New York —
David Enard, associate professor at the University of Arizona, searches DNA for adaptation processes that were triggered by past epidemics
“It is like an arms race,” he says. David Enard, Associate Professor in the Department of Ecology and Evolutionary Biology at the University of Arizona, referring to our constant struggle to adapt to the threat of new viruses.
Enard and his laboratory team are dedicated to searching the human genomes for evidence of what were ancient epidemics.
And is that in thousands of years of evolution, there is much that can be found in our DNA.
“Are they adaptation episodes that were unleashed during different epidemics that occurred in the past ”, the expert tells BBC Mundo.
“The way we can see those adaptation processes in the DNA of people today is by looking at the differences in DNA between different human populations or even differences between the human genomes and those of other species.”
By analyzing them, he points out, it is possible to see where an adaptation process occurred in the genomes and “connect some of those adaptations with ancient epidemics.”
For the evolutionary biologist, these ancient epidemics did not turn out good: there were many deaths and suffering.
. Throughout the history of evolution, humans have been hit by hundreds of epidemics.
“The populations that existed did not have any medicine or vaccines like the ones we have now,” he reflects.
“The impact of vaccines in improving our lives has been impressive.”
What Enard’s branch of study has deciphered is that our ancestors “were very quick to adapt to the threat of viruses and pathogens ”.
It became a necessity: adapt to survive.
Any adaptation process that happened in the past, he explains, was probably due to a virus that emerged at the time “and perhaps did not offer any benefit against a virus in the present.”
However, what seems clear is that among the various factors (changes in the environment, in the climate, in the diet) that have led us, as a species, to have adaptation processes, viruses and pathogens have a place starring.
“A huge proportion of the adaptation that can be detected in human genomes may be connected to ancient pathogens“He clarifies.
From generation to generation
But what does it mean that adaptation processes have taken place in our genomes?
. According to Enard, many genetic mutations have no effect on people who have them, but others can cause disease.
“In our genome there are mutations,” he explains. “For example, children have new mutations when compared to their parents.”
These are small pieces of DNA that mutate because the parents’ DNA was not faithfully copied at the time of reproduction, the scientist points out.
“Those mutations often do not cause anything, other times they cause disease, but other times, in the context of an epidemic, small parts of these mutations in some people can be beneficial because they can recognize the virus (which they once knew ) and face the infection ”, says the professor.
“Think that these people with new mutations are more likely to survive and have children than those without the mutations.”
This is how generation after generation, the frequency of these mutations increases rapidly.
“You can see adaptive mutations that provide better survival mechanisms in response to viruses ranging from 1% frequency to 60% frequency ”, indicates the researcher.
That increases the chance of surviving the viral infection.
And that process is something that can be detected in people’s genomes.
They haven’t made us stronger
Enard clarifies that the pandemics and adaptation episodes that they have caused in humans throughout history have not made us stronger.
“If so, we would not become infected as it is happening now.”
.Illustrations showing corpses on the streets of Hong Kong amid the bubonic plague.
“The adaptation process our ancestors went through to survive ancient viruses are not effective against new viruses because they are different”.
The new enemy, reflects the biologist, looks different. Therefore, a genetic strategy must be designed by our body.
What makes us stronger is not only that we have medicines and vaccines, but with scientific investigation.
“From passively suffering and dying without knowing what is happening, as it happened in the past, now we know what is happening and we can do something.”
Many of the adaptation processes against viruses have occurred in genes linked to the immune system because they are the ones that specialize in attacking pathogens.
.Genetics and socioeconomic factors are two of the elements that make some people more likely to develop certain diseases.
However, the specialist points out, adaptation can also occur in other genes that do not have to do with the immune response.
“Any gene, in charge of any function, that is hijacked by a virus for replication, can also be adapted to avoid being used.”
So are people who don’t develop a disease because they have mutations that help them? I asked him.
“No, what we are seeing right now with people developing (or not) COVID-19 is that there are socioeconomic factors involved.”
“It is very likely that what our research is going to find is that socioeconomic factors, in these special circumstances, are playing an even more important role than genetics.”
“Genetics may have a role but to a lesser extent when compared to socioeconomic factorsFor example: how densely populated is the place where you live, how healthy you are considering your income. ”
So could this pandemic we are facing from SARS Cov-2 be explained by looking at our past?
.In London, workers washed the streets during the cholera pandemic of the 1890s.
“It can be explained, but not necessarily if we study particular human genomes or if we analyze human evolution, but if we investigate why viruses infect other species, for example, bats and other mammals,” he explains.
“From an evolutionary perspective” -says the scientist- “what we can see is if there were ancient viruses related to the current coronavirus, which have potentially infected human populations in the past and if it happened, see how strong it could have been adaptation to those viruses. “
In the face of the current pandemic, Enard believes that people cannot feel totally powerless over what is happening.
“Scientists can use the genomes to learn about ancient epidemics and what harmed ancestral populations.”
And with that as a starting point, you can better predict which viruses and pathogens are most likely to cause devastating effects on the population.
“Statistically, what was a problem in the past, is very likely to be a problem in the future,” he reflects.
Looking for the one with the green eyes
Enard’s studies are pioneering, as this is a new field of research.
.As if it were a family tree, Enard and his team look for mutations that arose in adaptive processes against ancient viruses.
“We use powerful computers and with the genomes of people we rebuild genealogies. We have these giant family trees of relationships between different people and by knowing those links for very long periods of time, we can see where and when mutations occurred adaptive ”.
For example, he tells me, if we develop a family tree in which the members of it have green eyes, we can determine which of the ancestors was the first with green eyes and perhaps that color occurred due to a mutation in that particular ancestor.
In this way the characteristic of green eyes was transmitted to the descendants.
“We do the same with mutations that arose from adaptive processes against specific viruses. We can see when an ancestor had the mutation for the first time, “he says.
Enard considers it too premature to determine the mutations of this coronavirus.
.Enard explains that mutating viruses are like an enemy that constantly changes its appearance.
And he insists: “That is an example that past adaptations have not made us stronger. That is the case of a virus that changes and becomes a new enemy all the time”
“In the case of coronaviruses, we don’t know if it will mutate much. More research is needed. “
What the scientist does rule out is that SARS Cov-2 can generate mutations in our genes.
Although there are viruses that can do this (such as HIV) and are known as retroviruses because they can make copies of themselves that integrate into the genome of the host, the coronavirus is not of that type.
Enard believes the war on viruses is not being won.
“One of the reasons to be concerned is that because there is now more contact between large human populations and wildlife“Statistically, there are going to be more possibilities for transmission of viruses from an animal species to humans compared to what happened in the past.”
“I am hopeful that this new epidemic will be a wake-up call to be more careful and more alert in monitoring viruses and the threats they represent,” he reflects.
“And of the importance of do not disturb to fauna as it has been done in the past ”.