Our Bodies Are Warning Us
Lessons from millions of years of evolution
Edmond Alkaslassy
Almost none of us were alive in 1918 during the previous pandemic (the Spanish Flu) most comparable to the current one, so perhaps we should be cut some slack for being ill prepared.
Probably not. Numerous recent novel threats should have provided sufficient warning that the next one was coming soon. HIV killed millions, as did the flu pandemic of 1968 and the Asian flu in the 1950’s. Anyone old enough to vote has witnessed the emergence of several new infectious diseases: SARS (2002), H1N1 Swine Flu (2009), Ebola (2013), and Zika (2015). Instead of being caught off guard when new diseases arise we should always be expecting new ones to appear.
Some countries chose to learn from previous outbreaks. Taiwan made thorough preparations for future crises and acted quickly when the coronavirus emerged, limiting the damage to 462 cases of COVID-19 (19 cases/million) and seven deaths. Other countries did not prepare or respond as well. For example, the United States has roughly one quarter of the world’s COVID-19 cases (4,400,000 cases or 13,293 cases/million) and deaths (150,000) while comprising only 4.25% of the world’s population.
Preparing for future pandemics is a choice. Failing to prepare is also a choice, one with obvious and significant consequences. Perhaps citizens around the world will demand better preparations from their leaders in the future.
The US (and other countries) missed the warnings provided by recent outbreaks but also missed more cryptic and profound warnings: warnings hidden in our own bodies.
Our very DNA contains evidence that viruses have been infecting us for millennia. When the genetic material from a virus enters a human cell (in order to make more copies of the virus), sometimes that genetic material gets permanently recombined with the genetic material of the host. In other words viral DNA can become a permanent part of our own DNA, and that appears to have happened: studies show that roughly 8% of human DNA originated from viruses. The warning in our DNA is clear: viruses have been infecting us for a very long time and there is no reason to hope they will stop doing so.
Another internal warning comes from one of our organ systems: the immune system. But before we consider the immune system in particular let’s consider organ systems more generally.
The human body consists of several complex organ systems such as the respiratory system and the digestive system. Question: Why do we have organ systems? Consider the digestive system, a 30-foot long tube plus associated organs (teeth, salivary glands, gall bladder and more). Those elements are not just taking up space. This complex system performs the important function of breaking down food and distributing the energy and matter therein for use by all cells throughout the body. We require a digestive system to survive. And each of the other organ systems (e.g., respiratory, nervous, muscular) also performs specific and necessary functions.
All our complex tissues, organs and organ systems have been built and fine-tuned by natural selection for many millions of years. Individuals with more efficient organ systems had (have) a better chance of surviving and leaving offspring. Thus we have the answer to our question: We have organ systems because they improve our odds of surviving and reproducing.
Now let’s consider the immune system. The immune system provides vital protection against harmful infectious agents: viruses, bacteria, and other pathogens. It consists of a hodgepodge of widely dispersed organs including lymph nodes, thymus and spleen. These organs produce a diverse array of cells that protect us from infections and that “remember” previous invaders in order to respond to future infections more rapidly. They also produce chemicals that induce virus-killing fevers. Why do we have an immune system? (Hint: We’ve seen this answer before.) Because an immune system improves our chances of surviving and reproducing.
Humans are not alone in having an immune system. All vertebrate animals have immune systems of varying complexity. Invertebrate animals such as insects have immune systems, and plants too have immune systems.
Why are immune systems so widespread? Because plants and animals have been subject to harmful and potentially lethal attack by viruses, bacteria, and other pathogens for hundreds of millions of years, and those with better immune systems were more likely to survive and reproduce. Every day for those millions of years, selection favored every individual plant and animal on earth that was better able to resist those attacks. Individual plants and animals that could better defend themselves against microscopic intruders were more likely to survive and reproduce than those who were less able to defend themselves.
