Why do humans get cancer? Is cancer a legacy of evolution?

Why do people get cancer? We can explain it from the perspective of evolution.

Before that, let's answer a question: Is the theory of evolution we are talking about today the theory of evolution proposed by Darwin? Actually, it is not. Because when Darwin proposed the theory of evolution in the 19th century, the disciplines of genetics, cytology, taxonomy, etc. were not well developed. Therefore, Darwin's theory of evolution lacked many theoretical foundations. However, with the development of science and the gradual confirmation of other disciplines, the correctness of the theory of evolution was finally established.

Between 1936 and 1947, many branches of biology merged, and knowledge such as Darwin's theory of evolution and Mendel's laws of genetics were combined to form what we call the Modern Evolutionary Synthesis today.

According to the modern evolutionary synthesis, the evolution process occurs in this way: biological individuals need to develop and metabolize, which requires the production of new cells. In the process of producing new cells, genetic information will naturally be replicated. However, the replication process cannot be 100% accurate, and there will inevitably be a small number of errors, which are mutations at the gene level.

Although these mutations will occur, the organism itself has the function of error correction, and most of the mutated cells are eliminated by the organism itself. Those that are retained may bring new characteristics to the organism. The following process is just as Darwin described, the fittest survive, and mutations that can adapt to the environment will be retained, while mutations that cannot adapt to the environment will be ruthlessly eliminated.

Looking back at this process, we can clearly see that errors will occur during the replication of genetic information, and some of these errors will turn cells into cancer cells. Although our own immune system will try its best to eliminate these bad mutations, there will inevitably be some that slip through the net, and those that slip through the net will gradually evolve and develop into cancer that endangers our health and life.

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In short, the evolutionary process is a natural law that is inevitable, so the occurrence of cancer is also inevitable to some extent. Whether it is a human or other organism, as long as they live long enough and the process of genetic information replication in their bodies occurs enough, they will definitely face cancer.

Therefore, the occurrence of cancer is closely related to the life span of an organism. We may ask, when we talk about cancer-inducing factors, we often think of external stimuli such as smoking, drinking, and chewing betel nuts. Now it seems that the occurrence of cancer is more closely related to age. Are there any contradictions between these statements? In fact, there is no contradiction.

As we mentioned earlier, problems in the replication of genetic information can lead to cancer, and behaviors such as smoking, drinking, and chewing betel nuts can stimulate cells and increase the risk of cancer. The older you are, the more likely you are to make mistakes during long-term replication, so the view that "cancer is closely related to age" that I just mentioned does not conflict with this point.

In short, from the perspective of evolution, cancer is a disease that organisms must face in the process of evolution. Starting from this point of view, it can help us understand many things. For example, some people believe that in modern society, although the level of medicine has advanced by leaps and bounds, the incidence of cancer is getting higher and higher, and they think this is a failure of medicine.

But the opposite is true. It is precisely because of the rapid progress of medical technology that many diseases do not lead to death and the average life expectancy has increased significantly that this situation has occurred. In layman's terms, it is because of medical progress that we can live to the age of cancer. And although many cancers cannot be completely cured at present, doctors have never stopped researching in this area.

The article is produced by Science Popularization China-Starry Sky Project (Creation and Cultivation). Please indicate the source when reprinting.

Author: Sun Yifei, Director of the Medical Education History Research Office, Hebei Medical University

Reviewer: Chen Gang, deputy chief physician, Peking Union Medical College Hospital