The Descent (The Primitive Earth Book 1)

The experiments showed that simple organic compounds of building blocks of proteins and other macromolecules can be formed from gases with the addition of energy. This experiment inspired many others. His experiment produced a large amount of adenine, the molecules of which were formed from 5 molecules of HCN. There also had been similar electric discharge experiments related to the origin of life contemporaneous with Miller—Urey. MacNevin was passing , volt sparks through methane and water vapor and produced "resinous solids" that were "too complex for analysis.

It is not clear if he ever published any of these results in the primary scientific literature. Wilde submitted a paper to Science on December 15, , before Miller submitted his paper to the same journal on February 10, Wilde's paper was published on July 10, He observed only small amounts of carbon dioxide reduction to carbon monoxide, and no other significant reduction products or newly formed carbon compounds.

Other researchers were studying UV - photolysis of water vapor with carbon monoxide. They have found that various alcohols, aldehydes and organic acids were synthesized in reaction mixture. However, Bada noted that in current models of early Earth conditions, carbon dioxide and nitrogen N 2 create nitrites , which destroy amino acids as fast as they form. When Bada performed the Miller-type experiment with the addition of iron and carbonate minerals, the products were rich in amino acids.

This suggests the origin of significant amounts of amino acids may have occurred on Earth even with an atmosphere containing carbon dioxide and nitrogen.

The Descent of Man (Darwin)/Chapter V - Wikisource, the free online library

Some evidence suggests that Earth's original atmosphere might have contained fewer of the reducing molecules than was thought at the time of the Miller—Urey experiment. There is abundant evidence of major volcanic eruptions 4 billion years ago, which would have released carbon dioxide, nitrogen, hydrogen sulfide H 2 S , and sulfur dioxide SO 2 into the atmosphere. The experiment created a mixture that was racemic containing both L and D enantiomers and experiments since have shown that "in the lab the two versions are equally likely to appear"; [23] however, in nature, L amino acids dominate.

Later experiments have confirmed disproportionate amounts of L or D oriented enantiomers are possible. Originally it was thought that the primitive secondary atmosphere contained mostly ammonia and methane. However, it is likely that most of the atmospheric carbon was CO 2 with perhaps some CO and the nitrogen mostly N 2. The hydrogen atoms come mostly from water vapor. In fact, in order to generate aromatic amino acids under primitive earth conditions it is necessary to use less hydrogen-rich gaseous mixtures.

Most of the natural amino acids, hydroxyacids , purines, pyrimidines, and sugars have been made in variants of the Miller experiment. More recent results may question these conclusions. The University of Waterloo and University of Colorado conducted simulations in that indicated that the early atmosphere of Earth could have contained up to 40 percent hydrogen—implying a much more hospitable environment for the formation of prebiotic organic molecules. The escape of hydrogen from Earth's atmosphere into space may have occurred at only one percent of the rate previously believed based on revised estimates of the upper atmosphere's temperature.

I think this study makes the experiments by Miller and others relevant again. In contrast to the general notion of early earth's reducing atmosphere, researchers at the Rensselaer Polytechnic Institute in New York reported the possibility of oxygen available around 4. Their study reported in on the assessment of Hadean zircons from the earth's interior magma indicated the presence of oxygen traces similar to modern-day lavas.

Conditions similar to those of the Miller—Urey experiments are present in other regions of the solar system , often substituting ultraviolet light for lightning as the energy source for chemical reactions. Comets and other icy outer-solar-system bodies are thought to contain large amounts of complex carbon compounds such as tholins formed by these processes, darkening surfaces of these bodies.

In recent years, studies have been made of the amino acid composition of the products of "old" areas in "old" genes, defined as those that are found to be common to organisms from several widely separated species , assumed to share only the last universal ancestor LUA of all extant species. These studies found that the products of these areas are enriched in those amino acids that are also most readily produced in the Miller—Urey experiment. This suggests that the original genetic code was based on a smaller number of amino acids — only those available in prebiotic nature — than the current one.