Organisms that exist in today’s world have immune systems (ranging from simple to highly complex) because their ancestors had immune systems that helped them survive, and that beneficial trait was passed on to their offspring. Put another way, plants and animals have survived to the present day at least in part because they inherited protective, functional immune systems.
It bears mentioning that none of our remarkable organ systems constitutes a promise of good health or long life. The presence of a digestive system does not guarantee that its owner will find sufficient food. Likewise, the presence of an immune system does not guarantee protection against all pathogens. Organisms have always been and will always be vulnerable to some pathogens. We are incredibly fortunate that there are now vaccines and antibiotics to protect us from some of the worst diseases. For example, before a vaccine was developed in 1796, half a billion people perished from Smallpox and as many or more were disfigured by it; now the disease has been eradicated. Vaccinations teach the immune system how to respond to dangerous viruses via exposure to dead or weakened versions of the virus. If we subsequently encounter the “live” virus we do not get sick or die because our immune system has already learned how to neutralize the threat. We do ourselves a favor by keeping our immune system strong via healthy diet and regular exercise, but our immune system is no guarantee of safety; vaccines provide a level of protection far beyond what the untutored immune system can offer.
The presence of any complex organ system tells us something vital about the organism and its evolutionary history. For example, the presence of a digestive system is evidence that the organism must eat to survive and that its ancestors have been eating for millions of years; complex organ systems do not form overnight. Similarly the fact that humans (and plants and other animals) have an immune system is evidence that we are currently under assault from microscopic attackers and that our ancestors have been fighting them off for millions of years. The presence of an immune system indicates that fighting infection has been and continues to be a routine and integral aspect of life on earth. Our immune system is a warning that novel infectious threats should be expected to emerge at any moment, as they have for millennia.
In the future we have the opportunity to heed a corporeal warning whose wisdom is millions of years in the making. The message is clear and compelling (albeit silent) and not subject to opinion or political debate. In hindsight, the warning implicit in our partially viral DNA and our complex immune system seems obvious.
Thanks to our relatively big brains we are very good at learning thus we have the potential to learn a critical lesson from recent epidemics and from our bodies: novel infections are a regular, dependable feature of our world, something to be expected. Let us hope that we do not ignore or forget that lesson again, and that we prepare better for the next outbreak.
But if we want to be better prepared for the next outbreak then we would do well to recognize our biological shortcomings. First, we should remember that although the immune system is a powerful tool it is not an ironclad guarantee of safety. We should not be complacent just because we may be in good health at the moment; instead we should always be alert to novel diseases (and take full advantage of vaccines). Second, primates (like us) are primarily oriented to visual stimuli. Viruses and other pathogens are not visible to the naked eye thus they represent an essentially invisible threat. Such threats do not grab our attention as viscerally as more visible threats (e.g., an avalanche or a lion) do. But these invisible threats can be deadly and we must try to keep them in mind, even though they are out of sight. Third, our brains are wired to pay attention to things that are happening now, not to prepare for events that will occur in the future. If there is a dangerous animal nearby then we run away immediately. Natural selection has favored individuals who noticed and reacted to events taking place over relatively short time frames. Natural selection simply has not favored long term planning in humans, thus our brains are not naturally wired to be concerned with the distant future.
But the human brain is an incredibly plastic organ that can adapt to diverse circumstances and learn all kinds of strange and difficult tricks with no direct evolutionary precedent, like playing the violin or designing a computer. We can do hard things when we are motivated to do them. Now that the coronavirus pandemic has our attention we are more motivated to heed the warnings around us and within us, and learn once and for all that novel diseases are a guaranteed part of our future. But learning is the easy part. The hard part is doing something that does not come naturally but that can be done, as the Taiwanese have proven: Planning ahead for an invisible threat that doesn’t exist yet.
Author biography: Edmond Alkaslassy taught biology for 21 years at Pacific University, Forest Grove, Oregon, and is writing a humorous book that compares human behavior to that of other animals.
