So far this year, over 180,000 people have died from COVID-19, including 48,000 Americans. Including my grandmother. Perhaps including someone you knew and loved. In the broad sense, this is nothing new. The story of our species, in fact the story of multicellular life on Earth, has been first and foremost one of battle against infectious disease. There have always been victims. The fittest survive. Germs have shaped our evolution and made us who we are. And yet. None of that is very comforting when you experience it firsthand. For all that I’m fascinated by natural selection, I don’t want it anywhere near my family.
You probably already know more about coronaviruses than the average biologist did six months ago. But just in case, here are a few details. SARS-CoV-2 is a virus that first infected humans at the end of last year, in China. “Coronavirus” is a general term for this family of viruses. This specific coronavirus causes a disease called COVID-19 which can feature severe symptoms including fatal lung failure. SARS-CoV-2 is descended from viruses that naturally infect other species like bats. It was not deliberately engineered. It may have jumped species through the exotic meat trade. However, there’s no reason to think that Chinese culture or cuisine is particularly germy or prone to these transmissions. All over the world, humans are penetrating wild spaces and wild microbiomes and collecting unwanted souvenirs. Viruses are not technically alive and can’t be killed by antibiotics or other drugs. Like all viral diseases such as the flu, measles, rabies, or AIDS, the best thing you can do to stay safe is to avoid direct exposure to the virus. For SARS-CoV-2, that means minimizing contact with people who might be infected (i.e. potentially anyone at this point) and washing your hands frequently, especially after touching surfaces that others regularly touch. Our second-best defense against viruses is vaccination. We don’t have a vaccine for SARS-CoV-2, but scientists are working on it. Our third-best defense is antiviral drugs, which don’t exactly destroy the virus but reduce its impact and give the immune system more of a fighting chance. Again, we don’t have many treatments for this particular disease, but new developments are underway. Until we know more about this virus and have more tools to fight it, we all need to close our doors and stay isolated.
Pestilence has always been part of the human experience. Human genes that interact with pathogens often show signatures of natural selection. The CCR5 deletion conveys resistance to HIV and was infamously botched in the unethical creation of the first genetically-engineered humans. It may have been selected for by the Black Death. Malaria alone has driven several of the most pronounced adaptive differences among human populations. Viruses have caused changes all over our genomes. And COVID-19 can compete with the big boys in terms of impact. While naive optimists have compared it to the flu, it has already killed far more people than the flu’s annual toll. It hasn’t surpassed malaria’s yearly 400,000 yet, nor AIDS’ yearly 770,000, but it’s on track to do so. If we don’t keep it under control, it could easily kill more people globally in 2020 than all other infectious diseases combined.
Given the looming bloodbath, you might suppose that this is another epic round of natural selection, like the Black Death was. But it’s not. COVID-19 will have almost no effect on human evolution. Most of the people who die are elderly, and nearly all of post-reproductive age. Kids are almost universally immune, while teens and young adults are nearly so. So yes, we are witnessing survival of the fittest in real time. But to complete its task, natural selection needs to act when your future still potentially involves parenthood. That makes COVID-19 different from the various scourges that have shaped our DNA. A pandemic like this could hit our species every generation and we would not genetically adapt to it. Every wave would be just as bad. If it had spread among our ancient ancestors before they were writing down history, we wouldn’t have any evidence it had ever happened. It might feel scary to think that evolution can’t provide us with any weapons against this new threat. But really, this is a lucky scenario. For one thing, it’s an immense blessing that young people are largely immune. No matter how bad it gets, the pandemic isn’t the end of the world. For another thing, we don’t actually want natural selection to be making gross adjustments to our genomes. Evolution never stops, but it’s unpleasant when it acts quickly. Hastily constructed new defenses are kludges that carry costs. And finally, evolution already has, almost certainly, provided us with adaptive genetic diversity to resist COVID-19. While the human gene pool is paltry overall, our immune system genes retain the most functional variation. We are in a constant coevolutionary war against infection, in which genetic differences are frequently beneficial. Even if COVID-19 itself hasn’t been a selective agent, mutations that previously thwarted other microbes may be useful again. After all, HIV is not the reason for the CCR5 deletion, but it is the reason it’s become a handy genotype to have today. Some humans will inevitably turn out to have genetic immunity to COVID-19, even without previous exposure. We know that many folks don’t get sick. It remains to be seen if this resistance is innate, or if some can’t even transmit the virus. Already there are claims of specific genetic variants associated with COVID-19 resistance. These studies have been quick and cursory and merit a hearty degree of skepticism, but in a few months we’ll have more solid data. Epidemiological models that assume everyone is equally susceptible could be oversimplified. That’s good news. Of course, a few resistant individuals won’t change the overall trajectory, and all the shutdowns are absolutely still necessary. Our genetics would just mitigate the final death count. And the bigger point is, for all that COVID-19 has upended our society, it can’t touch our biological legacy.
