMAN, Registered trademark of ATARI
11. DONKEYKONG, Registered trademark of COLECO
12. EVOLUTION, Video game by Sidney Development Corporation
