Evolution is the branch of Biology that refers to all the changes that have originated the diversity of life on Earth, from its beginnings to the present day. Currently, we biologists are convinced, by the accumulated evidences, that all the living beings, humans included arose in the course of the history of the Earth, and that all the organisms were originated from primitive simple forms.
Evolution is a theory by the context of the scientific proofs confirmed by the observation of the evolutionary process in modern communities. It permits that we keep a high degree of certainty about the current presence of the evolutionary mechanisms working on nature, in such form that we should not interpret erroneously the Scientific Process. Only people that do not want it do not see evidence on evolution.
When a statement has not been verified it is called "hypothesis", but if the hypothesis is submitted to experimental tests, and it is verified as certain, then it reaches the level of "Theory".
Evolution depends directly from the genetic laws and it is considered as a principle of order in nature.
THE ORIGIN OF LIFE
Based on the information provided by the Geology, Astronomy and Genetic, biologists can draw a history on the origin of life.
First of all, we should think that Earth did not have the conditions that it has in present-day. Earth was hot, lacked Oxygen and its atmosphere was highly reductive. Earth possessed a dense ringed cloud made by dust, gases and water that was maintained by Earth’s gravitational force and that lately formed the atmosphere, the oceans and the crust of Earth when the dust dropped down on Earth’s surface.
Some four billion years ago, the Earth had an atmosphere saturated with toxic gases (acetylene, ethane, methane, carbon monoxide, carbon dioxide, sulfur dioxide, etc.) and it lacked oxygen. It had a vast amount of water vapor. The atmospheric heat was intense and the Earth was agitated by violent volcanic eruptions.
Our Moon would be seen four times larger than at present day, the giant exterior planets and our moon acted like protective screens against the meteorites (recent reports upon the date of the earliest meteorite bombardment against the system Earth-Moon reveal that it took place 3.9 billion years. Life appeared on Earth one hundred million years after), and the Sun shone dimly. In the tepid water of the oceans the organic compounds were dissolved, forming a "nutritious soup".
At first, many complex organic molecules were synthesized, among them the proteins, the nucleic acids, the lipids and the carbohydrates. Then the prebiotic molecules originated coacervates.
COACERVATE: A coacervate is an aggregate of molecules attached one to another by electrostatic forces. Those molecules are synthesized abiotically.
PROTOBIONT: A. I. Oparin from Russia named coacervates to protobionts. A protobiont, a kind of coacervate, is a steady globule that is apt to self-arrange if a suspension of proteins, polysaccharides and nucleic acids, is agitated. Many macromolecules were enclosed into coacervates. As the first Biomolecules were formed, which were able to self-reproduction, they originated the first cell. As Guanine-Cytosine (G + C) pair in the nucleic acids is not thermo-resistant, we think that the first cells were not originated in a very hot water. At least it was not higher than 70 °F. In order that the biologists can obtain a deep comprehension of the Origin of Life on Earth (from here on, OLE), it is necessary to consider that 3.8 billion years ago the environment was dissimilar to the current environment.
We also know the primary conditions thanks to the analysis of the geological layers. These analyses reveal us a different primitive Earth. This constitutes one of the strongest evidences for the OLE. Of course, life was not generated spontaneously at this time and it was not generated with the diversity we observe now. What's more, as biologists, we do not presuppose that life begun with a non-complex cell, nor with one solitary fragment with the ability of copying itself, but numerous self replicating molecules surrounded by enough food to sustain them in an uninterrupted self replication.
What did this food be composed of? We think that the food contained autocatalytic proteins (among other simple and complex organic molecules as glycosides and lipids). Afterward, many self replicating molecules were eliminated by the variability of the environment. As the environment changed, many molecular configurations were held to spontaneous processes that impelled them to the thermal equilibrium in short periods. (See Abiogenesis for more details)
THE EVOLUTIONARY STRATEGY
THE EVOLUTION OF LIVING BEINGS OCCURS BY THE CONFLUENCE OF THREE DETERMINANT INTERDEPENDENT COMPONENTS:
NATURAL SELECTION- it is the assembly of alterations in the environment of the organisms (can be exerted to an individual or communitarian level), gradually or suddenly, which provoke one particular strain capable to annihilate the less adaptable individuals or species, and doing to prevail the best adaptable. A good example of Natural Selection is the proficiency to perform natatorium movements. Historically, the genes that determine that characteristic were in the genetic pile of that population previous to the occasion to make use of it. Some members of the population possess the genes, while others do not. When a flood occurs, those with the advantageous genes will survive; on the other hand, those unable to execute natatorium movements will perish, because they are deficient in the genes that determine the ability.