This isn’t like the plagues of the past in terms of evolution. But how about in terms of emotion? In many ways, this is what natural selection feels like. It’s heartbreaking. Grief over the loss of loved ones. Fear and uncertainty about the future. Guilty relief when a good friend survives, even while you know others are perishing. My grandma was a fearless pilot and world traveler, a puzzle-hungry gamer, a master in the kitchen, and a loving matriarch to twenty-five descendants so far. A stoic survivor of everything from the Great Depression to cancer, she worked hard to provide a warm and welcoming presence to all, and thus found satisfaction. She ensured that everyone in her circle felt connected. She regularly mailed us letters and packages, even the local comics pages, when we were thousands of miles away. She lived a full and successful life. She had been nearing the end of it, coronavirus or not, and I believe she had accepted that. But loss is always sad. I’ll never again receive one of her homemade birthday cards or play Scrabble with her. More poignant still is the evanescence of a mind and memory that knew me and many of my relatives from birth, a link to my past and provenance. What has been especially difficult during this crisis is that no one in my family could be physically present with her as she declined, or gather in mourning after she passed. We shed tears alone in empty rooms. As this virus conquers the globe, my experience is far from unique. The modern world is getting a taste of the red and toothy side of nature.
Meanwhile, nature is getting a taste of the communal human spirit. It turns out that it’s not so easy to be a human virus. Most of us aren’t behaving like mere self-serving DNA replicators, heedless of the suffering of others. Most people are willingly taking on huge inconveniences just to block a disease that isn’t even a major risk to them personally. Holed up in our homes, we are reaching out electronically and maintaining a supportive community. We can see the bigger picture and serve our whole species, not just our own lineage. We can beat evolution at its own game. The path to victory is simply to test extensively for infection, open and close institutions strategically based on those results, and continue to work toward vaccines and medical therapies. This war is ours to win. And when we fail to take sensible precautions and people die, those battles are our losses. A pandemic not just an inevitable natural disaster, but a human-generated one. There have certainly been some stupid decisions that got us to this point. But the larger lesson from the past couple of months is that we are mostly a species of heroes. Just like my grandma, many of us will sacrifice our time and sweat with minimal complaint to provide the best possible life for those around us.
COVID-19 is history in the making. A collective horror that will define this era in our shared memories, like JFK’s assassination or 9/11. But still, there’s a reasonable chance that this won’t even be the worst pandemic of your lifetime. The conditions that allowed SARS-CoV-2 to emerge aren’t going away anytime soon. We’re still a globally-interconnected mass of human flesh, heavier than the Great Wall of China, encroaching upon wildlife on all sides. A perfect viral niche. If the next outbreak is actually a real nightmare, the kind that kills kids, how will we respond? I think we will be grateful for having had the chance to practice with COVID-19. I think we will be much more prepared, and unwilling to tolerate lollygagging. Over the next few years, I predict we will wisely invest in backup medical supplies, widespread surveillance, and basic infectious disease research. Furthermore, I think we will all draw hope from the way so many have risen to the challenge of SARS-CoV-2. Aided by technology, we can quickly assemble a support network. My grandma did it through the post office, and it’s even easier to stay connected through Zoom and social media. Nature doesn’t have to call all of the shots anymore. The choice is ours.