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A species comes into existence and endures for a limited time and then it vanishes.
A visit to the nearest Natural History Museum should make it obvious to anyone that millions of species of plants and animals have existed on the Earth during the past three billion years. This is the estimated length of time that paleobiologists estimate that life has existed on our planet. The millions of existing museum fossils should also make it quite evident that the majority of these species no longer exist.
Understanding the origin and extinction of species is of paramount importance to our own existence and survival. Unfortunately, the vast majority of humans understand neither. About 90% of humankind professes to adhere to a religious philosophy that has absolutely no interest or concern in understanding the most fundamental ecological relationships that exist in nature. Human failure to respect this relationship has resulted in human failure in our own stewardship of our own planet.
For as long as fossils have been discovered by archaeologists and amateur naturalists, they have intrigued and amazed the human mind. Originally, fossils were simply considered amusing curiosities of nature or were explained by some religious tradition or mythology. But after years of serious examination and thoughtful reflection, it came to be acknowledged that these fossils were actually the historical remains and evidence of previous living species.
Not only do the various geological layers of the Earth´s surface have millions of very different fossils, but they seem to suggest a pattern of development. Successive geological layers present evidence of different species that were very similar but slightly different. The successive species give the obvious appearance of having slightly changed their fundamental characteristics
A small Eocene horse (54-34 million years ago) actually had four toes in the front and three toes in the back along with vestigial toes, Later, in the Miocene (24 mya) another horse, Miohippus had three toes. By the Pliocene (4 mya), there were several species of Equus that represented the beginning of modern horses. These horses were still pony size, but some of them had only one toe. The other toes were only vestigial remnants. By the late Pleistocene, the modern large one-toed horse had evolved. It can´t be proven that the later large horse was descended from the earlier smaller horse, but except for size they are very similar animals and descent with variation is the most probable natural explanation. (This oversimplified summary was not intended to include all of the several dozen species of horse ancestors that have been discovered. For a more complete history of horses go to www.talkorgins.org).
The idea that animals could change their characteristics (or evolve) in time, was considered over two thousand years ago by the ancient Greeks (Anaximander of Miletus). This idea was abandoned during the Middle Ages when religious theocracies dominated most European nations. These theocratic dogmas insisted that the Earth was only about six thousand years old. Biological evolution wasn´t reconsidered again until the 18th and 19th centuries.
The generally accepted estimate that the Earth was only a few thousand years old caused most 18th scientists, including biologists, to reject the concept of animals or plants slowly changing their characteristics (there simply wasn´t enough geological time). As geologists continued to find new ways to estimate the age of the Earth, it became more evident that the Earth was not just 6,000 years old but much closer to 6,000,000,000 years old. The fossils also indicated that for at least three billion years of that incomprehensible time span, there had been life on our planet. This new longer estimate of the Earth´s age was very compatible with the biological theory of slowly evolving life forms. The fossil evidence offered substantial proof that during the Earth´s long history, species of plants and animals had possessed different characteristics.
If we look at our own species, we recognize that human populations have many different characteristics (which are determined by genes). A few million years ago, the only humans on Earth lived in east Africa. They essentially had black skin, black hair and brown eyes. There were no white skinned, blond haired or blue eyed humans. And yet today these characteristics (genes) and many others obviously do exist. At some point during this time span, these new genes had to have come into existence.
This theory proposed two questions: (1) What was the origin of these variations and (2) how did a new species develop from an old species?
In addition to the geological discovery that the Earth was about six billion years old, geologists began to understand that the Earth was continually undergoing a very slow process of change. Erosion had taken about one million years to form the Grand Canyon in Arizona. These slow geological processes were gradually changing the entire surface of the planet. It is now generally accepted by geologists that the present land masses of the Earth´s surface were originally one single continent. All of the present continents and islands of the entire planet were together in an approximately circular continent called "Pangaea" (which means ´all earth´). One possible theory of the origin of Pangaea is that when the surface of the Earth was still molten liquid, the Moon had the same rotational period as the Earth (this is called orbital locking). This would have resulted in the Moon remaining in a fixed location over a single surface location (estimated to be the center of Pangaea in the present location of Egypt. If a person could have been in Egypt at that time, the moon would have remained directly overhead, permanently). The gravitational pull by the Moon on the liquid surface would have created a bulge exactly like the present tidal effect on the ocean (except that the present tidal effect has a drag, caused by the present location of the continents, which produces two bulges. If the Moon was in a fixed location, with a totally liquid Earth surface, this would only create one bulge. The same way, at the present time, that the same side of the Moon always faces the Earth, in orbital locking, the same side of the Earth would simultaneously face the Moon). As the Earth´s surface cooled, the bulge was about twice as thick as the rest of the crust. This bulge cooled to became the circular continent of Pangaea. This theory further proposes that as the Moon slowly began rotating around the Earth (moving to a larger orbit), the binary system (Earth and Moon) was no longer in balance (because the bulge was no longer located in line with the two centers of gravity). Pangaea became like a large lump in a spinning centrifuge. In order to rebalance the planet, the spinning planet, like a centrifuge, began breaking the bulge up into approximately four quadrants and spreading them out (the Asian quadrant remains unbroken because it´s east coast is in the direction of the Earth´s rotation). North and South America and the islands of the Indian Ocean and South China Sea are still moving away from the original center of Pangaea. (One quadrant broke approximately in the center, the western part becoming North America and the eastern part becoming northern Europe. The second quadrant broke in the center, the western half becoming South America and the eastern half becoming west Africa. The third quadrant was the most broken, forming the east coast of Africa, Australia, Indonesia, Antarctica, and all of the islands in the Indian Ocean and the South China Sea. The fourth quadrant, as mentioned above, remains unbroken. It is the large land mass of Asia, primarily China and the former USSR).
The break up of Pangaea is important in the evolution of life because it has been responsible for the creation of many different habitats and environments all over the Earth. The moving land masses have created mountains (along the western coasts of North and South America, which was the original west coast of Pangaea), valley, deserts, separate oceans, lakes, rivers, swamps and thousands of isolated islands. All of these very different environments are continually changing at different rates. These new environments continue to offer new opportunities for species diversification and evolution. The Galapagos Islands are a showplace for evolution (a group of islands in the Pacific Ocean) which inspired Darwin to question the old theories about the immutability of species.
Whenever one group of one species begins to exist in a different area or environment, it must adapt to the new environment in order to survive. New characteristics must be developed (evolved) which did not exist in the original group. When two groups that were originally one group develop enough unique characteristics that they can no longer interbreed, a new species has come into existence. (Sexual reproduction is a very complex chemical process in which a slight change in any stage of development can cause the whole process to fail).
Charles Darwin, during his world-wide voyage (1831-36), studied environments on almost all continents and hundreds of islands. He recognized this diversification as the origin of species and that the selection of characteristics was caused by the natural environment. Darwin methodologically studied this new theory for 23 years (1836-59) before publishing his basic ideas in "The Origin of Species by means of Natural Selection". In this volume, Darwin answered the question of ´how´ a new species is formed, but he couldn´t answer the question of where the new variation (genetic) came from. He acknowledged this failure in chapters five and six. This failure to explain the causes of mutation was due solely to the fact that the science of genetics had not yet been developed. This failure in no way invalidated his basic theory of Natural Selection which did not depend in any way on the causes of genetic variation, but only on their existence.