NEUTRALITY- this concept refers to the presence of genes that determine new phenotypic characteristics, which accumulate in the genetic pile of the population, without acting like favoring genes in the survival of the individual, nor to contribute to their extermination. An illustration at hand reach is the presence of nipples in mammalian males, which functionality is abolished because males do not breastfeed their infants. However, the gene that determines the development of nipples continues being expressed and being transmitted to the descent.
STRUCTURING- still when a selective pressure on the individuals is not produced, some structural changes occur in them that propitiate a functional advantage upon those that lack of these modifications. In this way, the structural changes that conduct to a variation in the function transfer to the individual toward another evolutionary line, increasing also its ability to occupy other ecological niches, or to be moved among various niches accord with its requisites to survive. An example of Structuring is the straightened up position of humans. Humans did not straighten up by necessity, because the structural change occurred as an event to the chance, not in function of a selective environmental event. When humans' posture was modified, the individuals were before the disjunctive of abandoning their prior ecological niche; the new posture qualified them to inhabit in more open and less limited in resources areas. It did not impede that the individuals could continue inhabiting in their prior ecological niches, so Homo sapiens' world was expanded.
Randomly induced mutations leads typically to an incompetence to survive in a given environment or to survive to changes in the conditions of the environment. Some portions in the Genome are more able to take up the nucleotide sequence, and the way to carry out it is through the recombination of genetic material, based upon the ancestors' history of success. Thus, Biomolecules have the capability to "see" and "select" the most appropriate changes to produce a new function, or the less viable that could cut off something vital.
Genomes encode this strategy, and the organisms have exchanged genetic information through horizontal gene transfer. It is taking place just now, and it will be coming in the future. Biodiversity is a source of genetic information, and the interchanges of information occur among the varied organisms, so it becomes in a good reason to start with the priority in the conservation of the Biodiversity. Is there any determinant factor that favor and direct the evolutionary changes? Yes, there is a determinant factor named Natural Selection. Natural selection is the external and internal assembly of pressures that provoke a stress into a specific community acting upon each individual. The best propitious genes will survive to those pressures, and the less adequate will disappear. But this is not always thus, therefore in many occasions the genes for behavior in group favor also the survival of "weak" beings.
If a being possesses a propitious allele combination, then those alleles will be transmitted to its offspring, in such way that the favorable alleles will appear in a greater proportion in the following generations.
Let me show it by example:
A population of 200 000 ants walk through the forest devouring what they find palatable on their way. Their running conducts them to the border of a stream of water (environmental pressure), which they should cross for continuing their migration. Many of them venture to cross the stream just to be dragged and drowned by water. These ants lack of alleles to determine a behavior of cooperation in-group. Many of them couple their bodies, one after another, forming a bridge on which other ants can cross the stream without difficulty. These ants possess alleles, which determine their behavior in-group and survived (Survival of the best adapted).
Many fertile male ants possessed those alleles and they survived (conservation of genetic variation in populations), so the favorable alleles were added to the Genetic Reservoir's community. Each time more favorable genes will be added, because those, which possess unfavorable genes, will perish because of their incompetence.
From this example we conclude that there is an evolutionary trend toward a uniform distribution. However, the non-favorable alleles still persist in the community because many ants with the defect were able to cross the water on top of the living bridge, and those alleles also persist in the genome of the surviving ants, without expression due to specific molecular stopgap mechanisms. If the surviving ants possessed a new characteristic in their physical aspect (Phenotype), then their anatomical constitution would also change and it would constitute a visible change.
As I am talking on ants, some researchers found that a species of argentinean ants invaded the United States territory. For this case, argentinean ants evolved according to variations of the environmental conditions. At their place of origin, argentinean ants show aggressive intraspecific behavior. They attack one to another, so they cannot establish large colonies and cannot prosper as permanent populations at particular locations.
