One: Inheritance, Mutation, and Evolution

Men produce sperm and women produce eggs. Both are cells. When a sperm cell combines with an egg cell it forms a fertilized egg. Fertilized eggs can split into two exact same cells, which can then split into four, then eight such cells, eventually forming a living person.

The formation of life is the result of cell division. This applies to humans and all other organisms. Why are people different from each other, and why are animals and plants each different in their own way? The secret lies within the biological cells.

There is a substance called DNA in cells; its basic unit is deoxynucleotides, and it stores the genetic code of life. Simply speaking, a cell is made of the central nucleus and the peripheral cytoplasm. There is a very important material called chromosomes inside the nucleus; it is the carrier of DNA, and it always exists in pairs: one half comes from the male parent, and the other from the female parent. This means that half of our traits are decided by the male parent, and the other half by the female parent. Humans have twenty three pairs of chromosomes.

DNA molecules are composed of two long chains in a double helix structure, which resembles a spiral ladder twisted together. The handrails of the ladder are made of phosphoric acid and deoxyribose, which is the backbone of DNA. The steps of the ladder are made of base pairs, and the genetic codes of life are engraved on them. The “genes” we usually refer to as the deciding factors of traits are fragments of DNA. According to results from the Human Genome Project, it is estimated that humans have twenty thousand to twenty-five thousand genes.

The two chains that form the DNA double helix structure are identical to each other but reverse in direction—that is, the two ends of the chain are reversed and wound together in a right-hand spiral. During cell division, the two long chains of the DNA molecules are split to form two separate strands, each of which is paired with other deoxynucleotides to form a new double helix structure. Each newly formed spiral is exactly the same as the original spiral, producing two identical DNA molecules. This is the self-replication function of DNA.

When we say that the DNA molecule self-replicates to form two double spirals exactly the same, we refer to an almost 100 percent accuracy. However, nothing is foolproof, and one accidental error will appear among numerous perfect copies. This is called a “mutation.”

On ranches, we sometimes find that cattle or sheep will produce an off spring completely different from its parents; this is an example of mutation. Distinctly different crop seedlings will also appear on farms, which is also mutation. The same phenomenon happens in humans as well. All creatures mutate; some mutations are inherited and some are not. Mutations are usually not beneficial, as they produce weaker individuals. Cancer is one such adverse mutation within the body; radiation syndrome is another example where high-energy rays penetrate into the cell’s nucleus and destroys the DNA structure, causing mutation.

In biological mutation, sometimes there will occur a mutation that produces a stronger individual. If this mutation can be inherited, it will form a stronger species. This is what we call evolution. Earth’s primitive life developed into the vibrant variety of creatures today through evolution; we humans are a product of evolution as well.

Reverse evolution also occurs in organisms when unfavorable mutation becomes a common phenomenon that can be inherited. This situation can also be called “degenerative evolution,” or “devolution.” Devolution will cause a species to be less adapted for survival and less suited to the environment, and they will usually go extinct after a period of struggle.

All species are evolving, and according to the theory of evolution, all creatures on Earth are descended from the same ancestor. Primitive life mutated differently in different environments, leading to the differentiation of animals, plants, and fungi. These life-forms continued to evolve; the strong survived, while the weak were eliminated in a process we call “natural selection” and “survival of the fittest.” It is also referred to as the law of natural selection; this is one of the most important laws in the theory of evolution.

Two: Reasons for Species Extinction

There are about 2,000,000 species of animals, 270,000 species of plants, and 35,000 species of microorganisms currently recorded, and scientists estimate the total number of biological species (recorded and unrecorded) in the world to be ten to thirty million. However, many more species have existed on Earth. We can almost be certain that the species on Earth today are less than 1 percent of the grand total, as over 99 percent have already gone extinct.

The extinction of Earth’s creatures in the past was mainly a result of natural forces. Life on Earth has existed for 4.28 billion years and gone through numerous extinctions, but life itself has never been interrupted. Since the Cambrian explosion, Earth’s creatures have experienced five major extinction events, the biggest of which was the Permian-Triassic extinction 250 million years ago. During this event, 90 percent of marine organisms and 75 percent of terrestrial life disappeared, yet many species were preserved. We know that since life began, Earth’s environment has never deteriorated so much that no creatures could survive; even during major extinction events, it was only certain creatures that could not adapt.