Every species of living organisms that have ever existed on our planet have had a different rate of evolution. Some species change very fast and some change very slow. The word evolution has one simple meaning. Evolution means change but almost nothing changes at the same rate. This confuses some people who wonder why some species appear to remain unchanged over long periods of time while other species change dramatically. When a species experiences very little observable change, it is primarily because it´s environment has also experienced very little change. A species that is well adapted to a basically stable environment doesn´t need any new characteristics to endure.
Change is always constant, but the rate of change is never constant. Environments are too complex. Every species lives in a different environment and every environment changes in a different way. A species environment or habitat includes everything that is related to their existence. It includes their food supply, predicators, prey, climate and everything else in their territory that is important for their survival. These are different for each species even if they live in the same geographic location. On a geological time scale, most environments change extremely slow, but they all change.
It is impossible to even estimate how many millions of species of plants and animals that have become extinct during the past three billion years. The hundreds of millions of fossils that fill our Natural History Museums are only the species that actually left a physical record. How many species didn´t leave any record of their existence? Almost all of the soft bodied species that existed for millions of years, before and after any shells or vertebrae evolved, have left little or no record of their existence. They have vanished without a trace. Most of them either became food for other species or their molecular structure simply dissolved into basic chemical elements.
In the science of the evolution of life, it is actually impossible to even define what is meant by the word ´species´. The word actually goes back to a time in the past, when biologists were unaware that species ever changed. When a species evolves gradually over a long period of time, there is no single moment when an old species ends and a new species begins. It is simply a continuous transition. In any one time period, the word species usually has a simple meaning related to reproduction. If two groups are able to interbreed, they are usually classified as belonging to the same species. If they can´t reproduce, they are classified as separate species. One current exception is the donkey and the horse. They are close enough related to produce an offspring, a mule, but the mule is sterile and can´t reproduce. These sterile offspring between two different closely related species are usually called hybrids in zoology or botany.
This definition of species, of course, only applies to species living in the same time period. It´s impossible to know if two species living thousands of years apart could reproduce. This can only be guessed at depending on whether or not they have similar characteristics.
In the mid 19th century, when Darwin wrote his books and monographs (mostly on biology and botany) the science of Genetics didn´t exist. The early pioneering work on plant breeding experiments by the Austrian monk Gregor Mendel had been published in an obscure publication in 1865 but most naturalists were unaware of it´s existence or it´s importance until it was rediscovered in 1900. Mendel´s studies created the modern science of Genetics.
Genetic variation and Natural Selection are now considered to be the major causes of evolution. Darwin recognized that the characteristics of a species that determine it´s survival were selected by the natural environment in which the species lived. But he could only guess at what biological mechanism could cause the variation of characteristics in the first place. How could the same group of Finches have so many different sizes of beaks? (see: The Beak of the Finch by Jonathan Weiner, 1994). How can an insect species become immune to a pesticide? Natural Selection explains why those insects who are accidentally born immune to a particular pesticide would survive, but it didn´t explain why a few had the immune characteristic in the first place. They had a characteristic which would serve no apparent purpose in the original environment. The selected few insects that had the immune characteristic would be the only survivors after the pesticide crop spraying and would produce the entire next generation. So the entire next generation would all have the same immune characteristic. This is of course, a big problem for farmers who must continually rotate pesticides used on crops. (Today organic farmers try to avoid using strong chemical pesticides, even though there is no legal definition of the word ´organic´). Each new generation of insects evolves an immunity to the pesticide used in the previous crop spraying.
This modern example of agricultural insects is a case of rapidly changing environments in which the species of insects have a very rapid rate of evolution. (The farmer is trying to make the insects extinct, while the insects are only trying to survive). This pesticide spraying of crops amounts to an overnight change in the environment for the insect species. This produces an overnight change in the gene pool of the insects. (A gene pool is the sum of all of the genes existing in the individuals of an interbreeding population). In the original generation of insects (before the pesticide spraying) a very small minority of insects had the immune genes. In the next generation (after the pesticide spraying) almost all insects had the immune genes. This amounts to a change in the frequency of these genes in the gene pool of the species from a small percentage to a large percentage.
This is the actual definition commonly used to define the word evolution. Whenever there is any change, an increase or a decrease in the frequency of any genes, in the gene pool of a species, the species is said to have evolved (because it has changed the frequency of a fundamental characteristic). From this definition, it is obvious that all species are always evolving, because the gene frequencies are always changing, even with a single birth or a single death. (The percentage of humans that have blue eyes, is not the same today as it was yesterday. The frequency has changed.)
Most environments, in contrast to this insect example, don´t change so rapidly. Environments change at different rates, some very slowly over thousands or millions of years. But compared to the estimated three billion years that life has been on our planet, a few thousand years can be a relatively short time period.
Biologists, paleobiologists and environmentalists have long recognized that many factors contribute to the extinction of a species. But these factors can almost all be grouped together under the broad category of the organism´s environment. Causes that are external to the living cells: diseases, excessive heat or cold, competition with other species, available food supply, sudden climate or environmental temperature changes, continental movements, meteorites and any chemical exposure (external or internal) are a few probable causes.
Most extinctions are caused by a change in the organism´s environment and the corresponding inability of the species to change fast enough to survive. (In the insect case, if none of the insects accidentally have the immune genes, they will all become extinct). All environments change at different rates and for different reasons. Any change, no matter how small, can have repercussions that effect other species. The balance of Nature can be very complex, interrelated and fragile. Any change that effects one species can effect dozens of other species.
"What a trifling difference must often determine which shall survive and which perish." Charles Darwin - letter to Asa Gray.
Because all environments change at different rates, all species must also change (evolve) at different rates. If an environment changes rapidly, then the species living in that environment must also change rapidly or face extinction. In a slow changing environment, a species must also change slowly if they are to survive. When a slow changing environment has remained relatively unchanged for a long period of time, many of the species in that environment have become very adapted to those conditions. These species don´t need to change and consequently have a very slow rate of evolution. Random genetic changes are eliminated because they are not needed or are harmful.
Simply stated, a species in a fast changing environment must have a more rapid capability for change and a species in a slow changing environment must have a slow rate of evolution in order to survive.
This difference in the rate of evolution has not been given enough attention or relative importance by biologists in explaining why some species vanish and others do not.
In reality, ironically, it is the species that is the most adapted to a slow changing environment and has developed a slow rate of evolution, that is in the greatest danger of becoming extinct. When the environment suddenly changes for any reason, natural or man-made, these species with a slow rate of evolution simply cannot change fast enough to survive. This is the simple explanation that is sufficient to explain almost all previous extinctions on the Earth.
Species with a rapid rate of evolution are better prepared to survive. Species with a slow rate of evolution are more likely to be in trouble. Nature doesn´t have a brain or the foresight to see the future. Nature doesn´t know that the environment will eventually change. Natural Selection is only trying to adapt to the present conditions.
The question might next be asked as to ´how´ a species develops a fast or a slow rate of evolution. At the cellular level or the genetic level, what actually causes a species to increase or decrease it´s genetic variation?