Jeffrey Bada , himself Miller's student, inherited the original equipment from the experiment when Miller died in Based on sealed vials from the original experiment, scientists have been able to show that although successful, Miller was never able to find out, with the equipment available to him, the full extent of the experiment's success. Later researchers have been able to isolate even more different amino acids, 25 altogether. Bada has estimated that more accurate measurements could easily bring out 30 or 40 more amino acids in very low concentrations, but the researchers have since discontinued the testing.

Miller's experiment was therefore a remarkable success at synthesizing complex organic molecules from simpler chemicals, considering that all life uses just 20 different amino acids. In , a group of scientists examined 11 vials left over from Miller's experiments of the early s. In addition to the classic experiment, reminiscent of Charles Darwin 's envisioned "warm little pond", Miller had also performed more experiments, including one with conditions similar to those of volcanic eruptions.

This experiment had a nozzle spraying a jet of steam at the spark discharge. By using high-performance liquid chromatography and mass spectrometry , the group found more organic molecules than Miller had. They found that the volcano-like experiment had produced the most organic molecules, 22 amino acids, 5 amines and many hydroxylated molecules, which could have been formed by hydroxyl radicals produced by the electrified steam. The group suggested that volcanic island systems became rich in organic molecules in this way, and that the presence of carbonyl sulfide there could have helped these molecules form peptides.

The main problem of theories based around amino acids is the difficulty in obtaining spontaneous formation of peptides. Since John Desmond Bernal 's suggestion that clay surfaces could have played a role in abiogenesis [38] , scientific efforts have been dedicated to investigating clay-mediated peptide bond formation, with limited success.

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Peptides formed remained over-protected and shown no evidence of inheritance or metabolism. In December a theoretical model developed by Erastova and collaborators [39] [40] suggested that peptides could form at the interlayers of layered double hydroxides such as green rust in early earth conditions. According to the model, drying of the intercalated layered material should provide energy and co-alignment required for peptide bond formation in a ribosome -like fashion, while re-wetting should allow mobilising the newly formed peptides and repopulate the interlayer with new amino acids.

Researches also observed slightly different adsorption preferences for different amino acids, and postulated that, if coupled to a diluted solution of mixed amino acids, such preferences could lead to sequencing.

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In October , researchers at McMaster University on behalf of the Origins Institute announced the development of a new technology, called a Planet Simulator , to help study the origin of life on planet Earth and beyond. Below is a table of amino acids produced and identified in the "classic" experiment, as published by Miller in , [4] the re-analysis of vials from the volcanic spark discharge experiment, [45] and the re-analysis of vials from the H 2 S-rich spark discharge experiment. From Wikipedia, the free encyclopedia. Chemical synthesis of amino acids.

Origins of Life and Evolution of the Biosphere. Archived from the original PDF on February 27, Archived PDF from the original on Miller states that he made "A more complete analysis of the products" in the experiment, listing additional results. It is extremely doubtful whether the offspring of the more sympathetic and benevolent parents, or of those who were the most faithful to their comrades, would be reared in greater numbers than the children of selfish and treacherous parents belonging to the same tribe.

He who was ready to sacrifice his life, as many a savage has been, rather than betray his comrades, would often leave no offspring to inherit his noble nature. The bravest men, who were always willing to come to the front in war, and who freely risked their lives for others, would on an average perish in larger numbers than other men. Therefore, it hardly seems probable that the number of men gifted with such virtues, or that the standard of their excellence, could be increased through natural selection, that is, by the survival of the fittest; for we are not here speaking of one tribe being victorious over another.

Although the circumstances, leading to an increase in the number of those thus endowed within the same tribe, are too complex to be clearly followed out, we can trace some of the probable steps. In the first place, as the reasoning powers and foresight of the members became improved, each man would soon learn that if he aided his fellow-men, he would commonly receive aid in return. From this low motive he might acquire the habit of aiding his fellows; and the habit of performing benevolent actions certainly strengthens the feeling of sympathy which gives the first impulse to benevolent actions.

