Start Date: May 4, 2003 Finish Date: May 18, 2003

WHEN on board H.M.S. Beagle as naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America, and in the geological relations of the present to the past inhabitants of that continent. These facts, as will be seen in the latter chapters of this volume, seemed to throw some light on the origin of species- that mystery of mysteries, as it has been called by one of our greatest philosophers. On my return home, it occurred to me, in 1837, that something might perhaps be made out on this question by patiently accumulating and reflecting on all sorts of facts which could possibly have any bearing on it. After five years' work I allowed myself to speculate on the subject, and drew up some short notes; these I enlarged in 1844 into a sketch of the conclusions, which then seemed to me probable: from that period to the present day I have steadily pursued the same object. I hope that I may be excused for entering on these personal details, as I give them to show that I have not been hasty in coming to a decision.

-- Charles Darwin [*1]

Section I: Inheritance and Variation

     The two principles I wish to begin with are those which are least doubted, by both experience and science. By inheritance, or heredity, it should be understood that I am speaking of the occurrence when offspring resemble to a great degree their parents. To quote Charles Darwin, "No breeder doubts how strong is the tendency to inheritance; that like produces like is his fundamental belief: doubts have been thrown on this principle only by theoretical writers." [*2] By variation, or diversity (or, sometimes even, "mutations"), by this it should be understood that I am speaking of the changes that occur between offspring and parents, that sometimes a child will resemble in all degrees their parents except for some small, almost unnoticeable parts. Again, to quote Charles Darwin, "No one supposes that all the individuals of the same species are cast in the same actual mould." [*3]

     It may almost seem that these principles are in direct adversity to each other. The first concludes that children will be similar to their parents yet the second concludes that children will differ from their parents. To explain what may almost appear as a contradiction, the fact is that organisms will resemble their parents to a degree and they differ from their parents in a degree. Some will greatly resemble their progenitors whereas others will look almost monstrous comparably. As far as proving the truth of inheritance and variation, simple experience would seem to prove it quite easily. For instance, when two members of the same human race decide to have a child, it will be of their race, just as when two people who are tall have a child, their child will also tend to be tall. Yet these are very vague and simple correlations between adults and children. Anyone who has a family will easily be able to conclude that children resemble their parents in great degrees, in facial features, in physical strengths and weaknesses, in body frame, and in other manners. Also, too, no parent will be ably to deny the principle of variation any more than they can deny the principle of inheritance. Those who have children will no doubt see that there is some variation, some degree of difference between them. That there are some attributes held in their child, which neither parent had, is undeniable.

     Though it is quite true that simple experience alone would be enough to sustain belief in both inheritance and variation, I would still like to draw some scientific examples. There was one instance where a man could use the muscles in his scalp to move heavy objects, and even move a set of heavy books. A distant cousin of this man had moved to France, where he was contacted and asked if he possessed the same ability -- and indeed, he did. [*4] It has been proven that genius, as well as insanity and deteriorated mental abilities, often times will run in a family. [*5] For many recreational drugs, which at some times are believed to induce psychological trauma, it is suggested that they should be avoided if there is any family history of schizophrenia or other mental illness. [*6] The ability to produce twins has also been associated with certain families. [*7]