Through the study of species extinction, it can be concluded that extinction always results from one of these three factors:

1. Environmental Factors

Environmental factors are the changes in the natural environment that cause species’ extinction. The earth’s environment is affected by a variety of factors, like volcanoes, asteroid or comet collision, geomagnetism disappearance, and climate change—all of which change Earth’s environment significantly. Some organisms can readily adapt to changes in the environment, while others may evolve to suit the environment in a gradual process. These organisms survive. Any species that does not fit one of the above conditions will become extinct.

Environmental factors are the main factor in species extinction, especially large-scale extinction. Studies of the five major extinction events show that environmental factors were the main reason every time. It is easy to understand how environmental change leads to mass extinction. Most organisms are exposed to the natural environment and sensitive to environmental change; such changes will inevitably lead to adaption challenges. Dramatic changes in the environment are especially conducive to extinction.

2. Competition

Competition refers to the extinction caused by stronger species eliminating weaker species, or interdependent species reducing in conjunction. Competition also includes the extinction caused by intraspecific competition. Competition generally only leads to routine extinctions, not mass extinctions.

3. Devolution

Devolution refers to the adverse mutations a species might suffer when there are no environmental or other external factors that may affect the species. These adverse mutations are hereditary, leading to a devolution of the species as a whole.

Once the devolution of a species becomes an irreversible trend, it will become increasingly difficult for the species to survive. They will be continuously eliminated until the species goes extinct. Devolution usually leads to routine extinctions.

Three: Threats from Evolutionary Laws

Evolutionary laws act on all species, including humans. All species are subject to the ruthless laws of extinction, adapting, or going extinct accordingly. Does this mean that human beings might also become extinct from natural forces?

1. Threats to Humans from Environmental Factors

Most organisms are exposed to the elements and adapt to environmental changes in a very simple manner. If global temperatures drop, animals evolve thicker skin and longer fur; if global temperatures rise, animals evolve thinner skin and shorter fur. Those who cannot adapt this way face extinction.

Additionally, due to the food chain relationship between species, the extinction of one species will inevitably lead to the reduction or extinction of other species that prey on it. Since animals have no way to process their food apart from chewing, they cannot change inedible species into an edible food source. Though digestive systems can evolve, few species complete such evolution. Animals obtain food from nature; they cannot domesticate and breed food, so changes in nature will affect their food source significantly.

Humans are not in this situation because their intelligence has reached an absolute high ground, and humans have mastered far more advance technology. Humans interact with the natural environment in a completely different way.

Humans are no longer exposed in nature; we mastered the use of animal skins and fire tens of thousands of years ago. Today, things are even more optimistic; we can adjust to the outdoor temperature by changing clothes, and we can adjust to temperature indoors with heating and air conditioning. We can even design specialized clothing and work facilities for extreme temperatures.

In regard to the environment’s impact on human food sources, we have an unparalleled advantage over other animals. Millions of years ago, humans learned to crush shells with stones and eat the nuts. Later we learned to use fire to cook raw food. Ten thousand years ago, humans learned to domesticate poultry and plants, far surpassing other animals.

Today we have greenhouse vegetables and fruits to eat in winter; we can change the genes of crops to cultivate temperature-resistant, pest-resistant, disease-resistant crops; and we can breed all manners of livestock in all kinds of weather.

Humans are also an omnivorous species. Plants and animals—cooked or raw—are all suitable food sources for us. This makes it much easier for humans to solve the problem of food shortages when environmental changes occur.

Does this mean the environment does not have a decisive influence on mankind? Of course not. The previous sections of this chapter have outlined environmental impacts that may threaten humanity; however, an environmental threat that could lead to human extinction would be one that could completely collapse global ecology. It would be far beyond normal environ mental change. The nearest threat that would threaten human survival is the threat of the sun evolving into a red giant, but that is too far in the future to consider today.

2. Threats to Humans from Competition

Powerful dinosaurs once ruled the Earth. Let us use this to make a hypothesis: if dinosaurs and humans existed on Earth simultaneously today, which would dominate the other? I think the answer is clear—humans would dominate the huge dinosaurs, not the other way around.