On the other hand, this behavioral characteristic has been replaced by a behavior of cooperation in-group. Thus, in USA, they build large colonies and they have adapted perfectly to the environment, in such way that many USA's native species have been displaced from their natural habitats by invader ants. The change was determined through modifications in the gene expression.
Many evolutionary changes occur visibly in a short time, as the polymorphism in communities of fenches in Galapagos Island with modified beaks, which were provoked by the hardness of the seeds (Selective Pressure) that they did have to break. The fenches that had the strongest beak survived (Survival of the best adapted). As these had a wider beak than others from the same variety did, then a new anatomical characteristic (Phenotype)- determined by alleles (Genotype) - was manifested in an interim smaller than 30 years.
But it does not always happen like this: Evolutionary Ecologists have shown that the females of some species of mallard are stimulated by the attractiveness of males for determining the strength of their offspring by means of a larger addition of testosterone to their eggs.
CONDITIONS FOR EVOLUTION
Not all changes are evolution. Evolution is a process system which involves variation, reproduction, heritability and selection.
Variation refers to changes of the individual genotype which could or not be expressed in the individual’s phenotype. Evolution is not possible without variation.
Reproduction is a function of living systems which permits the production of new entities which could or not share the genotypic changes of their ancestors. Evidently, evolution is impossible without reproduction.
Heritability is the aptitude of transferring the genetic information from preexisting entities to their offspring. Obviously, biological evolution is unfeasible without Heritability.
Selection is the set of variations in the external or internal medium which provides stress situations for individuals, populations, communities, biota, etc. Evolution can take place without selection by stochastic radiation.
The evolutionary transformation of structures and functions (as well as behavior) of the living beings occurs thanks to long episodes of successful adaptations to unstable environmental conditions and to the continued submission of biosystems to the unbreakable law of Natural Selection.
Current reviews of evolutionary episodes have demonstrated that the process of Evolution may occur in 100,000 years or less, which is considered fast in geological terms. Losos, J.B., Warheit, K.I., Schoener, T.W. described an innovative survey, allowing us to conclude that natural selection may occur in 10 to 14 years by introducing Anolis lizards to islands where those lizards prospered (in the Bahamas) with few or almost null restrictions.
The vegetation in those islands is elevated. Later, the researchers recovered lizards from this initial population and brought them in to other smaller islands in the vicinity where there were not lizards. The difference between both types of islands is the height of the vegetation.
Smaller islands had few trees or lack of trees, and its forests are small and slight. Most of those lizards adapted and flourished. The scientists examined those lizards several years after their relocation and detected some structural changes that developed into most evident changes in 10 to 14 years since the environmental modification. They detected variations in hind limb length that became shorter than the initial length. The evolution of hind appendages length was proportional to the diameter of the thinner plants where the lizards settled on; that is, the thinner the plants, the shorter the hind limb.
EVIDENCES ON EVOLUTION
Biological evolution provides visible evidences that Evolutionists can perceive at whatever time. These are particular evidences that we have carried on whenever we have had to invalidate antiscientific allegations. There are molecular, ecological, fossil, anatomical and embryological evidences. The handiest evidences are the ecological facts because we can observe them at any moment, without the requirement of hanging on through too extended periods.
On the study of Ecology, the observation of the geographical distribution of biological specie is the best evidence on Evolution. Australian fauna would be a good example for this topic. Australia remained geographically isolated from the other continents by oceanic barriers, so there was not a sharing of alleles between foreign populations and the correlated Australian populations. Thanks to the geographic isolation, Australian specie evolved until form a special biodiversity, with species that were not ordinarily found living in the other continents.
Why most mammals in Australia are marsupial mammals? This is because most of the predecessors of the Australian mammals were marsupials; there were few placental ancestors. When Australia was separated from Asiatic continent, the main populations of mammals that remained trapped into the continent were marsupials.