     In regards to variation, there is a type of plant known as "Sporting Plants," which under domestication, are very likely to produce a widely different character in their descendants [*8] To quote Charles Darwin, "At long intervals of time, out of millions of individuals reared in the same country and fed on nearly the same food, deviations of structure so strongly pronounced as to deserve to be called monstrosities arise." [*9] When animals have been observed to breed in captivity (which is a rarity in itself), it has been noticed that the offspring are somewhat unlike their parents. [*10] The scientist, Mr. Walsh, when examining insects, found that insects of the same species often produce secretions, which differ in color, size and nature. [*11] Though somewhat more a piece of evidence from experience, it has been observed, as Darwin wrote, "No two individuals of the same race are quite alike. We may compare millions of faces, and each will be distinct." [*12] In an investigation of the military, it was found that it was an extremely rare instance to find two soldiers with legs that had identical lengths. [*13] Though there are certain trends in how the human skull is developed, some more rounded and others more elongated, Naturalists have confirmed that skulls from the members of the same race will often differ with great variation, even when comparing the skulls of inhabitants of a confined area, such as the Sandwich Islands. [*14] It has been observed that the chief arteries that run through the body differ immensely from individual to individual. [*15] Teeth are so varied from individual to individual, that they have often been used as a means of identification. [*16] It is well known that the feet muscles are not the same in any two out of fifty humans. [*17] The !Kung of Kalahari, a tribe of aboriginals sometimes referred to as "Bushmen," are known to be able to identify individual members of game by their tracks. If a hunter loses the track of his prey, and finds more tracks, they will be able to identify that it is their prey and not another animal. So, too, a child in this tribe can identify their mother's footprints specifically, even when there are numerous prints of other person's around. To these tribesmen, every footprint is identical when compared with the footprints of others. [*18] In thirty six individuals, there were 295 variations in muscles when compared to standard biology textbooks, and in another set of individuals, there were 558 variations. A single body presented 25 distinct abnormalities. [*19] Professor Macalister describes no less than twenty distinct variations in the muscle known as palmaris accesorius. [*20] The famous anatomist Wolff insists that variation of the liver, kidneys, and lungs of the human are great. [*21] The naturalist Brehme has observed that in his tamed monkeys of Africa, no two are alike in disposition and temper, and this is partly innate and partly the result of the manner in which they were educated. [*22] The muscles of our hands and feet, like those of other primates and lower animals, are highly apt to variation. [*23]

     The question of inheritance and variation are of no doubt, both in regard to personal experience and to scientific inquiry. Any person with a family will be able to verify it, just as any educated scientist will come to similar conclusions. What is observed by a father, as he notices his son's height being close to his, is not entirely different when a scientist observes that the ability to produce twins is hereditary. Similarly, when a couple of parents notice that the color of their child's hair is different than both of theirs, it is not much different than when a naturalist discovers hundreds of varieties of muscle development in humans. Essentially, the rest of this work will be written as though the principle of inheritance and variation, as above described, are true. In ending this section, I will quote Charles Darwin on the subject of inheritance and variation...

As a single bud out of the many thousands, produced year after year on the same tree under uniform conditions, has been known suddenly to assume a new character; and as buds on distinct trees, growing under different conditions, have sometimes yielded nearly the same variety- for instance, buds on peach-trees producing nectarines, and buds on common roses producing moss-roses- we clearly see that the nature of the conditions is of subordinate importance in comparison with the nature of the organism in determining each particular form of variation; [*24]

Section II: Adaptations

     Aside from inheritance and variation, there is one other belief that is not disputed among those familiar with the natural world. This belief is that animals in the natural world are remarkably well adaptated to their natural environments. Among even those who diverge from the theory of Evolution, this is hardly doubted. It would take only a very small examination of natural organisms to see that they are quite fit their habitats. The question which may arise among naturalists, though, is not if this is true or not, but why this is true -- at least, this may have been a cause for argument in the nineteenth century, when Darwin first made his proposal of Natural Selection. In this section, I shall briefly expand upon the idea that animals are well fit to the environments in which they live.

     The amphibians and reptiles, closely related phylums of the animal kingdom, are very well fit to their environments, an attribute which does not widely differ from other organisms. The frog, for example, is covered with a skin that helps regulate temperature, water content, and respiration, accompanied by legs which are remarkable at jumping to avoid predators. [*25] The newt has well developed eyes and is capable of regrowing lost limbs. [*26] The salamander's skin secretes a protective, milky poison, which is harmless to humans, and in times of severe drought, they are known to burrow into the earth to avoid dehydration. [*27] A relative of the frog, the toad's warty skin helps regulate moisture, and they are known to secrete poisonous or irritating substances from their skins when threatened by a predator. [*28] The crocodile, perhaps the most famous example of the reptile phylum, has a fleshy valve at the back of its mouth to prevent water from going into the air passages, and its webbed feet -- a trait which many other aquatic animals have -- aids in swimming. [*29] Most lizards have been observed to change color to allow them to blend in with the current environment, thus avoiding predators; some lizards have teeth on the roof of their mouth to aid in hunting, while all lizards have scaly armor for protection. [*30] Related to the lizard is the snake, which also has scaled protection; some snakes carry a poisonous venom to help neutralize prey or fend off predators, while every snake has elastic ligaments connecting the jaw to the skull, thus allowing consuming larger animals whole. [*31] The defense of the turtle is obvious: it's shell, and it is well known that, though it has no teeth, the edges of the jaw are sharp for cutting food. [*32]