Habits, moreover, followed during many generations probably tend to be inherited. But another and much more powerful stimulus to the development of the social virtues, is afforded by the praise and the blame of our fellow-men. To the instinct of sympathy, as we have already seen, it is primarily due, that we habitually bestow both praises and blame on others, whilst we love the former and dread the latter when applied to ourselves; and this instinct no doubt was originally acquired, like all the other social instincts, through natural selection.

At how early a period the progenitors of man in the course of their development, became capable of feeling and being impelled by, the praise or blame of their fellow-creatures, we cannot of course say. But it appears that even dogs appreciate encouragement, praise, and blame. The rudest savages feel the sentiment of glory, as they clearly show by preserving the trophies of their prowess, by their habit of excessive boasting, and even by the extreme care which they take of their personal appearance and decorations; for unless they regarded the opinion of their comrades, such habits would be senseless.

They certainly feel shame at the breach of some of their lesser rules, and apparently remorse, as shewn by the case of the Australian who grew thin and could not rest from having delayed to murder some other woman, so as to propitiate his dead wife's spirit. Though I have not met with any other recorded case, it is scarcely credible that a savage, who will sacrifice his life rather than betray his tribe, or one who will deliver himself up as a prisoner rather than break his parole, [6] would not feel remorse in his inmost soul, if he had failed in a duty, which he held sacred.

We may therefore conclude that primeval man, at a very remote period, was influenced by the praise and blame of his fellows. It is obvious, that the members of the same tribe would approve of conduct which appeared to them to be for the general good, and would reprobate that which appeared evil. To do good unto others—to do unto others as ye would they should do unto you—is the foundation-stone of morality. It is, therefore, hardly possible to exaggerate the importance during rude times of the love of praise and the dread of blame. A man who was not impelled by any deep, instinctive feeling, to sacrifice his life for the good of others, yet was roused to such actions by a sense of glory, would by his example excite the same wish for glory in other men, and would strengthen by exercise the noble feeling of admiration.

He might thus do far more good to his tribe than by begetting offspring with a tendency to inherit his own high character. I need not, however, repeat what I have said on this head in the fourth chapter. Ultimately our moral sense or conscience becomes a highly complex sentiment—originating in the social instincts, largely guided by the approbation of our fellow-men, ruled by reason, self-interest, and in later times by deep religious feelings, and confirmed by instruction and habit.

It must not be forgotten that although a high standard of morality gives but a slight or no advantage to each individual man and his children over the other men of the same tribe, yet that an increase in the number of well-endowed men and an advancement in the standard of morality will certainly give an immense advantage to one tribe over another. A tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage, and sympathy, were always ready to aid one another, and to sacrifice themselves for the common good, would be victorious over most other tribes; and this would be natural selection.

At all times throughout the world tribes have supplanted other tribes; and as morality is one important element in their success, the standard of morality and the number of well-endowed men will thus everywhere tend to rise and increase. It is, however, very difficult to form any judgment why one particular tribe and not another has been successful and has risen in the scale of civilisation. Many savages are in the same condition as when first discovered several centuries ago. Bagehot has remarked, we are apt to look at the progress as normal in human society; but history refutes this.

The ancients did not even entertain the idea, nor do the Oriental nations at the present day. According to another high authority, Sir Henry Maine [7] , "the greatest part of mankind has never shewn a particle of desire that its civil institutions should be improved. But it has often been remarked, that a cool climate, from leading to industry and to the various arts, has been highly favourable thereto. The Esquimaux, pressed by hard necessity, have succeeded in many ingenious inventions, but their climate has been too severe for continued progress.

The Descent of Man (Darwin)/Chapter V

Nomadic habits, whether over wide plains, or through the dense forests of the tropics, or along the shores of the sea, have in every case been highly detrimental. Whilst observing the barbarous inhabitants of Tierra del Fuego, it struck me that the possession of some property, a fixed abode, and the union of many families under a chief, were the indispensable requisites for civilisation.

Such habits almost necessitate the cultivation of the ground; and the first steps in cultivation would probably result, as I have elsewhere shewn, [8] from some such accident as the seeds of a fruit-tree falling on a heap of refuse, and producing an unusually fine variety. The problem, however, of the first advance of savages towards civilisation is at present much too difficult to be solved.