Most geneticists and biologists attribute genetic variation to a number of causes. Many of these can be classified as external to the living cell. Such as: light (solar radiation, cosmic rays or any light wavelength that can penetrate the nucleus of the cell, including nuclear radiation), heat (which can cause chemical changes in any part of the cell, including the DNA and the RNA), any chemicals (taken internally in food or drink or external by contact), diseases, parasites or any invading organisms can cause genetic damage. Some internal cellular changes have been identified such as accidental physical DNA recombination during cell division. Some of these are: chromosome inversion, duplication, crossing over, insertion and depletion. All of these are accidental changes or genetic mutations. It is unknown as to what percent each of these causes may contribute to the genetic variation of characteristics.
Many biologists believe that natural radiation is sufficient to explain all mutation phenomena. In the beginning of life on our planet, the Earth most likely had a very different atmosphere (possibly no ozone layer for protection from ultraviolet light) and consequently the Earth´s surface may have received much stronger radiation from the Sun, which could cause increased DNA mutation. If radiation was the primary cause of genetic change, this could account for the very slow rate of evolution during the early eras. The earliest life forms were extremely simple, such as a virus. Whether a virus is actually ´living´ actually depends on how the word ´living´ is defined. A virus is basically a chemical strand of DNA which cannot reproduce itself until it is in the presence of certain enzymes. (A virus can float around in the air without having any characteristics that could be called ´living´. However, when it enters a living animal´s system and is in the presence of enzymes, it begins dividing and growing). When are chemicals defined to be living? Is the physical chemical process of DNA duplication the definition of life? During the early eras of life on Earth, there was no sexual reproduction. When nature developed sexual reproduction, this undoubtedly speeded up the genetic diversity and rate of change.
Because Darwin had no knowledge of genetics, he was looking for a common cause for variation in both plants and animals. A large percentage of his studies were done on plants in his own garden in Down England.
Since plants and animals have completely different sources of energy, these sources should play a role in the genetic variation of each group. Plants basically have a more simplified organization. They are not physically active like animals and they remain basically stationary (generally moving only toward a light source), receiving their source of energy directly from the Sun and depending on the process of photosynthesis to produce carbohydrates. The Sun plays such a major role in their evolution, the solar radiation is probably sufficient to explain the genetic variation of plants.
However, animals are so fundamentally different than plants, that they should be considered separately. Unlike plants, animals produce their energy from the process of metabolism. This completely different energy source should play a significant part in the regular production of genetic variation. (This idea has never been acknowledged). The solar radiation may be sufficient to explain the variation in plants and the earliest single celled organisms, but the multi-celled and more biologically complex active animals need a more reliable source of genetic variation. There are many animals that live their entire lives in total darkness, underground, in caves, in the ocean depths or simply have nocturnal lifestyles. These animal species have almost no exposure to solar radiation, and yet they still evolve. However in all of these dark environments, they all still have the common characteristic of metabolism.
Some biologists conclude that these accidental random mutations (from all causes) are insufficient to explain the steady variation in characteristics needed to explain evolution in general, especially in animals. Natural Selection is adequate to explain the selection of the characteristics that already exist, but random external mutations (offered for plants and simple organisms) don´t seem to be able to adequately explain the origin of all of these genetic characteristics. (This continues to be controversial). During the three billion years of the evolution of life, it would seem more probable that nature could have developed a more reliable method of regularly producing genetic variations (for animals) than the occasional random external causes (primarily solar radiation) listed above.
The two features of the currently accepted mutation theory that seem to be incompatible are (1) all of these random mutation causes can be relatively the same for different species living in the same general environment while at the same time (2) every species has a different rate of evolution. If each species variation has the same external causes (whatever they may be), why don´t they all have the same rate of evolution? Why don´t all species simply evolve and adapt to any new environment regardless of whether it is changing at a fast rate or a slow rate? Why does any species ever become extinct? These are all good questions and must have a natural answer.
What seems to be missing from the above list of causes (especially for animals) is an internal built-in cellular cause for these variations (DNA mutations) which would relate to each individual species and to their relationship to their own environment. An internal chemical process within each cell would be more reliable than accidental external (solar radiation) causes. This would explain the different rates of change in a common environment.
Is there an internal cellular mechanism that would naturally explain the different rates of evolution in different animal species even if they are living in the same environment? An explanation that is directly caused by the relationship between the rate of environmental change and the rate of species change? Is there a natural internal process that is being overlooked?
All living things (except some very simple organisms such as viruses) consist of one or more cells. A cell consists of complex chemical substances know as protoplasm surrounded by a cell wall or membrane. Within the cell is the nucleus which is surrounded by another thinner membrane.
There is a very good reason that each cell has a nucleus. The function of the cell nucleus is to protect the vital information that is encoded in the DNA. Within the body of the cell there are many active chemicals. The body of the cell is the factory where protein production and all of the functions of the cell are performed. These active chemicals would rapidly damage the DNA if it were not protected by the nucleus membrane. The DNA is the blueprint for everything that the cell does or produces. (The DNA doesn´t actually go into the body of the cell, it sends copies of itself, called RNA, into the cell to do the work). (DNA is deoxyribonucleic acid that occurs in all but a very few simple organisms. This universally shared structure of all life on the Earth is the strongest evidence of the common relationship and common origin of all life on our planet. RNA is ribonucleic acid).
The following description is for the metabolism of animals. Plants should be considered separately. Photosynthesis is the somewhat analogous process in plants.
A very critical molecular component of these cellular chemicals of animals, are the ´free radicals´. These are carbon based molecules that have an unpaired electron (this is what makes them so reactive). These molecules are byproducts of the process of metabolism. These ´free radicals´ vary in amount depending on the activities of the organism. A very active species will have a more active metabolism and produce more ´free radical´ molecules. A less active species will have a slower metabolism and produce less ´free radical´ molecules. (Metabolism is from the Greek word ´metabole´ meaning ´change´. Metabolism is the life-sustaining chemical activity within the animal body. It is literally the ingestion and digestion of food to produce energy and nutrients).
What does this have to do with the rate of evolution of a species? The answer is - EVERYTHING. An active animal species has a large amount of ´free radicals´ and a less active species has a smaller amount of these active molecules.
There are two types of cell division. Mitosis (normal cells) and meiosis (sex cells). In mitosis the body cells divide to produce two (almost) identical cells (called haploids) each with a full set of 46 chromosomes (for humans). In meiosis the sex cells divide to produce male sperm or female eggs with only half of the chromosomes (23) (called diploid cells). A normal fertilized human ovum contains 46 chromosomes or 23 pairs, one chromosome of each pair is from the mother, the other from the father.
It is the changes introduced into the DNA during these two types of cell division that causes the different rates of evolution. The following offers a possible explanation of ´how´ this naturally occurs.
During the cell divisions of both types, the nucleus, which functions to protect the DNA is temporarily dissolved. Just prior to the cell dividing, the DNA is temporarily exposed to the active chemicals within the cell body. The DNA lumps together to try to protect itself but it is still exposed to danger. It is during this brief time that the DNA can acquire a change or mutation. The most active molecules in the cell body are the ´free radicals´. The unpaired electrons in these molecules readily attach themselves to almost anything that they come into contact with. If they come into contact with the DNA, they cause a random mutation. The amount of DNA mutation varies depending on how many ´free radicals´ are present. A species with a slow metabolism has few of these molecules and this causes a small amount of DNA mutations. A species with a very active metabolism has many of these molecules and this causes a large amount of DNA mutations. This is a critical difference. These ´free radicals´ cause random mutations at random locations in the DNA causing random variations in the characteristics of the species.