     Birds are also noted as being well fit to their environments, especially with the aid of flight, which is sometimes absent in certain species. The gull has webbed feet to help in aquatic movement and long narrow wings that allow for the unsurpassed ability to soar. [*33] The ostrich, though devoid of the ability to fly, has long tough toenails, which it is sometimes known to defend itself with when fleeing is unsuccessful, and they have a keen sight for spotting potential predators. [*34] The owl is a superb predator, with a keen vision and hearing that make it lethal to lower animals. [*35] The pelican has webbed feet, which it uses for running on water to gain acceleration so that it can fly with its bulky frame, and it uses its huge beak to capture fish and other animals living in water. [*36] One of the most talked of birds, in regards to the theory of Evolution and Natural Selection, is the woodpecker. There is ample reason for this. The woodpecker's first and fourth towards are backward, whereas the second and third toes are forward, allowing it a firm grip on tree branches, and giving it the ability to scale trees fairly quickly. Since it's appetite is mostly insects living in trees, it has a hard bill fitted for tear off bark and a powerful neck for hammering. Its tongue is sticky and barbed, which allows it to ensnare insects. [*37]

     The case of mammals having a great deal of advantages should not come to any surprise to an well-observed naturalist. In a very real way, higher mammals mark the yet most advanced organism of this planet: the human. The elephant is equipped with a long trunk to aid in getting water and manipulating the physical world, as well as a thick skin for protection. [*38] The giraffe is the tallest living animal, the length aiding in reaching high up for food; accompanying this length, the giraffe also has an exemplary vision, helping the creature to see predators and enemies from afar. [*39] The kangaroo has powerful hind legs for traveling quickly, and with this the animal also has a pouch for carrying the young, as well as a sacculated (chambered) stomach, which will keep moisture in the body when there is a drought -- a serious threat in an environment like Australia where rainfall is unpredictable. [*40] The koala bear has opposable digits, which allow it to grasp tree branches better, and when extremely young, it attaches to the teets of its mother, and it cannot be removed except with a forceful blow. [*41] An African king, the lion has an adequately developed sight and smell, which aids it when it hunts at night. Also, the lion has powerful forelimbs, which allow it to tackle prey double its size, as well as strong jaw muscles, capable of breaking the vertebrae of its prey. [*42] The tiger, a relative of the lion, has well developed legs, allowing it to leap thirty feet on to prey, and it is outfitted with canine teeth for tearing flesh. [*43]

     Finally, we come to the case of fish, organisms which dominate the largest size of habitat: the oceans. The catfish, which inhabits ponds, builds nests to protect the unborn, and it in certain species, they are known to walk from pond to pond, in search of food. [*44] The eel has dorsal and anal fins which aid in transportation. [*45] Though the term "minnow" has been used loosely to define any fish smaller than a man's finger, this is not the scientifically recognized definition. One of the species of minnow is known to have teeth, specifically used to scraping stones off of food. [*46] The sting ray is equipped with a poisonous sting for attacking prey, and with encounters with humans, it is usually described as extremely painful and there are cases where it proves lethal. [*47] The swordfish is the fastest fish in all of the oceans, and this would definitely serve as an advantage to this predator. Furthermore, it uses its sword to spear its prey. [*48]

     The single purpose of this section was to demonstrate that animals are fit to their environment. It was not my intention to argue that they were perfectly adaptated to where they are living. How is it that the state of organic organisms of our world today have reached their highly adaptive form of today? The question of how has been of much speculation for centuries, but science seems to have come to rest at this point, with the satisfying conclusion of Evolution. There is still the theory of Creationism, that argues that organisms of our world today are perfect due to the idea of an omnipotent god creating them, whereas scientists argue that Evolution through Natural Selection seems like a better view of the problem. Some have argued that the weakest part of the theory of Evolution is that all organic beings are considered imperfect, or, to quote Charles Darwin, "...a distinguished German naturalist has asserted that the weakest part of my theory is, that I consider all organic beings as imperfect: what I have really said is, that all are not as perfect as they might have been in relation to their conditions; and this is shown to be the case by so many native forms in many quarters of the world having yielded their places to intruding foreigners." [*49] To quote Darwin, again...