Natural Selection as affecting Civilised Nations. But some remarks on the action of natural selection on civilised nations may be worth adding. This subject has been ably discussed by Mr. Greg, [9] and previously by Mr. With savages, the weak in body or mind are soon eliminated; and those that survive commonly exhibit a vigorous state of health. We civilised men, on the other hand, do our utmost to check the process of elimination; we build asylums for the imbecile, the maimed, and the sick; we institute poor-laws; and our medical men exert their utmost skill to save the life of every one to the last moment.

There is reason to believe that vaccination has preserved thousands, who from a weak constitution would formerly have succumbed to small-pox. Thus the weak members of civilised societies propagate their kind. No one who has attended to the breeding of domestic animals will doubt that this must be highly injurious to the race of man. It is surprising how soon a want of care, or care wrongly directed, leads to the degeneration of a domestic race; but excepting in the case of man himself, hardly any one is so ignorant as to allow his worst animals to breed.

The aid which we feel impelled to give to the helpless is mainly an incidental result of the instinct of sympathy, which was originally acquired as part of the social instincts, but subsequently rendered, in the manner previously indicated, more tender and more widely diffused.

Nor could we check our sympathy, even at the urging of hard reason, without deterioration in the noblest part of our nature.

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• Miller–Urey experiment - Wikipedia?

The surgeon may harden himself whilst performing an operation, for he knows that he is acting for the good of his patient; but if we were intentionally to neglect the weak and helpless, it could only be for a contingent benefit, with an overwhelming present evil. We must therefore bear the undoubtedly bad effects of the weak surviving and propagating their kind; but there appears to be at least one check in steady action, namely that the weaker and inferior members of society do not marry so freely as the sound; and this check might be indefinitely increased by the weak in body or mind refraining from marriage, though this is more to be hoped for than expected.

In every country in which a large standing army is kept up, the finest young men are taken by the conscription or are enlisted. They are thus exposed to early death during war, are often tempted into vice, and are prevented from marrying during the prime of life. On the other hand the shorter and feebler men, with poor constitutions, are left at home, and consequently have a much better chance of marrying and propagating their kind. Man accumulates property and bequeaths it to his children, so that the children of the rich have an advantage over the poor in the race for success, independently of bodily or mental superiority.

On the other hand, the children of parents who are short-lived, and are therefore on an average deficient in health and vigour, come into their property sooner than other children, and will be likely to marry earlier, and leave a larger number of offspring to inherit their inferior constitutions. But the inheritance of property by itself is very far from an evil; for without the accumulation of capital the arts could not progress; and it is chiefly through their power that the civilised races have extended, and are now everywhere extending their range, so as to take the place of the lower races.

Nor does the moderate accumulation of wealth interfere with the process of selection. When a poor man becomes moderately rich, his children enter trades or professions in which there is struggle enough, so that the able in body and mind succeed best. The presence of a body of well-instructed men, who have not to labour for their daily bread, is important to a degree which cannot be over-estimated; as all high intellectual work is carried on by them, and on such work, material progress of all kinds mainly depends, not to mention other and higher advantages.

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No doubt wealth when very great tends to convert men into useless drones, but their number is never large; and some degree of elimination here occurs, for we daily see rich men, who happen to be fools or profligate, squandering away their wealth. Primogeniture with entailed estates is a more direct evil, though it may formerly have been a great advantage by the creation of a dominant class, and any government is better than none. Most eldest sons, though they may be weak in body or mind, marry, whilst the younger sons, however superior in these respects, do not so generally marry.

Nor can worthless eldest sons with entailed estates squander their wealth. But here, as elsewhere, the relations of civilised life are so complex that some compensatory checks intervene. The men who are rich through primogeniture are able to select generation after generation the more beautiful and charming women; and these must generally be healthy in body and active in mind. The evil consequences, such as they may be, of the continued preservation of the same line of descent, without any selection, are checked by men of rank always wishing to increase their wealth and power; and this they effect by marrying heiresses.