Because these random variations (mutations) are during two different types of cell divisions, they produce two different results.
In mitosis (normal cell division) a high amount of ´free radicals´ will increase the rate of change in normal body cells. This type of change is responsible for the process of ´aging´. This is literally a ´wearing out´ of the cell blueprint. Increasing the rate of change in the normal body cells, ´speeds up´ the aging process and results in a shorter lifespan for the individual. (This is why many people take antioxidants to eliminate these ´free radicals´ and slow down the aging process. Contrary to most common beliefs, aging is not related to time, it´s related to change which can be speeded up or slowed down).
In meiosis (sex cell division) a high amount of ´free radicals´ will increase the rate of change in the sex cells. This type of change has a completely different effect (than mitosis) because the sex cells pass the genetic information on to the next generation. A high amount of these molecules produces a greater amount of variation in the characteristics of the offspring of a species. This speeds up the rate of evolution.
These are the overall effects of an animal species being more or less active:
The increased metabolism produces more ´free radicals´ which in turn produces a shorter lifespan for the individuals of a species and more variation in the next generation. This speeds up the rate of evolution.
The decreased metabolism produces less ´free radicals´ which in turn produces a longer lifespan for the individuals of the species and less variation in the next generation. This slows down the rate of evolution.
The longer the time span between generations, the slower the process of evolution must proceed. Insects that have a short lifespan of only a few days, produce the next generation in this short time. This allows a rapid rate of evolution. A species that has 20 years between generations has a much slower rate of evolution.
Functioning together, these two characteristics control the rate of evolution of an animal species. When a species is facing a rapidly changing environment and there is great competition, the species must struggle harder to survive. This increases the metabolism and speeds up the rate of evolution. This is exactly what the species needs if it is to survive. In a changing environment, a species needs more variation in their characteristics in order to adapt. (This literally increases the raw material for Natural Selection. This gives Nature more choices. Simply speaking, those who work harder are more likely to survive and those who are lazy are more likely to fail).
When an animal species is existing in a slow changing environment and there is little competition, the species doesn´t have to struggle so hard to survive. If there is a lot of food available and life is easy, the species may literally become lazy. This slows down the metabolism and slows down the rate of evolution. This is exactly what the species needs. It´s already adapted to the environment and doesn´t need to evolve, so it doesn´t need to change any characteristics.
This metabolic process provides an explanation of a totally internal natural cellular mechanism that controls the rate of evolution of an animal species. It explains why different species have different rates of evolution in the same environment. The rate of evolution of each species is directly related to the relationship between its own characteristics and the rate of change of its environment. This explains why in a fast changing environment, those species with a slow rate of evolution don´t survive and those with a fast rate of evolution do survive.
(This present theory about the importance of ´free radicals´ and the metabolic process to genetic variation and evolution in animals, may or may not turn out to be significant. But it appears to offer some answers to some previous difficulties).
"There is nothing permanent except change." Heraclitus 544 bc
While the Earth and all of the environments on the Earth have always been in constant change, these changes have taken place at different rates. From a geological time perspective, most of these changes have been relatively slow and most of the species have been able to change fast enough to survive. It should be remembered that millions of species found only in fossils, did not become extinct, but evolved into a new species.
But often the environment changes came relatively rapidly, geologically speaking, and species with a slow rate of evolution could not survive and did become extinct. They left no descendants and completely vanished.
The delicate balance of nature between any animal species and the available food supply was generally responsible for limiting the population size of any species. This included our own species. As humans migrated and spread out over almost every continent, each group´s size (usually tribal, before the development of civilized states) was still limited by the available food supply. For hundreds of thousands of years humans were basically hunters, gatherers and fish-eaters. During this time, humans were like all other species and were as much a part of nature as any other living group. Humans were part of the natural ecological balance.
But humans did two things that ended this natural balance. The first and most important was the invention of agriculture. For the first time in the history of our planet, a species population size was not limited to the available food supply. Agriculture enabled humans to create an unlimited amount of food. This resulted in an unlimited runaway population growth (explosion). Human populations have been increasing exponentially ever since. It is totally unnatural and unsustainable to have unlimited population growth of any one species. (Sooner or later nature will put a stop to this exponential growth. Probably either by disease or starvation, which are already steadily increasing worldwide). This agricultural capability gives one species an unfair advantage over all other species on the planet. Since the Earth has limited areas that are habitable, the unlimited growth of one species must inevitable crowd out others. As human populations continue to grow exponentially over the surface of the Earth, an increasing number of habitats of other species will be threatened. No other species can compete under these conditions. Humans can live in almost any location on Earth, from the snowy regions of the far north to the hottest arid regions of the deserts. They can import food to any location.
These migrations and the escalating population growth of humans has introduced dozens of other threats to indigenous species world-wide. The escalating destruction of forests, the introduction of exotic (meaning alien or foreign) plants, animals and diseases into new environments can completely disrupt an ecological balance that Natural Selection has taken millions of years to create. Many alien plants and animals are introduced by humans into new habitats deliberately and many are introduced accidentally. Many are introduced without understanding the existing natural balance and the potential harm that they can cause.
The uncontrolled population size is also indirectly responsible for the over-exploitation of many species such as unrestricted whaling. This almost caused the extinction of the Grey Whale.
The invention of agriculture has resulted in the human population explosion which has directly assaulted many other habitats and species of both plants and animals.
The second disastrous human invention was the creation of scientific technology and manufacturing industries. While most people consider scientific technology to have been beneficial to civilization, it has been devastating to the natural environment. It has resulted in the construction of thousands of factories that irresponsibly dump tons of pollutants and toxic chemicals into all of our rivers, lakes and oceans. It has resulted in developing automobile engines that pour tons of pollution into our atmosphere. It has resulted in creating nuclear energy facilities and nuclear bombs that create nuclear waste that will continue to be radioactive for thousands of years. It has created synthetic products and plastic containers that are not biodegradable and will pollute our environment for countless centuries. Greenhouse gases from burning carbon based fuels are causing global warming which is on the verge of starting a runaway greenhouse effect for the entire planet.
The planet Venus is approximately the same size as the Earth and many studies indicate that in it´s early history it may have had an atmosphere similar to the present Earth. But the present high amount of CO2 in the Venus atmosphere has apparently created a runaway greenhouse effect. The present surface temperature is about 460 degrees C. At this boiling temperature all life is impossible. Venus has become a sweltering inferno.
Our modern technology is responsible for the current daily pumping of more and more CO2 into our own atmosphere. The temperature of the Earth is steadily increasing. Polar ice caps are melting, raising the level of the ocean and destroying virtually all habitats of Artic animals. Global Warming is not only altering the environments all over the planet, it´s threatening to terminate all life on the Earth. Many environmental scientists are warning that we are rapidly approaching the point of no return.
There are some astronomers who believe that throughout the billions of galaxies in the Universe, there are millions of intelligent civilizations similar to our own. They believe that these civilizations continue to grow until they invent scientific technology, and then they rapidly and thoughtlessly destroy themselves. If humans are a typical example, they´re probably right.
