We started the month with another special participation here on the blog. This time the author of the guest contribution is Professor Milton Groppo, coordinator of the Graduate Program in Comparative Biology at the Department of Biology of the USP in Ribeirão Preto. He explains how the emergence of Covid-19 opens a window to understanding the evolutionary process in real time. To find out more, just read his text below.
The Covid-19 pandemic caused by Sars-CoV-2 (technical name for a type of coronavirus) has been going on for over a year. The deaths and overcrowded intensive care units, the discussion of restrictive measures, hygiene measures, which mask is the best, which vaccine is best suited, agglomeration or not and everything that has to do with Covid has dominated the news in all media worldwide.
Since Covid-19 is literally a matter of life and death, it is only natural for this to happen. But, unnoticed by a large part of the public, another story unfolds, a story that many people deny and do not understand: biological evolution that is currently being broadcast live on every television channel we have called.
Biological evolution is nothing more than the transformation process that organisms go through or present on our planet over the course of time. The existence of fossils of plants, animals, and even microorganisms, beings that no longer exist, is a great way to show how the amount of organisms has changed on Earth over millions of years. The distinct existence of species more similar than others in both shape and development suggested a history of changes these species have undergone from a common ancestor.
Only in the last 150 years have hypotheses based on scientific data developed mechanisms that explain the change of species over time – such as the natural selection of Darwin and Wallace or the idea of a neutral mutation. However, nowadays it is known that evolution is only possible when there are variations in the organisms, variations caused by mutations in genetic material (DNA or RNA). Since changes in organisms are slower than the human eye can perceive, because they are processes that take thousands or millions of years to perceive, it is difficult to see evolution at work.
This is a point that favors the deniers of biological evolution. However, if we take a closer look at what is happening now to the Covid-19 pandemic and its causative agent, we will see that we all have the elements to show that biological evolution is a fact and is happening now.
It is a very close relative of another virus, Sars-CoV or Sars-CoV-1, that caused an outbreak of infected humans in humans a few years ago (between 2002 and 2004). The acronym Sars denotes the causative agent of the “severe acute respiratory syndrome”. They are both part of a “family” of RNA viruses that cause infections in various organisms such as birds and bats.
Sars-CoV and Sars-CoV-2 are similar and share about 80% of their genetic material (more details here). In addition, about 96% of the Sars-CoV-2 genetic code is the same as that of other coronaviruses that infect bats. It is believed that these animals transmitted such viruses to another intermediate animal and then to humans, or that the transmission occurred directly.
Like all viruses, they are simple units that are formed by a DNA or RNA molecule (in the case of retroviruses such as influenza viruses or in Sars-CoV) and are often protected by a shell made up of proteins and fats. In the case of Sars-CoV, that cover has numerous spikes (“spikes” in English) that help viruses attach to the cells that will infect them – as if they were ticks clinging to our clothes. These spines are found throughout the coronavirus family.
Viruses cannot multiply without penetrating (= infecting) the cells of another organism because they need the machinery of the infected cell to produce new copies of themselves. So there is even a discussion about whether or not they are living beings. Another characteristic of viruses (including Sars-CoV) is their specificity, which means that a pathogenic (i.e., disease-causing) virus for plants does not necessarily apply to humans. That is why there are canine flu viruses that do not cause influenza in humans and vice versa.
But where does evolution come from in this story?
As Covid-19 emerged and spread, in addition to the terms mentioned at the beginning of this text, social isolation, masks, treatments … other words emerged such as “lineages” or “variants” – variants of the United Kingdom. South Africa, Brazil (with the P1 variant first detected in Manaus), now a possible new variant in India that would contain a “double mutation”. But what are these variants? How did they come about? Have they always existed? And mutation? And what does evolution have to do with it?
We may have doubts that, despite all their similarities to the human species, chimpanzees and gorillas are our relatives and share a common recent evolutionary history. We do not see events of lineage differentiation of these organisms as happened millions of years ago. Furthermore, lineage differentiation was slow and we would not perceive it with human eyes even if we stepped into a time machine.