....cases could be given of introduced plants which have become common throughout whole islands in a period of less than ten years. Several of the plants, such as the cardoon and a tall thistle, which are now the commonest over the whole plains of La Plata, clothing square leagues of surface almost to the exclusion of every other plant, have been introduced from Europe; and there are plants which now range in India, as I hear from Dr. Falconer, from Cape Comorin to the Himalaya, which have been imported from America since its discovery. [*50]

Section III: Natural Selection

     In the previous two sections, I dealt with concepts which I will hereafter deal as fact. The first section dealt with inheritance and variation, how offspring often times resemble their progenitors, though differ in varying degrees. The second section, previously covered, deals with how organisms are adaptated to this world imperfectly, but fit enough to survive and reproduce. Finally, next there comes a sort of theory to bind these two sections. The theory of Natural Selection attempts to explain how organisms came about. To quote Charles Darwin...

Owing to this struggle, variations, however slight and from whatever cause proceeding, if they be in any degree profitable to the individuals of a species, in their infinitely complex relations to other organic beings and to their physical conditions of life, will tend to the preservation of such individuals, and will generally be inherited by the offspring. The offspring, also, will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a small number can survive. I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection, in order to mark its relation to man's power of selection. But the expression often used by Mr. Herbert Spencer of the Survival of the Fittest is more accurate, and is sometimes equally convenient. [*51]

     Simply put, the theory of Natural Selection goes so far as to state that organisms which are fit to survival in their current environment have a better chance to survive. Using some of the examples I had in Section II, consider if a pelican had been born with such a small beak, that it was unable to scoop up any fish from the water? Or, consider for example, if a frog or toad had been born that had skin that was not poisonous to other creatures, or if a woodpecker was born without claws, or if a turtle had been born without a shell? Under the current conditions, if an individual was born with such an attribute, it can be easy to see that they would have lesser chances of surviving. Furthermore, the possibility of variation cannot be denied. In Section I, I demonstrated very compelling evidence that organisms are likely to vary greatly, even if in the most minor or major details. Consider, again, for example, the man who could use his scalp muscles for moving a set of heavy books. In one way, it demonstrates variability, and how humans vary from each other, but in another way, it demonstrates inheritance, as that person's children were also capable of this same ability. Every advantage that an organism has will give it a higher chance of obtaining food and reproducing, thus creating more individuals with like traits -- and of these organisms, the one which has the advantage to the highest degree, will have higher chances of success with mating and survival. So it will continue, organisms breeding and evolving, some species becoming extinct due to the fact that they could no longer compete in their environment, and new beneficial variations occurring To quote Charles Darwin...

It may metaphorically be said that natural selection is daily and hourly scrutinizing, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life. We see nothing of these slow changes in progress, until the hand of time has marked the lapse of ages, and then so imperfect is our view into long-past geological ages, that we see only that the forms of life are now different from what they formerly were. [*52]

     It must be understood clearly, however, that Natural Selection is the theory of well adaptated organisms surviving and reproducing, whereas poorly adaptated organisms will have lower chances of survival and reproduction. There is very little reason not to believe in the validity of such a theory. Even if someone were to find the theory of Evolution as unacceptable, there is no reason why they ought to doubt the theory of Natural Selection, unless such a person is uneducated. However, there is still another theory that often attaches itself to Natural Selection. In several references in Origin of the Species, Darwin referred to it as the Derivative Theory (or, sometimes simply known as "Evolution"): the theory that all higher organisms that exist today evolved from lower organisms through the processes of Natural Selection. There are some who will doubt Evolution while holding the principles of Natural Selection to be fact. The idea of Evolution, though, is simply that the organisms that came about today exist because they formed variations that were successful in their habitats and had offspring with these adaptations, or they evolved. Again, to quote Charles Darwin...

