The House Select Subcommittee on the Coronavirus Pandemic published a "" in mid-July on the suppression of the lab leak hypothesis on COVID's origins. The only thing more problematic than the Subcommittee's conclusions from the hearing being exactly wrong, is the fact that the question of COVID's origins is still up for debate. The lack of any evidence other than supposition to support the lab leak origin hypothesis, as well as the extensive investigations by virologists of the virus's zoonotic origins, should have extinguished the controversy long ago. Here, I present an evolutionary angle to the argument -- one that supports the natural origins theory.
All scientific evidence supports the hypothesis that SARS-CoV-2, the virus that causes COVID, either emerged from or evolved in the Huanan Market of Wuhan, China. That evidence is substantial. It ranges from genomic (the famous "" paper and a ) to epidemiological and historic: as evolutionary biologist Michael Worobey, PhD, , the first COVID cases rose in and around the Huanan live wild animal market -- not around the Wuhan Institute of Virology laboratory, across a river and 10 miles away. the virus made a leap from animals to people in the market at least twice. And both traces of virus and DNA indicating the presence of the susceptible species known as "raccoon dogs" on the cages in the live wild animal section of the market.
There is neither evidence nor logic backing up the lab leak hypothesis. There is only supposition, unsupported by science, bolstered by politics alone.
Where the pathogen originated is only part of the question. Equally important is understanding how. How does a novel pathogen emerge and adapt to a new host species? This an evolutionary question. It requires an evolutionary answer: The key to adaptation lies in spread.
Viruses adapt to a new host population by spreading among that population. If a novel virus isn't slightly transmissible to start with, it will never evolve into an established pathogen. Once a new germ starts transmitting, even sluggishly, natural selection will exert enormous pressure on transmission, because only the strains that transmit persist and prevail.
SARS-CoV-2 is a master at transmission. Over 3.5 years, the virus has evolved ever-greater transmissibility. The world has been the virus's natural laboratory, and the virus continues to evolve and adapt. Could this process of "just-good-enough" initial transmission have started in a laboratory? To deliberately engineer a transmissible virus using "gain of function" experiments, a scientist first must figure out the genetic riddle of transmission. How does a virus move from host to host? We know how SARS-CoV-2 infects: its spike protein adheres to human ACE2 receptors and pries them open to infect airway cells. You could engineer a virus to infect human cells -- Ralph Baric, PhD, and his team in North Carolina did exactly that, through genetic manipulation and serial passage a coronavirus that infected human airway cells.
There's no reason to think that Baric's wimpy virus, engineered and used only to infect cells, had the ability to spread. Transmission is a complicated process. As retired immunologist and drug development expert Richard Kirsch, PhD, put it when I emailed with him, "The virus needs to aerosolize, survive in airstream shear forces, avoid desiccation, remain suspended, and maintain infectiousness." It's one thing to infect human cells, quite another to get shed by one host and picked up by another.
While scientists know something about the genetics of infectivity, no one thoroughly understands the genetics of transmission. We know that if a germ has any ability at all to transmit (however weakly), natural selection will push for greater and greater transmissibility, because more transmissible strains will outcompete the less effective spreaders. We've seen that with the constant evolution of SARS-CoV-2 variants over the last 3.5 years, moving towards greater transmissibility.
But let's suppose that Shi Zhengli, PhD, bat virus expert at the Wuhan Institute of Virology (WIV), and her team either fiddled with a natural bat virus or engineered SARS-CoV-2's predecessor, blindly landing on a just-barely-transmissible genome. That's only the first step. To make a truly human-adapted virus requires people, many people, just as a mink-adapted virus (as happened later in mink farms), requires many minks. A crowded laboratory building might well be as effective a viral hothouse as an indoor market.
But first, someone would have had to catch the novel strain and spread it to other people: virologists, staff, secretaries, janitors; friends, families. SARS-CoV-2 often spreads asymptomatically. But as it burned outward from its point of origin, the human wreckage it left behind would have been unmistakable. COVID-19 from the onset has been, and often remains, a virulent disease that would not have been lost among the respiratory sniffles and fevers of the winter season.
The sick and the dead wouldn't have clustered around the Huanan market. They'd have been at the epicenter of the outbreak -- the WIV and its surroundings, as SARS-CoV-2 began its dance, growing fitter and more adapted, mastering its hold on its new host population as it spread. That three scientists may have contracted an unidentified respiratory illness in December 2019 only proves the point: if their infection had actually been newly-created COVID-19, far more people in their vicinity would have caught it, spread it, even died of it.
That didn't happen. The pattern is clear, as Worobey, et al., have shown. SARS-CoV-2 moved outward from the Huanan market, jumping at least twice into humans as it moved among crowded animal stalls, infecting keepers and customers, evolving more efficient human adaptation as it broke out of Wuhan and mowed across the world, burning up countless millions in its path, remaining a virulent disease even as it more and more effectively spread.
It's the initial outbreak that tells us what we need to know. The epicenter of viral spread was the market, not the lab.
If it were otherwise, every virologist on the planet would have told you so.
is an anthropologist and science writer, having covered biological weapons and the evolution of infectious disease for over 25 years.