An empty-handed man encountering a wolf in the wild will be torn to pieces, let alone if he comes across a dinosaur. However, humans as a group—especially highly intelligent humans who have mastered high-tech means—have unparalleled strength.

It is certain that no species on Earth could destroy the seven billion humans today through competition. From an evolutionary perspective, mankind would not allow any species to evolve enough to threaten human survival. Humans are completely capable of controlling plant and animal evolution on Earth—enough to ensure they never become threats to humanity. Microorganisms are the most difficult to control, as they are so small in size and vast in number, new viruses and bacteria can unexpectedly attack humans. Malignant infectious diseases are especially terrifying; however, the infectious disease control and treatment methods we possess today are enough to limit this threat within a certain range and prevent it from causing too much harm to humanity.

There are facts to support our capability. The Black Death of the Late Middle Ages killed half of Europe’s population, but Milan was saved from the catastrophe because the bishop of Milan ordered all patients, dead or alive, to be kept behind walls and buried. Later scientific development coined this effective method as isolation, and it is one of the most effective means to treat epidemics.

In 2003, a highly infectious and highly malignant infectious disease called SARS broke out in China. Due to the convenience of travel, this disease spread to more than thirty countries throughout the five continents in only two months. People were terrified of SARS; however, countries applied effective inspection and isolation methods and curbed its spread after only five or six months, even though there was no effective drug treatment. Ten thousand people were infected in the end, and the death toll was less than one thou sand. If this had happened one hundred years ago, the situation would have been much deadlier.

The antibiotics and drugs we now have are effective enough to treat most new diseases. Though our treatment of SARS was not especially effective, it was good enough to deal with the situation. We can be sure that although diseases brought on by microorganism evolution will cause some death and harm, the modern methods we have mastered can prevent them from destroying humanity.

3. Threats to Humans from Devolution

The devolution here refers to the devolution of human beings—that is, whether human beings will devolve due to irresistible genetic mutations resulting in extinction. For example, we might stop reproducing, or our intelligence may decrease until we become common animals, or some other type of devolution might occur.

According to the principle of evolution, the more an organ is used, the more it will evolve. Humans are the only creatures that use their brains to adapt to the environment; thus, humans’ brain capacity will only become more developed. In terms of creativity, human creativity has been steadily growing with no signs of stagnation or regression. As long as our intelligence does not devolve, humans are fully capable of dominating Earth and adapting to the environment continuously.

Even if humans did start devolving intellectually and physically in the future, the gene re-engineering technology we currently have would be enough to save ourselves after some development. Gene re-engineering refers to a technique that cuts, pastes, and repairs the genes on DNA using enzymes. This technology has already been widely used. Scientists can turn cotton red, yellow, or brown; they can produce seedless watermelon and seedless grapes; they can make frogs grow six eyes; and they can stop rats from growing tails. All this is the result of gene re-engineering.

If we wish to, humans can re-engineer their own genes in the near future. The Human Genome Project has conducted a comprehensive study and sequencing of the twenty thousand human DNA genes formed by three billion base pairs and has achieved considerable results. As biological science develops more in the near future, it is entirely possible that we will find out all about human genetic structures and genetic life codes. With a little more effort, humans will be able to freely re-engineer themselves.

We are pleased to see that current technology has succeeded in saving many endangered species. For example, British scientists have launched a plan to freeze and store the DNA of endangered species, and Chinese scientists have successfully cultivated the endangered yew tree and protected the endangered giant panda, Chinese alligator, crested ibis, and so on.

It is clear that any species mutation will not happen all at once. If we found signs of human devolution in the future, we would be fully capable of using bioengineering technology to prevent such adverse mutations, and we would have ample time to prepare for such an event. Therefore, devolution is not a factor that will lead to human extinction.

To sum up, if we use the sun’s evolution into a red giant in five billion years as a boundary, there are no factors in nature that will cause human extinction. In terms of natural chance, we have a long future ahead of us. This can also be proven through the survival of other species. Sixty-five million years ago, dinosaurs survived on Earth for 160 million years. Humans are stronger and smarter than dinosaurs and much more capable of adapting. It is only logical that humans will survive much longer than dinosaurs. Relative to the history of dinosaurs, we are yet in the infancy of our development. The idea that we have hundreds of millions of years ahead of us is just logical reasoning.

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