This paper takes part in the series essay competition of “great science” of Recordunkown.
The universe was born in the singularity big bang 13.8 billion years ago. After the big bang, the universe is expanding and forming various things, such as galaxies, stars, planets, rules of time and space, etc. In many things, the birth of life is the most magical and mysterious thing in the universe.
The earth was born 4.6 billion years ago. After hundreds of millions of years of evolution and stabilization, early life was born soon, about 3.8 billion years ago. After billions of years of evolution and evolution, human beings were born millions of years ago. After the birth of human beings, we often think about such a question: why can’t living things achieve immortality?
I believe many people have a dream of immortality. In ancient times, emperors such as Qin Shihuang and Li Shimin made all kinds of efforts to achieve immortality, but they all failed in the end. Although people all know that immortality is impossible, there are still more and more people who want to solve this huge mystery. Especially when human beings enter the era of science and technology, scientists expect to find the secret that life cannot live forever through the power of science and technology.
So, have scientists found the secret behind the fact that living things can’t live forever? Through the continuous exploration and research of life, scientists have found a part of the mystery that life can not live forever. The answer given by scientists shocked many people. Why? It turns out that through research, scientists found that immortality is the original attribute of life. But later, for some reasons, life gave up the attribute of immortality and developed in other directions. What’s the matter?
Through the research and exploration of gene level, scientists have finally found the key to affect the life of organisms, that is telomere. Telomere is a DNA sequence at the end of eukaryote chromosome that does not encode any protein. Every cell division will lose a small telomere. When the telomere length is less than the critical length, the cell will stop dividing, and the life body will go to aging and death.
I believe many friends know that the reason why organisms, including humans, can survive depends on metabolism, and the core of metabolism is the continuous division of cells. Organisms are composed of countless cells, which will continue to divide and renew. Only when new cells replace the old and dead cells, can life survive all the time. If cells no longer divide and renew, then life will come to an end.
The core of cell division and renewal is the telomere at the end of chromosome. The length of telomere will shorten with the increase of cell division. Some people may say that if we find the technology and method that can make telomeres no longer shorter, does it mean that organisms can live forever? This is true in theory, but the actual situation is basically impossible.
At present, the only cancer cells that scientists have found can achieve unlimited cell division, because the highly active telomerase in cancer cells can fill the telomeres lost due to cell division. However, because cancer cells can not differentiate into tissues and organs to participate in the construction of the body, its unlimited value-added will also capture the nutrients needed by normal cells, so the immortality of cancer cells is at the cost of the rapid death of the body.
After we finish talking about telomere, the core of cell division, let’s go back to the topic at the beginning of the article: why is immortality a primitive property of living things? We have to start with the earliest life on earth. About 3.8 billion years ago, the earth gave birth to early simple life. At this time, life was asexual. I believe many people have heard of asexual life and death and sexual reproduction.
Asexual reproduction is a kind of reproduction mode in which a new individual is directly produced by the mother without the combination of male and female germ cells. It is characterized by a very fast propagation speed, and can retain the role of good characters of female parent. The earliest life on earth is this kind of asexual life. With their rapid reproduction, the early life on earth develops very fast.
Some people may say that asexual reproduction does not mainly refer to the way of plant reproduction? According to the form of modern life, asexual reproduction is mainly reflected in plants, but it does not mean that it cannot be reflected in animals. The cloning technology that human beings have been exploring and studying is actually a way of asexual reproduction. It can be seen that if the early life on earth has been evolving in the form of asexual reproduction, the more complex organisms, including intelligent life, will also be the way of asexual reproduction.
And an important attribute of asexual reproduction is immortality. But why did early life give up asexual reproduction and evolve to sexual reproduction? In fact, it is mainly for the health and better continuation of life. As we all know, the direction of life evolution depends largely on the choice of nature. After drastic changes in nature, the direction of life evolution will be seriously affected.
The early asexual life in the earth after rapid mass reproduction, and finally triggered a dramatic change in the earth’s ecological environment, how is this going on? It started 3.8 billion years ago when primitive life first came into being, and lasted for 1.4 billion years. The earth’s environment did not change much. Archaea and eubacteria continue to divide and live carefree in shallow water.
However, 2.4 billion years ago, the oxygen produced by cyanobacteria began to accumulate in the atmosphere, which is the “Great Oxidation Event”. For anaerobic primitive life, oxygen is highly toxic. At the same time, oxygen consumed the greenhouse gas methane in the atmosphere, making the earth drop by 70 ℃ in tens of thousands of years, and the whole earth was frozen, which is the Huron ice age.
If life wants to continuously complete good evolution, it can’t do without a suitable temperature. If this asexual life is allowed to continue to develop, the earth will become a real frozen planet, and eventually life will be extinct. At this time, nature took decisive measures to force organisms to evolve from asexual to sexual reproduction, so that the earth gradually returned to a suitable temperature.
Although life gave up asexual reproduction and chose sexual reproduction for survival and the whole ecological environment of the earth, in the later evolution and evolution. The advantages of sexual reproduction are gradually reflected. One of the important advantages is the continuous optimization of genes, which makes life more and more high-quality and advanced.
The advantages of sexual reproduction in gene continuity are shown in the following three aspects. One is to combine two beneficial mutations in one individual, so that beneficial traits can be spread more widely. The other is to gather the two harmful mutations together to eliminate the harmful genes from the population more quickly. The third is to create new individuals more adaptable to the environment than the existing genotypes through gene recombination.
Sexual reproduction has been tested for a long time, which proves how correct it is for primitive life on earth to give up immortality and choose sexual reproduction. With the rapid development of human science and technology, gene technology will shine in the future. At that time, we can artificially interfere with sexual reproduction and eliminate some bad genomes, so as to produce healthier and more advantageous offspring.
Of course, asexual reproduction, a form of life extension, naturally has its own advantages. Although it is mainly reflected in plants by nature, asexual reproduction will flourish again with the continuous progress of cloning technology in the future. Of course, we don’t know what impact it will bring to the earth and human civilization at that time.
Guys, what’s your opinion on this? Welcome to leave a message below to discuss and express your opinions.