A visit to the nearest Natural History Museum should make it obvious to anyone that millions of species of plants and animals have existed on the Earth during the past three billion years. This is the estimated length of time that paleobiologists estimate that life has existed on our planet. The millions of existing museum fossils should also make it quite evident that the majority of these species no longer exist.
Understanding the origin and extinction of species is of paramount importance to our own existence and survival. Unfortunately, the vast majority of humans understand neither. About 90% of humankind professes to adhere to a religious philosophy that has absolutely no interest or concern in understanding the most fundamental ecological relationships that exist in nature. Human failure to respect this relationship has resulted in human failure in our own stewardship of our own planet.
For as long as fossils have been discovered by archaeologists and amateur naturalists, they have intrigued and amazed the human mind. Originally, fossils were simply considered amusing curiosities of nature or were explained by some religious tradition or mythology. But after years of serious examination and thoughtful reflection, it came to be acknowledged that these fossils were actually the historical remains and evidence of previous living species.
Not only do the various geological layers of the Earth´s surface have millions of very different fossils, but they seem to suggest a pattern of development. Successive geological layers present evidence of different species that were very similar but slightly different. The successive species give the obvious appearance of having slightly changed their fundamental characteristics
A small Eocene horse (54-34 million years ago) actually had four toes in the front and three toes in the back along with vestigial toes, Later, in the Miocene (24 mya) another horse, Miohippus had three toes. By the Pliocene (4 mya), there were several species of Equus that represented the beginning of modern horses. These horses were still pony size, but some of them had only one toe. The other toes were only vestigial remnants. By the late Pleistocene, the modern large one-toed horse had evolved. It can´t be proven that the later large horse was descended from the earlier smaller horse, but except for size they are very similar animals and descent with variation is the most probable natural explanation. (This oversimplified summary was not intended to include all of the several dozen species of horse ancestors that have been discovered. For a more complete history of horses go to www.talkorgins.org).
The idea that animals could change their characteristics (or evolve) in time, was considered over two thousand years ago by the ancient Greeks (Anaximander of Miletus). This idea was abandoned during the Middle Ages when religious theocracies dominated most European nations. These theocratic dogmas insisted that the Earth was only about six thousand years old. Biological evolution wasn´t reconsidered again until the 18th and 19th centuries.
The generally accepted estimate that the Earth was only a few thousand years old caused most 18th scientists, including biologists, to reject the concept of animals or plants slowly changing their characteristics (there simply wasn´t enough geological time). As geologists continued to find new ways to estimate the age of the Earth, it became more evident that the Earth was not just 6,000 years old but much closer to 6,000,000,000 years old. The fossils also indicated that for at least three billion years of that incomprehensible time span, there had been life on our planet. This new longer estimate of the Earth´s age was very compatible with the biological theory of slowly evolving life forms. The fossil evidence offered substantial proof that during the Earth´s long history, species of plants and animals had possessed different characteristics.
If we look at our own species, we recognize that human populations have many different characteristics (which are determined by genes). A few million years ago, the only humans on Earth lived in east Africa. They essentially had black skin, black hair and brown eyes. There were no white skinned, blond haired or blue eyed humans. And yet today these characteristics (genes) and many others obviously do exist. At some point during this time span, these new genes had to have come into existence.
This theory proposed two questions: (1) What was the origin of these variations and (2) how did a new species develop from an old species?
In addition to the geological discovery that the Earth was about six billion years old, geologists began to understand that the Earth was continually undergoing a very slow process of change. Erosion had taken about one million years to form the Grand Canyon in Arizona. These slow geological processes were gradually changing the entire surface of the planet. It is now generally accepted by geologists that the present land masses of the Earth´s surface were originally one single continent. All of the present continents and islands of the entire planet were together in an approximately circular continent called "Pangaea" (which means ´all earth´). One possible theory of the origin of Pangaea is that when the surface of the Earth was still molten liquid, the Moon had the same rotational period as the Earth (this is called orbital locking). This would have resulted in the Moon remaining in a fixed location over a single surface location (estimated to be the center of Pangaea in the present location of Egypt. If a person could have been in Egypt at that time, the moon would have remained directly overhead, permanently). The gravitational pull by the Moon on the liquid surface would have created a bulge exactly like the present tidal effect on the ocean (except that the present tidal effect has a drag, caused by the present location of the continents, which produces two bulges. If the Moon was in a fixed location, with a totally liquid Earth surface, this would only create one bulge. The same way, at the present time, that the same side of the Moon always faces the Earth, in orbital locking, the same side of the Earth would simultaneously face the Moon). As the Earth´s surface cooled, the bulge was about twice as thick as the rest of the crust. This bulge cooled to became the circular continent of Pangaea. This theory further proposes that as the Moon slowly began rotating around the Earth (moving to a larger orbit), the binary system (Earth and Moon) was no longer in balance (because the bulge was no longer located in line with the two centers of gravity). Pangaea became like a large lump in a spinning centrifuge. In order to rebalance the planet, the spinning planet, like a centrifuge, began breaking the bulge up into approximately four quadrants and spreading them out (the Asian quadrant remains unbroken because it´s east coast is in the direction of the Earth´s rotation). North and South America and the islands of the Indian Ocean and South China Sea are still moving away from the original center of Pangaea. (One quadrant broke approximately in the center, the western part becoming North America and the eastern part becoming northern Europe. The second quadrant broke in the center, the western half becoming South America and the eastern half becoming west Africa. The third quadrant was the most broken, forming the east coast of Africa, Australia, Indonesia, Antarctica, and all of the islands in the Indian Ocean and the South China Sea. The fourth quadrant, as mentioned above, remains unbroken. It is the large land mass of Asia, primarily China and the former USSR).
The break up of Pangaea is important in the evolution of life because it has been responsible for the creation of many different habitats and environments all over the Earth. The moving land masses have created mountains (along the western coasts of North and South America, which was the original west coast of Pangaea), valley, deserts, separate oceans, lakes, rivers, swamps and thousands of isolated islands. All of these very different environments are continually changing at different rates. These new environments continue to offer new opportunities for species diversification and evolution. The Galapagos Islands are a showplace for evolution (a group of islands in the Pacific Ocean) which inspired Darwin to question the old theories about the immutability of species.
Whenever one group of one species begins to exist in a different area or environment, it must adapt to the new environment in order to survive. New characteristics must be developed (evolved) which did not exist in the original group. When two groups that were originally one group develop enough unique characteristics that they can no longer interbreed, a new species has come into existence. (Sexual reproduction is a very complex chemical process in which a slight change in any stage of development can cause the whole process to fail).
Charles Darwin, during his world-wide voyage (1831-36), studied environments on almost all continents and hundreds of islands. He recognized this diversification as the origin of species and that the selection of characteristics was caused by the natural environment. Darwin methodologically studied this new theory for 23 years (1836-59) before publishing his basic ideas in "The Origin of Species by means of Natural Selection". In this volume, Darwin answered the question of ´how´ a new species is formed, but he couldn´t answer the question of where the new variation (genetic) came from. He acknowledged this failure in chapters five and six. This failure to explain the causes of mutation was due solely to the fact that the science of genetics had not yet been developed. This failure in no way invalidated his basic theory of Natural Selection which did not depend in any way on the causes of genetic variation, but only on their existence.
