Toxins, Disease, and the Immune System Are All Evolving
The theory of evolution was proposed by Darwin. All things in nature are, at every moment, undergoing evolution visible or invisible to our eyes. As long as there is pressure of natural selection, there is evolution. For example, when a goshawk hunts a rabbit, the goshawk not only has talons the rabbit cannot withstand but also the advantage of vision; soaring high in the sky, it sees the ground clearly and easily spots where the rabbit hides. So in the food chain, the goshawk stands upstream. Facing the goshawk's threat, the rabbit is under survival pressure; under this pressure the rabbit has developed a certain intelligence. When the rabbit knows it cannot escape the goshawk's strike, it plays dead to lull the hawk; when the careless hawk approaches, it kicks out unexpectedly to attack, hoping to escape. This rabbit intelligence developed under the pressure of natural selection.
Evolution cares only about reproduction. Many of us may think that high social status and wealth mean success. But from a biological standpoint, the mark of human success is survival and the ability to reproduce. If one person has high education and social standing and is rolling in wealth but has no children or very few, while another is destitute but has many children, then from an evolutionary standpoint the destitute person with many children is the successful one, because his genes have been passed on; this is the numerical success of the genes. The greatest drive of any gene is reproduction; the British scientist Richard Dawkins made this crystal clear in his best-known work, The Selfish Gene.
Toxinologists believe that the earliest toxins also evolved in the process of natural selection. Most toxins come from subtle changes and duplications in the genes of biological immune systems, changes inherited by their descendants. The reason organisms' immune systems undergo these changes is chiefly to repel infectious diseases or microorganisms. From this angle it is not hard to understand why so many natural poisons can be used to treat human disease. But once a toxin arises, it is not limited to repelling infectious diseases or microorganisms; it can also harm other organisms. The enzymes that break down bacterial cell walls, for instance, also produce bioactive esters that control the switches of nerve cells; the proteins that tear apart foreign parasites can also tear the flesh of victims. So over time, some venomous animals used the enzymes and proteins they possessed to harm other organisms, in order to avoid being killed or to prey on others.
But evolution in the living world never rests. The animals hunted by venomous animals also evolve genes that defend against the toxins these predators carry. For example, snakes hunt rats, but some rats have, in the course of evolution, developed genes that resist snake venom, so they are not afraid of snakes. To survive, snakes must further evolve more toxic proteins and enzymes, so snake venom is also evolving. This kind of evolution is widespread in nature and never stops for a moment.
The bacteria, viruses, toxins, and cancer cells that cause human disease are also constantly evolving.
After antibiotics were invented, humans once thought they could defeat bacteria. But in recent years, with the emergence of "superbugs," humanity has realized that in the process of fighting bacteria, bacteria are also evolving. These superbugs, which emerged in evolution, no longer fear the antibiotics humans invented, and they easily take the lives of some patients they infect.
Viruses are the same. When we fight viruses, the viruses are also looking for ways to "adapt" to us. So when humans use isolation to deal with infectious disease, the transmissibility of the disease grows stronger and stronger, because viral genes are also "selfish genes"; like us, they must survive and reproduce.
Cancer cells are the same. Humans invent drugs to wipe out cancer cells, but the selfish cancer cells also constantly adapt to the various anti-cancer drugs humans invent, constantly mutating into daughter cells with ever stronger adaptability. So anti-cancer drugs always begin to show resistance after a period of use. This is also why I keep changing patients' medication regimens—I change my formula every fortnight; if I did not, patients would quickly develop resistance. From this angle, no prescription can solve cancer once and for all.
But humans are not lambs waiting to be slaughtered; our immune system is also constantly evolving. Our immune system is much like a computer operating system, constantly patching itself and upgrading. Each time a new virus or toxin attacks humans, the bodies of those who were infected and survived retain fragments of the virus or toxin as "memory." The next time the same virus or toxin attacks us, our immune system quickly recognizes it and repels it. So more than half the genes in the human genome are these kinds of "memory fragments," used to prevent disease.
We may often hear stories of cancer patients mysteriously healing on their own—such spontaneous remissions are more common in young children. These stories are not false; after cancer appears, these patients' bodies, drawing on the power of evolution, produced genes that act against cancer cells, so their cancer mysteriously "self-healed." The reason young children "self-heal" more easily is also that the child's immune system has not fully developed; as they grow, their immune system grows stronger, so patients who develop cancer in early childhood are more likely to recover. Theoretically, if more and more such "self-healing" cancer patients appear and reproduce many descendants, their genetic advantage will gradually change the spectrum of human disease; after a long evolutionary process, humans may no longer fear cancer. But whether nature endorses this human reasoning is up to fate. Evolution is often highly random and hard to predict.
The above views follow the ideas of evolutionary medicine. Since 1991, when the American physicians Randolph M. Nesse and George C. Williams proposed the concept of evolutionary medicine, introducing Darwinian evolution into medical research, evolutionary medicine has, over the past thirty-plus years, exerted enormous influence on anthropology, biology, and medicine. Though medical schools still do not teach evolutionary medicine theory to students, the technological changes triggered by evolutionary medicine's ideas are thriving in biopharmaceuticals.
We can take nature as our teacher and draw inspiration from the evolutionary history of living things—especially animals—to find good medicines. For example, the reason leeches can suck blood is that they contain an anticoagulant called hirudin, which prevents an animal's platelets from clotting normally, so that they can suck blood from their prey. In the process, hirudin is of course harmful, but for patients with thrombi in their bodies, such an anticoagulant is a healing medicine; so hirudin is now developed into an anticoagulant used clinically.
The first person to use the leech's anticoagulant effect to treat disease is unknown, but what we do know is that leech is a commonly used TCM medicinal. In the "Didang Tang" and "Didang Wan" of Zhang Zhongjing's Shanghan Lun of the Han Dynasty, leech is the chief medicinal. And this formula works better than using leech alone, because ancient Chinese physicians discovered more than one anticoagulant; they combined various anticoagulants into a formula that activates blood and resolves stasis, then added medicines like rhubarb that promote the excretion of static blood to clear it from the body quickly. The effect is faster—this is a very sophisticated means of treating disease.
Zhang Zhongjing of course could not, like a modern scientist, interpret his medical thought through evolutionary medicine theory, but this treatment experience is still highly effective today. This shows that our human ancestors, in fighting disease, were already unconsciously using the techniques of evolutionary medicine. These experiences are worth digging out for the treatment of human disease.