Another fact that might speak against the notion that chimpanzees, gorillas, and humans share a common ancestor is that the differences between these species are clear today and if we didn’t have intermediate fossils (which we have today) we might think that such species would do so. They were not created by gradual transformation, but would have been created as they are today.
In the case of the virus that causes Covid-19, we have seen the changes happen quickly, with new strains forming at very short intervals of months. A few years ago we had no news from Sars-CoV as coronaviruses have been found in other non-human organisms such as birds and bats. The fact that these viruses have recently acquired the ability to infect humans is related to variations that occur in the populations of these viruses.
Like us humans, every virus is an individual and they have genetic differences. These genetic differences or variations are caused by mutations in DNA or RNA. Mutations are the source of variability in different species and, if set (or selected), can lead to changes in populations over time – that is, they can promote evolution. In contrast to “large” organisms, viruses have a very fast life cycle, sometimes of a few hours, and produce a stratospheric number of copies of themselves in a very short time.
Mutations occur in all organisms and are the basis for the variation they represent. But mutations are not all bad or all good: most are neutral and have no immediate effect on a population. In addition, organisms with the longest life cycle (such as a human, elephant, or redwood tree that lives hundreds or even thousands of years) are less likely to have mutations over time than the mutations identified in the study a role of evolution are those that are passed on to other generations.
And this is where the leap lies with viruses: because they multiply quickly, there is a much greater likelihood of mutations occurring over time that can be passed on to other generations. And when more mutations appear, there is a greater chance of a mutation that allows that strain (or line) to infect organisms other than those that have already infected that type of virus.
It was probably what happened in China or elsewhere at the beginning of it all: in one place, there happened to be a coronavirus line that infected another organism (probably a bat) and contained a mutation that made it possible for that specific line to Infecting people, then called Sars-CoV. The viruses that caused Covid-19 did not “believe” that it was better to infect humans; It was a fortuitous event, but was facilitated by the contact between humans and other animals (through creation and / or consumption).
We then see that mutations that caused variations in Sars-CoV led to the most recent infection of these viruses in humans, events that were not recorded before the 2000s. This in itself shows how evolution takes place. But the story doesn’t stop there. After Sars-CoV-2 infected people and caused Covid-19, other mutations associated with this virus were discovered in certain geographic areas during 2020: the UK, South Africa, Brazil, such as the infamous P1, all of this in less than a year.
These strains, or strains that have new mutations, have differences in the configuration of proteins in the thorn-like protrusions that appear in the outer protective layer. With the change in the shape of these spines, the immune system recognition of the infected organism is impaired or even prevented, and the immune system’s response is not fast enough. Since vaccines work either with attenuated strains of virus or with RNA recognition, mutations that cause changes in the spines or other parts of the virus barrier are viewed with great concern as they can render vaccines ineffective.
The new variants exist alongside strains that have not undergone any mutations that change the shape of the spines of the protective layer. These variants compete with each other for hosts (remembered Darwin?) In a process of natural selection, where the variant best adapted to a particular condition can increase its representativeness in a virus population.
And the longer the pandemic lasts, the greater the likelihood of Sars-CoV-2 mutations appearing and fixing changes in pathogenesis and virulence like the Manaus P1 mentioned above, which may be more contagious for people younger and without and more dangerous is comorbidities. In other words, the more time passes, the greater the likelihood that more variations will occur – that is, new mutations that can be fixed in virus populations, and the likelihood that new variants will form. In other words, more chances of … evolution!
The emergence of Sars-Cov-2 and new variants is noteworthy as they have a direct impact on human health due to Covid-19, which is understandable given that it is a matter of human life or death. However, the mechanisms of mutation and fixation of these mutations in different variants of viruses, the ability of new variants to infect other organisms with new adaptations, and the phenomenon of competition between different variants are no different from the changes and adaptations that we could indirectly in observe all organisms that have existed on earth for millions of years.
It’s a biological evolution that happens in real time within the range of a cell phone or remote control. Along with the pressing medical problem, this is an excellent opportunity to show that biological evolution is a fact and that this fact can no longer be ignored by groups that deny science. Though painful, it is another chance to learn.