- Life on earth has always been about species struggling to secure their odds of survival. A little known story, though, is the complex role that viruses have played in our evolution.
- Today, these microscopic bugs are among our biggest threats, especially the zoonotic kind like the novel coronavirus. We must constantly adapt to stay a step ahead of them.
Twenty years ago, Matt Ridley’s The Red Queen, a brilliant and seamy proposition of how human behaviour has evolved in order to help protect the survival of our species. Ridley theorizes, with support from every corner of the animal kingdom—from water fleas to aphids, from guppies to peacocks and from cockerels to chimpanzees—that human beings are locked in a race for survival like Lewis Carroll’s character, the Red Queen.
To enhance their chance of survival, for instance, some bamboos flower only once every 121 years simultaneously worldwide and then die, killing their parasites with them. Female red finches choose the reddest male on offer as he is genetically more disease-resistant. The earliest civilizations were all ruled by emperors with large harems of women whose fertility was carefully observed, controlled and managed for the reproductive prolificity of their ruler.
Indeed, as we progressed from the paleolithic age, foraging for lean meats and berries, we randomly or intentionally (the verdict is still out) cultivated crops. The seed of civilization was planted. This is not a new theory and has been espoused by many, but Jared Diamond popularized this narrative for the lay person most strikingly if sensationally in his runaway 1997 success of a book, Guns, Germs and Steel.
As human beings settled down to an agricultural life with food aplenty, they domesticated animals. Living in groups of large human settlements resulted in the transmission of viruses such as smallpox, measles and influenza from domesticated animals to us. The Old World, having periodically been ravaged by these diseases from time immemorial (smallpox has been found in Egyptian mummies), was largely conferred immunity, unlike New World populations that were decimated by these infections after Europeans landed on their shores.
So then, what does evolutionary biology tell us about viruses? As Carl Zimmer puts it, we are literally living on A Planet of Viruses. For one, human beings are greatly outnumbered by them. The ocean alone holds viruses that would extend for 42 million light years if they were all in a line.
Viruses are also much older than us. In a cave in Mexico, 26 million year-old crystals were found to be teeming with viruses. Above all, we have been shaped by them. About 8% of our DNA consists of endogenous retroviruses.
A retrovirus called ERV-L that lurks in our genome dates back to 100 million years ago, and is now found in armadillos, elephants, manatees and humans. Another such virus called HERV-W actually makes syncytin, a protein critical to providing nutrition in the placenta. When it first infected the common ancestor of mammals, it was possibly responsible for evolving the very first placenta.
While this paints a somewhat rosy picture of our symbiotic relationship with viruses, the truth is less rosy. Viruses are our greatest existential threat, with smallpox killing close to 300 million people, measles 200 million and polio around 25 million people in the 20th century alone. Influenza, HIV, Ebola, SARS, MERS, H1N1 and of course SARS-COV2 are just a few of the viruses that have plagued us.
Staggering advances in science have led to vaccines and treatments for many of these. The past year has been a testament to the astonishing success of human beings to rapidly decode the genome and produce multiple vaccines for SARS-COV2.
But as our population continues to grow, and as we brush up against and further encroach upon the habitats of every other species, novel viral epidemics are going to become more common. Unlike smallpox and polio, these so-called zoonotic diseases are virtually impossibly to eradicate as they can be borne by other species.
As David Quammen, author of Spillover, writes of zoonotic diseases: “Ecological circumstance provides opportunity for spillover. Evolution seizes opportunity, explores possibilities, and helps convert spillovers to pandemics.”
As we ponder our fate in 2021, we would do well to think of our evolutionary history and the principles of the Red Queen. We may have evolved into apes with large brains, but we somehow seem blissfully unaware of our fate. Those who don’t adapt will not survive. And those who do adapt may find it takes “all the running you can do to keep in the same place”.