Another example resides on the distribution of monkeys throughout the world. Before the existence of an exchange of flora and fauna between Old World and New World, monkeys with prehensile tails (squirrel monkey, titi, etc.) -except lemurs and tarsiers- only lived in America. Anthropoid apes without prehensile tails (like chimpanzees, gorillas and orangutans) only existed at Old World. Thus, we found that all monkeys in the New World were arboreal, while apes from the Old World can be both ground dwelling and arboreal. This means that evolutionary lines diverged in some special moment in the history of the planet. Most Paleontologists coincide on the separation of the American continent from Pangaea as the cause of the segregation of monkeys' ancestors. The American continent was not as it is at present. South America was separated from North America by oceanic water (about 65 millions of years ago).
I have described above a present-day example on evolution of behavior (Argentinean ants). A better example about the development of the intelligence is found in domesticated chimpanzees. It is extremely unusual that a non-human animal understand the fact of his own existence. If you place your pet before a mirror, he will be deceived for his own reflection, making him to believe that his own image is another individual. If your pet is a dog, probably it will bark against his own image as if the reflection were another dog. It does not happen with chimpanzees, which acknowledge of their existence is pretty unusual. The chimpanzee will recognize the reflection on the mirror as a reflected image of himself and probably the chimpanzee will begin to gesticulate and to show demonstrations of being enjoying with his own image. This new ability is manifested best in chimpanzees born in captivity, but wild chimpanzees can develop the skill if they are placed under the same experimental conditions.
The cryptic coloration is an adaptation of plants and animals to protect themselves from predators, to be imperceptible for preys, or to be attractive for spreaders of pollen, seeds, etc. (it is not mimicry).
A classical example is the ability of the mottled moths (Biston betularia)), which have changed the colors of their body for hiding themselves from predators to simulate the colors of the place where they rest. There are two varieties of mottled moth, a white and a black varieties. The white moths were found only in areas where there were trees with barks covered by light lichens. The first dark moth was detected in areas of trees, which trunks were covered by industrial soot (dark).
H. B. D. Kettlewell set on the mystery when he observed that the clear moths were more visible for birds if they stayed still on dark trunks; on the other hand, dark moths were almost undetectable -even to the human eyes- if they were resting on dark trunks. As industrialization expanded, dark moths prevailed over clear moths in areas near to factories. However, this case of moths is too weak as to be taken seriously because the experiment was manipulated.
At this point, you should know about the world-shattering information on the deciphering of the Human Genome (HG). Many of us have written articles for newspapers referring the importance this landmark has in applied science. We have talked about the importance that the unveiling of HG has for biotechnology and for medical investigation, but few scientists have written about the meaning that it has for basic sciences, specifically for Evolution.
The analysis of the HG reveals things not seen before. The humanity has evolved through millions of years as any living being. We begun as an early bacterium, from which we conserve some genes, then we evolved toward more complex organisms, as sponges, coelenterates, fish, amphibians, reptiles and finally mammalians, conserving the genetic remnants of those life forms attached to our genome. All of this is found in the HG. We can say that we are built in part by bacteria, in part by mushrooms, in part by jellyfish, in part by rodents, etc. Humans have genetic information acquired from other species.
This is an irrefutable substantiation for evolution, and the final demonstration on the falsehood of Creationism. With the deciphering of the HG, it has been shown that the intelligent creation -or intelligent planned evolution- has never existed. However, this compels us to accept with humility that we are not better than the remainder of the species and that we are not the conclusion of evolution, but just one step toward other creatures more advanced than humans. Human beings are merely in transit through a very extensive evolution process as other species. Scientists no longer have to elude criticisms from creationists; therefore the maximum attestation of evolution is located in ourselves, in our genes. Human Genome has been made little by little from the genomes of other species.
Microspheres are minuscule droplets of proteinoids self-combined when organic complexes are mixed with cold water. The protein membranes that cover microspheres are selectively permeable (some resemblance to the cell membrane). Some microspheres are capable to keep energy in form of membrane potential (voltage transversely to the membrane).
Protobionts are considered the first microspheres that acquired a greater molecular complexity towards the formation of cells, that is to say, the coacervates that evolved to cells (protos = first, bios = life). Most of the modern biologists prefer to talk about "protobionts" instead "proto-cells", because protobionts are considered the biochemical precursors of living cells.
STEP BY STEP EXPLANATION OF ABIOGENESIS ON EARTH
Based on the physical and chemical laws that rule the cosmos, we infer that life is a thermal possibility in the Universe.