Every species of living organisms that have ever existed on our planet have had a different rate of evolution. Some species change very fast and some change very slow. The word evolution has one simple meaning. Evolution means change but almost nothing changes at the same rate. This confuses some people who wonder why some species appear to remain unchanged over long periods of time while other species change dramatically. When a species experiences very little observable change, it is primarily because it´s environment has also experienced very little change. A species that is well adapted to a basically stable environment doesn´t need any new characteristics to endure.
Change is always constant, but the rate of change is never constant. Environments are too complex. Every species lives in a different environment and every environment changes in a different way. A species environment or habitat includes everything that is related to their existence. It includes their food supply, predicators, prey, climate and everything else in their territory that is important for their survival. These are different for each species even if they live in the same geographic location. On a geological time scale, most environments change extremely slow, but they all change.
It is impossible to even estimate how many millions of species of plants and animals that have become extinct during the past three billion years. The hundreds of millions of fossils that fill our Natural History Museums are only the species that actually left a physical record. How many species didn´t leave any record of their existence? Almost all of the soft bodied species that existed for millions of years, before and after any shells or vertebrae evolved, have left little or no record of their existence. They have vanished without a trace. Most of them either became food for other species or their molecular structure simply dissolved into basic chemical elements.
In the science of the evolution of life, it is actually impossible to even define what is meant by the word ´species´. The word actually goes back to a time in the past, when biologists were unaware that species ever changed. When a species evolves gradually over a long period of time, there is no single moment when an old species ends and a new species begins. It is simply a continuous transition. In any one time period, the word species usually has a simple meaning related to reproduction. If two groups are able to interbreed, they are usually classified as belonging to the same species. If they can´t reproduce, they are classified as separate species. One current exception is the donkey and the horse. They are close enough related to produce an offspring, a mule, but the mule is sterile and can´t reproduce. These sterile offspring between two different closely related species are usually called hybrids in zoology or botany.
This definition of species, of course, only applies to species living in the same time period. It´s impossible to know if two species living thousands of years apart could reproduce. This can only be guessed at depending on whether or not they have similar characteristics.
In the mid 19th century, when Darwin wrote his books and monographs (mostly on biology and botany) the science of Genetics didn´t exist. The early pioneering work on plant breeding experiments by the Austrian monk Gregor Mendel had been published in an obscure publication in 1865 but most naturalists were unaware of it´s existence or it´s importance until it was rediscovered in 1900. Mendel´s studies created the modern science of Genetics.
Genetic variation and Natural Selection are now considered to be the major causes of evolution. Darwin recognized that the characteristics of a species that determine it´s survival were selected by the natural environment in which the species lived. But he could only guess at what biological mechanism could cause the variation of characteristics in the first place. How could the same group of Finches have so many different sizes of beaks? (see: The Beak of the Finch by Jonathan Weiner, 1994). How can an insect species become immune to a pesticide? Natural Selection explains why those insects who are accidentally born immune to a particular pesticide would survive, but it didn´t explain why a few had the immune characteristic in the first place. They had a characteristic which would serve no apparent purpose in the original environment. The selected few insects that had the immune characteristic would be the only survivors after the pesticide crop spraying and would produce the entire next generation. So the entire next generation would all have the same immune characteristic. This is of course, a big problem for farmers who must continually rotate pesticides used on crops. (Today organic farmers try to avoid using strong chemical pesticides, even though there is no legal definition of the word ´organic´). Each new generation of insects evolves an immunity to the pesticide used in the previous crop spraying.
This modern example of agricultural insects is a case of rapidly changing environments in which the species of insects have a very rapid rate of evolution. (The farmer is trying to make the insects extinct, while the insects are only trying to survive). This pesticide spraying of crops amounts to an overnight change in the environment for the insect species. This produces an overnight change in the gene pool of the insects. (A gene pool is the sum of all of the genes existing in the individuals of an interbreeding population). In the original generation of insects (before the pesticide spraying) a very small minority of insects had the immune genes. In the next generation (after the pesticide spraying) almost all insects had the immune genes. This amounts to a change in the frequency of these genes in the gene pool of the species from a small percentage to a large percentage.
This is the actual definition commonly used to define the word evolution. Whenever there is any change, an increase or a decrease in the frequency of any genes, in the gene pool of a species, the species is said to have evolved (because it has changed the frequency of a fundamental characteristic). From this definition, it is obvious that all species are always evolving, because the gene frequencies are always changing, even with a single birth or a single death. (The percentage of humans that have blue eyes, is not the same today as it was yesterday. The frequency has changed.)
Most environments, in contrast to this insect example, don´t change so rapidly. Environments change at different rates, some very slowly over thousands or millions of years. But compared to the estimated three billion years that life has been on our planet, a few thousand years can be a relatively short time period.
Biologists, paleobiologists and environmentalists have long recognized that many factors contribute to the extinction of a species. But these factors can almost all be grouped together under the broad category of the organism´s environment. Causes that are external to the living cells: diseases, excessive heat or cold, competition with other species, available food supply, sudden climate or environmental temperature changes, continental movements, meteorites and any chemical exposure (external or internal) are a few probable causes.
Most extinctions are caused by a change in the organism´s environment and the corresponding inability of the species to change fast enough to survive. (In the insect case, if none of the insects accidentally have the immune genes, they will all become extinct). All environments change at different rates and for different reasons. Any change, no matter how small, can have repercussions that effect other species. The balance of Nature can be very complex, interrelated and fragile. Any change that effects one species can effect dozens of other species.
"What a trifling difference must often determine which shall survive and which perish." Charles Darwin - letter to Asa Gray.
Because all environments change at different rates, all species must also change (evolve) at different rates. If an environment changes rapidly, then the species living in that environment must also change rapidly or face extinction. In a slow changing environment, a species must also change slowly if they are to survive. When a slow changing environment has remained relatively unchanged for a long period of time, many of the species in that environment have become very adapted to those conditions. These species don´t need to change and consequently have a very slow rate of evolution. Random genetic changes are eliminated because they are not needed or are harmful.
Simply stated, a species in a fast changing environment must have a more rapid capability for change and a species in a slow changing environment must have a slow rate of evolution in order to survive.
This difference in the rate of evolution has not been given enough attention or relative importance by biologists in explaining why some species vanish and others do not.
In reality, ironically, it is the species that is the most adapted to a slow changing environment and has developed a slow rate of evolution, that is in the greatest danger of becoming extinct. When the environment suddenly changes for any reason, natural or man-made, these species with a slow rate of evolution simply cannot change fast enough to survive. This is the simple explanation that is sufficient to explain almost all previous extinctions on the Earth.
Species with a rapid rate of evolution are better prepared to survive. Species with a slow rate of evolution are more likely to be in trouble. Nature doesn´t have a brain or the foresight to see the future. Nature doesn´t know that the environment will eventually change. Natural Selection is only trying to adapt to the present conditions.
The question might next be asked as to ´how´ a species develops a fast or a slow rate of evolution. At the cellular level or the genetic level, what actually causes a species to increase or decrease it´s genetic variation?