Natural Selection acts exclusively by the preservation and accumulation of variations, which are beneficial under the organic and inorganic conditions to which each creature is exposed at all periods of life. The ultimate result is that each creature tends to become more and more improved in relation to its conditions. This improvement inevitable leads to the gradual advancement of the organisation of the greater number of living beings throughout the world. [*53]

     As we look upon the principles of inheritance and variation, and we look to the natural world and see how organisms are extremely well fit to where they live, it seems only to be a logical deduction that the origin of the species came about through slight variations, each one leaning towards a well-fit end result Before ending this section, I will quote Darwin again in regards to Natural Selection...

The formation of different languages and of distinct species, and the proofs that both have been developed through a gradual process, are curiously parallel. But we can trace the formation of many words further back than that of species, for we can perceive how they actually arose from the imitation of various sounds. We find in distinct languages striking homologies due to community of descent, and analogies due to a similar process of formation. The manner in which certain letters or sounds change when others change is very like correlated growth. We have in both cases the re-duplication of parts, the effects of long-continued use, and so forth. The frequent presence of rudiments, both in languages and in species, is still more remarkable. The letter m in the word am, means I; so that in the expression I am, a superfluous and useless rudiment has been retained. In the spelling also of words, letters often remain as the rudiments of ancient forms of pronunciation. Languages, like organic beings, can be classed in groups under groups; and they can be classed either naturally according to descent, or artificially by other characters. Dominant languages and dialects spread widely, and lead to the gradual extinction of other tongues. A language, like a species, when once extinct, never, as Sir C. Lyell remarks, reappears. The same language never has two birth-places. Distinct languages may be crossed or blended together. We see variability in every tongue, and new words are continually cropping up; but as there is a limit to the powers of the memory, single words, like whole languages, gradually become extinct. As Max Muller has well remarked:- "A struggle for life is constantly going on amongst the words and grammatical forms in each language. The better, the shorter, the easier forms are constantly gaining the upper hand, and they owe their success to their own inherent virtue." To these more important causes of the survival of certain words, mere novelty and fashion may be added; for there is in the mind of man a strong love for slight changes in all things. The survival or preservation of certain favoured words in the struggle for existence is natural selection. [*54]

Section IV: A Note on Further Chapters

     The purpose of this chapter was to lay out some fundamental principles that were necessary to explaining, and then proving, the theory of Evolution, namely the principles of inheritance, variation, the well-fit nature of organisms today, and the theory of Natural Selection. I cannot ask anyone to believe that the species of the world today is due to a long chain of variations and alterations which eventually led to the creation of where we are now. So far, such an assertion would be rather speculative, though logical. At least, it would seem logical to make such a conclusion, but we have no evidence. The following chapters shall deal with the evidence of Evolution. While studying and researching the works of Naturalists, I found an overwhelming amount of evidence. However, the evidence seemed a great deal jumbled, or at least, unorganized. In the following chapters, I will try to demonstrate the evidence for the Derivative Theory in an organized manner. The evidences I have for Evolution are as follows: results of Selective Breeding in domestic organisms, similarities occurring in different organisms, reversionary organs, and vestigial organs. Each piece of evidence is a part of what I would call Interrelation: the theory that all organisms are related to each other in some way. Vestigial organs, sometimes called "rudiments" or "rudimentary organs," are organs which serve no purpose to an organism, yet would have served as a purpose to a life form in a previous state, such as a progenitor evolving into the new state and remnants of the older species are still found in the new one. Reversionary organs -- when appearing known simply as "reversion" -- are organs which are vestigial, yet unlike vestigial organs, they differ in that they only appear in some individuals of a species. To quote Charles Darwin, "These several reversionary structures, as well as the strictly rudimentary ones, reveal the descent of man from some lower form in an unmistakable manner." [*55] When vestigial or reversionary organs appear in a being, they are often underdeveloped, to the point where even if they once serve a purpose, today they do not. There is an Evolutionary shift towards beings without any useless organs, but this shift is not as strong as the one away from injurious organs or the shift towards beneficial ones. The reason why it would be of use for an organism to not have useless appendages is, as Darwin once wrote, "If under changed conditions of life a structure, before useful, becomes less useful, its diminution will be favoured, for it will profit the individual not to have its nutriment wasted in building up an useless structure." [*56]

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