But the daughters of parents who have produced single children, are themselves, as Mr. Galton [12] has shewn, apt to be sterile; and thus noble families are continually cut off in the direct line, and their wealth flows into some side channel; but unfortunately this channel is not determined by superiority of any kind. Although civilisation thus checks in many ways the action of natural selection, it apparently favours the better development of the body, by means of good food and the freedom from occasional hardships.

Miller–Urey experiment

This may be inferred from civilised men having been found, wherever compared, to be physically stronger than savages. Even the great luxury of the rich can be but little detrimental; for the expectation of life of our aristocracy, at all ages and of both sexes, is very little inferior to that of healthy English lives in the lower classes.

We will now look to the intellectual faculties. If in each grade of society the members were divided into two equal bodies, the one including the intellectually superior and the other the inferior, there can be little doubt that the former would succeed best in all occupations, and rear a greater number of children. Even in the lowest walks of life, skill and ability must be of some advantage; though in many occupations, owing to the great division of labour, a very small one.

Hence in civilised nations there will be some tendency to an increase both in the number and in the standard of the intellectually able. But I do not wish to assert that this tendency may not be more than counterbalanced in other ways, as by the multiplication of the reckless and improvident; but even to such as these, ability must be some advantage. It has often been objected to views like the foregoing, that the most eminent men who have ever lived have left no offspring to inherit their great intellect.

Galton says, [15] "I regret I am unable to solve the simple question whether, and how far, men and women who are prodigies of genius are infertile. I have, however, shewn that men of eminence are by no means so. In the case of corporeal structures, it is the selection of the slightly better-endowed and the elimination of the slightly less well-endowed individuals, and not the preservation of strongly-marked and rare anomalies, that leads to the advancement of a species.

When in any nation the standard of intellect and the number of intellectual men have increased, we may expect from the law of the deviation from an average, that prodigies of genius will, as shewn by Mr. Galton, appear somewhat more frequently than before. In regard to the moral qualities, some elimination of the worst dispositions is always in progress even in the most civilised nations. Malefactors are executed, or imprisoned for long periods, so that they cannot freely transmit their bad qualities. Melancholic and insane persons are confined, or commit suicide.

Violent and quarrelsome men often come to a bloody end. The restless who will not follow any steady occupation—and this relic of barbarism is a great check to civilisation [17] —emigrate to newly-settled countries, where they prove useful pioneers. Intemperance is so highly destructive, that the expectation of life of the intemperate, at the age of thirty for instance, is only In the breeding of domestic animals, the elimination of those individuals, though few in number, which are in any marked manner inferior, is by no means an unimportant element towards success.

This especially holds good with injurious characters which tend to reappear through reversion, such as blackness in sheep; and with mankind some of the worst dispositions, which occasionally without any assignable cause make their appearance in families, may perhaps be reversions to a savage state, from which we are not removed by very many generations. This view seems indeed recognised in the common expression that such men are the black sheep of the family.

With civilised nations, as far as an advanced standard of morality, and an increased number of fairly good men are concerned, natural selection apparently effects but little; though the fundamental social instincts were originally thus gained. But I have already said enough, whilst treating of the lower races, on the causes which lead to the advance of morality, namely, the approbation of our fellow-men—the strengthening of our sympathies by habit—example and imitation—reason—experience, and even self-interest—instruction during youth, and religious feelings. A most important obstacle in civilised countries to an increase in the number of men of a superior class has been strongly insisted on by Mr.

Galton, [19] namely, the fact that the very poor and reckless, who are often degraded by vice, almost invariably marry early, whilst the careful and frugal, who are generally otherwise virtuous, marry late in life, so that they may be able to support themselves and their children in comfort. Those who marry early produce within a given period not only a greater number of generations, but, as shewn by Dr. Duncan, [20] they produce many more children.

The children, moreover, that are borne by mothers during the prime of life are heavier and larger, and therefore probably more vigorous, than those born at other periods. Thus the reckless, degraded, and often vicious members of society, tend to increase at a quicker rate than the provident and generally virtuous members.