Most geneticists and biologists attribute genetic variation to a number of causes. Many of these can be classified as external to the living cell. Such as: light (solar radiation, cosmic rays or any light wavelength that can penetrate the nucleus of the cell, including nuclear radiation), heat (which can cause chemical changes in any part of the cell, including the DNA and the RNA), any chemicals (taken internally in food or drink or external by contact), diseases, parasites or any invading organisms can cause genetic damage. Some internal cellular changes have been identified such as accidental physical DNA recombination during cell division. Some of these are: chromosome inversion, duplication, crossing over, insertion and depletion. All of these are accidental changes or genetic mutations. It is unknown as to what percent each of these causes may contribute to the genetic variation of characteristics.
Many biologists believe that natural radiation is sufficient to explain all mutation phenomena. In the beginning of life on our planet, the Earth most likely had a very different atmosphere (possibly no ozone layer for protection from ultraviolet light) and consequently the Earth´s surface may have received much stronger radiation from the Sun, which could cause increased DNA mutation. If radiation was the primary cause of genetic change, this could account for the very slow rate of evolution during the early eras. The earliest life forms were extremely simple, such as a virus. Whether a virus is actually ´living´ actually depends on how the word ´living´ is defined. A virus is basically a chemical strand of DNA which cannot reproduce itself until it is in the presence of certain enzymes. (A virus can float around in the air without having any characteristics that could be called ´living´. However, when it enters a living animal´s system and is in the presence of enzymes, it begins dividing and growing). When are chemicals defined to be living? Is the physical chemical process of DNA duplication the definition of life? During the early eras of life on Earth, there was no sexual reproduction. When nature developed sexual reproduction, this undoubtedly speeded up the genetic diversity and rate of change.
Because Darwin had no knowledge of genetics, he was looking for a common cause for variation in both plants and animals. A large percentage of his studies were done on plants in his own garden in Down England.
Since plants and animals have completely different sources of energy, these sources should play a role in the genetic variation of each group. Plants basically have a more simplified organization. They are not physically active like animals and they remain basically stationary (generally moving only toward a light source), receiving their source of energy directly from the Sun and depending on the process of photosynthesis to produce carbohydrates. The Sun plays such a major role in their evolution, the solar radiation is probably sufficient to explain the genetic variation of plants.
However, animals are so fundamentally different than plants, that they should be considered separately. Unlike plants, animals produce their energy from the process of metabolism. This completely different energy source should play a significant part in the regular production of genetic variation. (This idea has never been acknowledged). The solar radiation may be sufficient to explain the variation in plants and the earliest single celled organisms, but the multi-celled and more biologically complex active animals need a more reliable source of genetic variation. There are many animals that live their entire lives in total darkness, underground, in caves, in the ocean depths or simply have nocturnal lifestyles. These animal species have almost no exposure to solar radiation, and yet they still evolve. However in all of these dark environments, they all still have the common characteristic of metabolism.
Some biologists conclude that these accidental random mutations (from all causes) are insufficient to explain the steady variation in characteristics needed to explain evolution in general, especially in animals. Natural Selection is adequate to explain the selection of the characteristics that already exist, but random external mutations (offered for plants and simple organisms) don´t seem to be able to adequately explain the origin of all of these genetic characteristics. (This continues to be controversial). During the three billion years of the evolution of life, it would seem more probable that nature could have developed a more reliable method of regularly producing genetic variations (for animals) than the occasional random external causes (primarily solar radiation) listed above.
The two features of the currently accepted mutation theory that seem to be incompatible are (1) all of these random mutation causes can be relatively the same for different species living in the same general environment while at the same time (2) every species has a different rate of evolution. If each species variation has the same external causes (whatever they may be), why don´t they all have the same rate of evolution? Why don´t all species simply evolve and adapt to any new environment regardless of whether it is changing at a fast rate or a slow rate? Why does any species ever become extinct? These are all good questions and must have a natural answer.
What seems to be missing from the above list of causes (especially for animals) is an internal built-in cellular cause for these variations (DNA mutations) which would relate to each individual species and to their relationship to their own environment. An internal chemical process within each cell would be more reliable than accidental external (solar radiation) causes. This would explain the different rates of change in a common environment.
Is there an internal cellular mechanism that would naturally explain the different rates of evolution in different animal species even if they are living in the same environment? An explanation that is directly caused by the relationship between the rate of environmental change and the rate of species change? Is there a natural internal process that is being overlooked?
All living things (except some very simple organisms such as viruses) consist of one or more cells. A cell consists of complex chemical substances know as protoplasm surrounded by a cell wall or membrane. Within the cell is the nucleus which is surrounded by another thinner membrane.
There is a very good reason that each cell has a nucleus. The function of the cell nucleus is to protect the vital information that is encoded in the DNA. Within the body of the cell there are many active chemicals. The body of the cell is the factory where protein production and all of the functions of the cell are performed. These active chemicals would rapidly damage the DNA if it were not protected by the nucleus membrane. The DNA is the blueprint for everything that the cell does or produces. (The DNA doesn´t actually go into the body of the cell, it sends copies of itself, called RNA, into the cell to do the work). (DNA is deoxyribonucleic acid that occurs in all but a very few simple organisms. This universally shared structure of all life on the Earth is the strongest evidence of the common relationship and common origin of all life on our planet. RNA is ribonucleic acid).
The following description is for the metabolism of animals. Plants should be considered separately. Photosynthesis is the somewhat analogous process in plants.
A very critical molecular component of these cellular chemicals of animals, are the ´free radicals´. These are carbon based molecules that have an unpaired electron (this is what makes them so reactive). These molecules are byproducts of the process of metabolism. These ´free radicals´ vary in amount depending on the activities of the organism. A very active species will have a more active metabolism and produce more ´free radical´ molecules. A less active species will have a slower metabolism and produce less ´free radical´ molecules. (Metabolism is from the Greek word ´metabole´ meaning ´change´. Metabolism is the life-sustaining chemical activity within the animal body. It is literally the ingestion and digestion of food to produce energy and nutrients).
What does this have to do with the rate of evolution of a species? The answer is - EVERYTHING. An active animal species has a large amount of ´free radicals´ and a less active species has a smaller amount of these active molecules.
There are two types of cell division. Mitosis (normal cells) and meiosis (sex cells). In mitosis the body cells divide to produce two (almost) identical cells (called haploids) each with a full set of 46 chromosomes (for humans). In meiosis the sex cells divide to produce male sperm or female eggs with only half of the chromosomes (23) (called diploid cells). A normal fertilized human ovum contains 46 chromosomes or 23 pairs, one chromosome of each pair is from the mother, the other from the father.
It is the changes introduced into the DNA during these two types of cell division that causes the different rates of evolution. The following offers a possible explanation of ´how´ this naturally occurs.
During the cell divisions of both types, the nucleus, which functions to protect the DNA is temporarily dissolved. Just prior to the cell dividing, the DNA is temporarily exposed to the active chemicals within the cell body. The DNA lumps together to try to protect itself but it is still exposed to danger. It is during this brief time that the DNA can acquire a change or mutation. The most active molecules in the cell body are the ´free radicals´. The unpaired electrons in these molecules readily attach themselves to almost anything that they come into contact with. If they come into contact with the DNA, they cause a random mutation. The amount of DNA mutation varies depending on how many ´free radicals´ are present. A species with a slow metabolism has few of these molecules and this causes a small amount of DNA mutations. A species with a very active metabolism has many of these molecules and this causes a large amount of DNA mutations. This is a critical difference. These ´free radicals´ cause random mutations at random locations in the DNA causing random variations in the characteristics of the species.
