History of Viruses: How Did They Originate?
Introduction
Viruses are the most primitive form of parasites that remain in an inanimate stage when they are outside the host body. They do not have the capability of continuing the life processes on their own as they depend on the enzymes and other biochemical substances present in a host. In simpler words, viruses are something between living and nonliving things. Fascinating, isn’t it?
Well, how did they originate in the first place? Where did viruses come from? It is very hard for scientists to zero in on such concepts. There are theories but we do not have solid proof. Let us find out what these things are in detail and then proceed to find out the theories of their origin.
What is a Virus?
Viruses are obligate parasites which are made of proteins covering a nuclear material (either RNA or DNA). They are generally infectious to a particular species. This species acts as the host for carrying on their various biological processes. These biological processes are not possible to be conducted in absence of a host body. If you see a viruses diagram, you will understand how simple these microbes can be.
This simple form of microbes can be very devastating. We have multiple examples that prove the morbidity of virus infections. For instance, smallpox, one of the deadliest diseases the medical world got rid of, is a stubborn virus that infected and killed a lot of people. With proper vaccination and medical care, we have been successful to eradicate this disease from the world.
Unlike other life forms, viruses cannot grow or multiply on their own. Their sole purpose is to infect a host, use the biochemical substances inside them, multiply and spread to infect other hosts. Some organisms even serve as vectors to carry particular viruses. Now that we have a simple idea about viruses, let us find out more about the hypotheses of their origin.
What are Viruses?
The Progressive Hypotheses
As per this hypothesis, viruses originated from simple genetic material. We have discussed earlier that these microbes have a simple yet effective protein covering over a small amount of genetic material. There are no cell organelles present in viruses. Hence, we cannot consider viruses as cells.
According to this theory, they act as a special piece of genetic information that knows how to penetrate and infect a host and multiply to infect more. Another thought of this hypothesis is that scientists think that viruses may have been generated from our genetic materials. The special genes called transposons present in our system match that of the viruses.
These transposons are also known as jumping genes. They have the unique capability of jumping from one location to the other. It means that these genes can literally change the definition of genetic information an animal has and can develop a new microbe from scratch.
From this hypothesis, we can consider viruses as packets of jumping genes that replicate and form new viruses in a host body. This can be the history of viruses and considered their origin. They also leave the cells after infecting and duplicating to infect other cells. This is why their features match that of the transposons.
The Regressive Hypothesis
As the name suggests, this is exactly the opposite of the hypothesis we just discussed. This theory suggests that viruses are the reduced form of parasites. It means they have been reduced to a primitive form of microbes displaying parasitic features.
This can be a believable explanation of the origin of viruses. Consider this example of virus. Mimivirus is the largest virus we know. Its size is 50 times less than the thickness of our hair strands. Despite this micro figure, it is a monster of viruses. It means the other viruses are much smaller in size.
This has made scientists think that smaller viruses of different kinds might be the result of the breakdown of such big viruses. This hypothesis does not answer the question of the origin of the virus clearly though. Where did the large viruses come from?
According to this theory, they have evolved smaller from their large ancestral forms, the first virus in the world. The ancestors were complex microbes with bigger genetic impressions. It is believed that these viruses were symbiotic to other animals. Eventually, they turned out to be smaller and parasitic in nature. The process of evolution and adaptation might have made them more sustainable in the parasitic form.
Virus First Hypothesis
This hypothesis has an entirely different theory to present. Studying the different types of viruses biology, scientists have inferred that viruses are the first hint of life in prehistoric earth. This hypothesis suggests that viruses existed before cells. This topic is quite debatable but cannot be ruled out totally.
Evidence suggests that viruses are the most primitive form of protein and genetic material that can replicate. It can be the beginning of life form on our planet. Scientists argue that viruses in the world existed way before life has taken a complex form. We observe carefully, we will surely find out that viruses are much simpler than even the simplest cells.
No Correct Explanation of Virus Origin
We can clearly understand that all these hypotheses are debatable. Their origin has always been a question since its discovery. For your information, Dmitri Ivanowsky was one who invented viruses in 1892.
Since then, we have a vivid RNA and DNA viruses list. We can easily identify viruses by analysing their genetic material and protein structure. We have ways to tackle the infectious diseases caused by these tiny microbes but have no way to find their origin. The lack of solid scientific proof does not let us make a conclusion.