The elements are produced in the new generating stars by the effect of thermonuclear reactions in the first phases of the formation of the stars. Many stars rise from the condensation of the gases and dust dispersed by the outbursts of supernovas. The stars thus originated are more feasible to have habitable planets than the stars with a lower metallicity because the stars with a low metallicity have a shorter life, related to their thermonuclear activity; thus, the stars with a low metallicity keep going active through so abbreviated time that they do not yield living beings to emerge and evolve on the planets orbiting them.
Most organic and inorganic compounds -especially water- are formed in the solar nebula thanks to fluctuations in the energy density, which causes phase transitions in the molecules that permit the spontaneous autosynthesis of simple organic and inorganic substances.
The water in the stellar nebulas permits the cooling of the interstellar medium, propitiating the synthesis of glycerol and more complex organic compounds, like ammonia, amino acids, lipids and perhaps globulins into holes and cracks of dust grains that contain water that suffers sudden phase transitions from solid phase to liquid phase and vice versa.
The ultraviolet radiation, the heat and other forms of stellar radiation, helped by condenser agents, cause the polymerization of simple compounds to make more organized molecules of hydrocarbons, carbohydrates, proteins and lipids, which are integrated like microscopic globules in the frozen water trapped by the granules of dust (fractals) of the planetary clouds.
When the planetary nebulas lower the temperature at a proper point, the spontaneous synthesis of microspheres with external membranes of lipoproteins occurs under the effect of UV radiation and the heat generated by the collisions among the particles of dust. The microspheres contain a larger diversity of organic compounds thanks to the agglomerative substrates that act like strata that facilitate the accumulation and interaction of substances; examples of agglomerative substrates are the granules of calcium phosphate, calcium carbonate, silicon carbide, graphite, fullerenes (allotropic forms of carbon) or Iron Sulfur -which can or cannot contain ice of water- and by the action of condenser agents (substances that promote the abiotic synthesis of simple and complex biomolecules; for example, HCN (Hydrogen Cyanide) and C2H2 (acetylene). These compounds are abundant in the interplanetary medium of early stars and it has been artificially confirmed that they act like condenser agents. The trials indicate that the biopolymerization of proteins and complex sugars is facilitated by these agents and by reactions promoted mainly by high energy bosons.
Going back to the microspheres, the particles of dust (fractals) suspended in the planetary atmospheres retain the microspheres into their holes and fissures. The dust grains work like protective shields of the biomolecules against the stars’ ionizing radiation, so the phase transitions permit the synthesis of more complex biomolecules, for example, waxes, phospholipids, proteins and lipoproteins. These molecules build highly stable and lasting membranes that contain a higher number of microspheres with diverse biological products; however, the single membranes are ephemeral because the radiation emitted by the stars that is received by the planets destroys them. However, many microspheres that are segregated from the surroundings by membranes or by membrane-like structures subsist in that hostile environment because they remain into dust grains containing icy water.
Due to their low resistance to the cosmic radiation, it is not feasible the synthesis of nucleotides in the interplanetary space. Probably, the nucleotides synthesize on the planets a long time after the emergence of the first living forms. Besides, the synthesis of molecules of nucleic acids does not occur spontaneously or no-spontaneously in nature. By this reason, the protobionts built in the planetary medium cannot have any form of nucleic acid (DNA or RNA).
The Gravitational Force of planets maintains to the small stellar dust grain accretions with microspheres wrapped by membrane amphiphilic in planetary orbits, forming dense clouds of dust, vapor of water, ammonia, acetylene, hydrogen cyanide, methane, carbon dioxide and other gases; however, the acceleration of the grains of dust and the intense heat emitted from the surface of the planets impede the setting down of the dust on the planetary surfaces. At later phases through the gestation of the planets, the water vapor condenses in the planetary atmospheres forming heavy drops that precipitate on the planetary soils dragging the grains of dust with and without microspheres with them.
Even suspended in the planetary atmospheres, the microspheres are agglutinated into the humid grains of dust to form prebiotic structures segregated by more complex amphiphilic membranes –known like protobionts- that are not yet living forms, but already experience transfers of energy as living forms (bionts) do.