Because these random variations (mutations) are during two different types of cell divisions, they produce two different results.
In mitosis (normal cell division) a high amount of ´free radicals´ will increase the rate of change in normal body cells. This type of change is responsible for the process of ´aging´. This is literally a ´wearing out´ of the cell blueprint. Increasing the rate of change in the normal body cells, ´speeds up´ the aging process and results in a shorter lifespan for the individual. (This is why many people take antioxidants to eliminate these ´free radicals´ and slow down the aging process. Contrary to most common beliefs, aging is not related to time, it´s related to change which can be speeded up or slowed down).
In meiosis (sex cell division) a high amount of ´free radicals´ will increase the rate of change in the sex cells. This type of change has a completely different effect (than mitosis) because the sex cells pass the genetic information on to the next generation. A high amount of these molecules produces a greater amount of variation in the characteristics of the offspring of a species. This speeds up the rate of evolution.
These are the overall effects of an animal species being more or less active:
The increased metabolism produces more ´free radicals´ which in turn produces a shorter lifespan for the individuals of a species and more variation in the next generation. This speeds up the rate of evolution.
The decreased metabolism produces less ´free radicals´ which in turn produces a longer lifespan for the individuals of the species and less variation in the next generation. This slows down the rate of evolution.
The longer the time span between generations, the slower the process of evolution must proceed. Insects that have a short lifespan of only a few days, produce the next generation in this short time. This allows a rapid rate of evolution. A species that has 20 years between generations has a much slower rate of evolution.
Functioning together, these two characteristics control the rate of evolution of an animal species. When a species is facing a rapidly changing environment and there is great competition, the species must struggle harder to survive. This increases the metabolism and speeds up the rate of evolution. This is exactly what the species needs if it is to survive. In a changing environment, a species needs more variation in their characteristics in order to adapt. (This literally increases the raw material for Natural Selection. This gives Nature more choices. Simply speaking, those who work harder are more likely to survive and those who are lazy are more likely to fail).
When an animal species is existing in a slow changing environment and there is little competition, the species doesn´t have to struggle so hard to survive. If there is a lot of food available and life is easy, the species may literally become lazy. This slows down the metabolism and slows down the rate of evolution. This is exactly what the species needs. It´s already adapted to the environment and doesn´t need to evolve, so it doesn´t need to change any characteristics.
This metabolic process provides an explanation of a totally internal natural cellular mechanism that controls the rate of evolution of an animal species. It explains why different species have different rates of evolution in the same environment. The rate of evolution of each species is directly related to the relationship between its own characteristics and the rate of change of its environment. This explains why in a fast changing environment, those species with a slow rate of evolution don´t survive and those with a fast rate of evolution do survive.
(This present theory about the importance of ´free radicals´ and the metabolic process to genetic variation and evolution in animals, may or may not turn out to be significant. But it appears to offer some answers to some previous difficulties).
"There is nothing permanent except change." Heraclitus 544 bc
While the Earth and all of the environments on the Earth have always been in constant change, these changes have taken place at different rates. From a geological time perspective, most of these changes have been relatively slow and most of the species have been able to change fast enough to survive. It should be remembered that millions of species found only in fossils, did not become extinct, but evolved into a new species.
But often the environment changes came relatively rapidly, geologically speaking, and species with a slow rate of evolution could not survive and did become extinct. They left no descendants and completely vanished.
The delicate balance of nature between any animal species and the available food supply was generally responsible for limiting the population size of any species. This included our own species. As humans migrated and spread out over almost every continent, each group´s size (usually tribal, before the development of civilized states) was still limited by the available food supply. For hundreds of thousands of years humans were basically hunters, gatherers and fish-eaters. During this time, humans were like all other species and were as much a part of nature as any other living group. Humans were part of the natural ecological balance.
But humans did two things that ended this natural balance. The first and most important was the invention of agriculture. For the first time in the history of our planet, a species population size was not limited to the available food supply. Agriculture enabled humans to create an unlimited amount of food. This resulted in an unlimited runaway population growth (explosion). Human populations have been increasing exponentially ever since. It is totally unnatural and unsustainable to have unlimited population growth of any one species. (Sooner or later nature will put a stop to this exponential growth. Probably either by disease or starvation, which are already steadily increasing worldwide). This agricultural capability gives one species an unfair advantage over all other species on the planet. Since the Earth has limited areas that are habitable, the unlimited growth of one species must inevitable crowd out others. As human populations continue to grow exponentially over the surface of the Earth, an increasing number of habitats of other species will be threatened. No other species can compete under these conditions. Humans can live in almost any location on Earth, from the snowy regions of the far north to the hottest arid regions of the deserts. They can import food to any location.
These migrations and the escalating population growth of humans has introduced dozens of other threats to indigenous species world-wide. The escalating destruction of forests, the introduction of exotic (meaning alien or foreign) plants, animals and diseases into new environments can completely disrupt an ecological balance that Natural Selection has taken millions of years to create. Many alien plants and animals are introduced by humans into new habitats deliberately and many are introduced accidentally. Many are introduced without understanding the existing natural balance and the potential harm that they can cause.
The uncontrolled population size is also indirectly responsible for the over-exploitation of many species such as unrestricted whaling. This almost caused the extinction of the Grey Whale.
The invention of agriculture has resulted in the human population explosion which has directly assaulted many other habitats and species of both plants and animals.
The second disastrous human invention was the creation of scientific technology and manufacturing industries. While most people consider scientific technology to have been beneficial to civilization, it has been devastating to the natural environment. It has resulted in the construction of thousands of factories that irresponsibly dump tons of pollutants and toxic chemicals into all of our rivers, lakes and oceans. It has resulted in developing automobile engines that pour tons of pollution into our atmosphere. It has resulted in creating nuclear energy facilities and nuclear bombs that create nuclear waste that will continue to be radioactive for thousands of years. It has created synthetic products and plastic containers that are not biodegradable and will pollute our environment for countless centuries. Greenhouse gases from burning carbon based fuels are causing global warming which is on the verge of starting a runaway greenhouse effect for the entire planet.
The planet Venus is approximately the same size as the Earth and many studies indicate that in it´s early history it may have had an atmosphere similar to the present Earth. But the present high amount of CO2 in the Venus atmosphere has apparently created a runaway greenhouse effect. The present surface temperature is about 460 degrees C. At this boiling temperature all life is impossible. Venus has become a sweltering inferno.
Our modern technology is responsible for the current daily pumping of more and more CO2 into our own atmosphere. The temperature of the Earth is steadily increasing. Polar ice caps are melting, raising the level of the ocean and destroying virtually all habitats of Artic animals. Global Warming is not only altering the environments all over the planet, it´s threatening to terminate all life on the Earth. Many environmental scientists are warning that we are rapidly approaching the point of no return.
There are some astronomers who believe that throughout the billions of galaxies in the Universe, there are millions of intelligent civilizations similar to our own. They believe that these civilizations continue to grow until they invent scientific technology, and then they rapidly and thoughtlessly destroy themselves. If humans are a typical example, they´re probably right.
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