Greg puts the case: Given a land originally peopled by a thousand Saxons and a thousand Celts—and in a dozen generations five-sixths of the population would be Celts, but five-sixths of the property, of the power, of the intellect, would belong to the one-sixth of Saxons that remained. In the eternal 'struggle for existence,' it would be the inferior and less favoured race that had prevailed—and prevailed by virtue not of its good qualities but of its faults.

There are, however, some checks to this downward tendency. We have seen that the intemperate suffer from a high rate of mortality, and the extremely profligate leave few offspring. The poorest classes crowd into towns, and it has been proved by Dr. Stark from the statistics of ten years in Scotland, [21] that at all ages the death-rate is higher in towns than in rural districts, "and during the first five years of life the town death-rate is almost exactly double that of the rural districts. With women, marriage at too early an age is highly injurious; for it has been found in France that, "twice as many wives under twenty die in the year, as died out of the same number of the unmarried.

Lastly, if the men who prudently delay marrying until they can bring up their families in comfort, were to select, as they often do, women in the prime of life, the rate of increase in the better class would be only slightly lessened. It was established from an enormous body of statistics, taken during , that the unmarried men throughout France, between the ages of twenty and eighty, die in a much larger proportion than the married: Stark remarks on this, "Bachelorhood is more destructive to life than the most unwholesome trades, or than residence in an unwholesome house or district where there has never been the most distant attempt at sanitary improvement.

Stark seems to have come to the conclusion that marriage in itself is a main cause of prolonged life, from finding that aged married men still have a considerable advantage in this respect over the unmarried of the same advanced age; but every one must have known instances of men, who with weak health during youth did not marry, and yet have survived to old age, though remaining weak, and therefore with a lessened chance of life or of marrying.

There is another remarkable circumstance which seems to support Dr. Stark's conclusion, namely, that widows and widowers in France suffer in comparison with the married a very heavy rate of mortality; but Dr. Farr attributes this to the poverty and evil habits consequent on the disruption of the family, and to grief.

On the whole we may conclude with Dr. Farr that the lesser mortality of married than of unmarried men, which seems to be a general law, "is mainly due to the constant elimination of imperfect types, and to the skilful selection of the finest individuals out of each successive generation;" the selection relating only to the marriage state, and acting on all corporeal, intellectual, and moral qualities. If the various checks specified in the two last paragraphs, and perhaps others as yet unknown, do not prevent the reckless, the vicious and otherwise inferior members of society from increasing at a quicker rate than the better class of men, the nation will retrograde, as has too often occurred in the history of the world.

We must remember that progress is no invariable rule. It is very difficult to say why one civilised nation rises, becomes more powerful, and spreads more widely, than another; or why the same nation progresses more quickly at one time than at another. We can only say that it depends on an increase in the actual number of the population, on the number of men endowed with high intellectual and moral faculties, as well as on their standard of excellence.

Corporeal structure appears to have little influence, except so far as vigour of body leads to vigour of mind. It has been urged by several writers that as high intellectual powers are advantageous to a nation, the old Greeks, who stood some grades higher in intellect than any race that has ever existed, [26] ought, if the power of natural selection were real, to have risen still higher in the scale, increased in number, and stocked the whole of Europe.

Here we have the tacit assumption, so often made with respect to corporeal structures, that there is some innate tendency towards continued development in mind and body. But development of all kinds depends on many concurrent favourable circumstances. Natural selection acts only tentatively.

Individuals and races may have acquired certain indisputable advantages, and yet have perished from failing in other characters. The Greeks may have retrograded from a want of coherence between the many small states, from the small size of their whole country, from the practice of slavery, or from extreme sensuality; for they did not succumb until "they were enervated and corrupt to the very core. Who can positively say why the Spanish nation, so dominant at one time, has been distanced in the race?

The awakening of the nations of Europe from the dark ages is a still more perplexing problem. At that early period, as Mr. Galton has remarked, almost all the men of a gentle nature, those given to meditation or culture of the mind, had no refuge except in the bosom of a Church which demanded celibacy; [28] and this could hardly fail to have had a deteriorating influence on each successive generation.