When the planets chill fast and rains can occur, the fractals with and without protobionts are dragged down by the water drops unto the planets’ surfaces.
Once placed on the planetary grounds, resting on humid layers of soil or on the bottoms of shallow ponds, the protobionts can be maintained stable under dense clouds of dust and water vapor suspended in the planetary atmospheres which protect them from the intense cosmic radiation.
Thousands of millions of protobionts can be destroyed by the aggressive conditions of the planetary environments; nevertheless, when the planets make colder and the stars are less unstable, the basic structures of the protobionts can remain stable during more prolonged periods of time. The difference consists of being in microenvironments with the basic factors that permit them to resist and prevail under the pressure of the early planetary environments.
The later chemical evolution depends on the amalgamation of protobionts, one to other, by electrochemical affinity. The protobionts fuse one to other forming vesicles with continuous membranes. Those complex vesicles rest on the humid soils or in the bottom of shallow or subterranean ponds. The fractures and holes of soils, full of chemical substances, are covered by the biomembranes establishing microenvironments chemically similar to the cytosol of modern cells. It blocks the osmotic catastrophe that would occur if the hypothesis of the "nutritious broth" of Oparin were real. The paleontology and geological observations clearly indicate that the "nutritious broths" have not existed and cannot exist in nature.
Once fused, some protobionts become into bionts by possessing molecular configurations that are apt to experience the biotic phase thanks to successive chemical structural changes in the biomembranes. This intricate configuration of biomembranes permits the aggregate of polypeptides and glycopeptides that promotes changes in the magnetic fields which start patterns of electrochemical gradients that establishes an electrodynamic field that permits the transfer of energy through particles. The bionts (living beings) self-synthesize through this system. It is the mechanism by which any living form existing anywhere in the universe emerges.
From the viewpoint of my hypothesis, all the living beings existing on any planet can be generated from a single living and replicable biont. Its reproduction would be similar to yeast budding, but in total absence of nucleic acids. The autocatalytic proteins contain the necessary information for autocatalysis.
Let’s come back to the cosmic abiogenesis: The biomembranes extended on the bottoms of ponds, coating holes and cracks on soils packed with organic substances, carry out active transfers of fermions and compounds with the environment.
The incorporation of proteins, lipids, and other complex molecules to the cytosol promotes the formation of molecular structures specialized in the transfer of energy from the surroundings; for example, molecules of ATP Synthase, single RNA nucleotides, short molecules of RNA, NADP, ADP, etc. The small chains of RNA are synthesized by the autocatalytic proteins with biochemical affinity toward the nucleotides transferring the information of the amino acids sequences toward codifier molecules of RNA.
In this way, the bionts are maintained stable through longer periods, besides they can transfer the information of their individual characteristics through the sequences of RNA toward the new generated vesicles through the development of their cytosol. Protected under a darkened sky by suspended dust and diverse vapors, in deposits of water and at not more than 36° C, the bionts reproduce by means of the formation of vesicles that grow out from the membranes as bubbles or buds that have the same functional and structural characteristics of their ancestors.
The autocatalytic proteins, by their physicochemical characteristics, obligatorily direct the synthesis of simple molecules of RNA, forming longer chains each time containing all the information for the synthesis of the same autocatalytic proteins and identical RNA molecules. Later, the same autocatalytic proteins produce nucleotides of DNA and, after this, complete DNA chains.
The flexibility of this hypothesis permits us to assume that the Ribozymes are not necessary for the synthesis of biomolecules, which can be multiplied through the transformation of the quarter biomolecules of other proteins in the same one cytosol. For example, the reproduction of prions that are thought to possess molecular configurations very similar to the configuration of the primeval proteins.
Earth is not the unique planet of the solar system that had favorable conditions for the emergence of bionts. There are sidereal bodies where living beings could be formed like on Earth; however, although those extraterrestrial bionts had not the minimal possibilities of survival due to the inappropriate conditions of the planetary environments where they had been formed or due to sudden and extreme planetary climate transitions. For example, the living beings could emerge on Mars by the same epoch that on Earth, however, a sudden and severe climate change in the planet, occurred some 400 million years after its concretion, destroyed all the bionts that could be living on that planet. (Shuster and Weiss. Science. 2006).
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