While viruses have long been cast as the ‘villains’ of the biological world, the real story reveals a surprising twist. Unveil the hidden power of evolution and survival – viruses. Their pivotal role has shaped life on Earth and will continue to aid in the survival of living organisms, including humans.
Author: Emily Yang
Artist: Emily Yang
Editor: Rachel Nguyen
‘Virolution’ means virus driven evolution, a term coined by the author Frank Ryan in his book ‘Virolution: The most important evolutionary book since Dawkins’ Selfish Gene’. The theory presents a virus-centered view of life, suggesting that viruses are not solely agents of disease, but have always been key drivers of evolutionary change, much like other well-known mechanisms such as natural selection and genetic mutation. It has been found that viruses have a fundamental role in the development of life forms as well as the survival of the human race. Virolution involves the concept of a ‘virolutionary arms race’ in which viruses and hosts influence one another’s evolution, necessitating continual adaptation. This has led to the evolution of various defence mechanisms in living organisms.
Viral elements constitute over 43% of the human genome, far exceeding the 1.5% attributed to the vertebrate component – the very essence of what makes us human. Viruses have significantly reconstructed the human genome by repeatedly integrating their genes into our DNA via symbiogenesis. This process starts with the virus colonising the human genome via infection from a closely related species, such as with the example of the simian version of the HIV that came from chimpanzees and mangabey monkeys. What follows is aggressive symbiosis, during which viruses challenge human survival through the course of epidermis and pandemics, ultimately leading to a profound transformation of the human genome.
The best explanation of aggressive symbiosis comes from the example of the relationship between virus and bacteria. Inside a bacterium, a virus deposits a copy of its genome that codes for two products: a long-lasting toxin and a short-lived antidote that protects the bacterium from the toxin’s effects. From the bacterium’s perspective, it appears advantageous to rid itself of the virus. However, when the bacterium attempts to eliminate viral entities, the anti-toxin effects wear off, while the persistent toxin continues to operate. Paradoxically, this viral strategy kills all bacteria that do not possess the virus themselves.
This initial appearance of aggression and selfishness ultimately transforms into a mutualistic relationship. Bacteria containing the protective virus become resistant to infections by other related viruses, including endogenous retroviruses. The newfound partnership sets the stage for the host’s population to re-expands while co-evolving alongside the virus. The consequence is a reproductive separation between bacteria with the virus and those without. This process highlights the pivotal role of viruses in propelling the forces of evolution.
Aggressive symbiosis can give rise to a different phenomenon known as ‘plague culling’. In this phase, viruses serve as covert allies to their hosts, infiltrating and attacking organisms lacking the protective viral shield. A notable example is the conflict between indigenous British red squirrels and imported grey squirrels from America. Grey squirrels carry squirrel pox virus, which, although harmless to them, proves fatal to the red squirrels. Here, the virus strategically aids the grey squirrels by eradicating their competitor.
The colonisation of the human genome has yielded profound benefits for our survival, becoming an evolutionary driving force. Viral genes play crucial roles in regulating the production of keratin, hormones, enzymes and even contribute to the development of essential structures like the placenta and immune system. These viral components are also expressed in various vital organs, including adrenals, testes and the brain. However, the improper sequencing of these viral genes by human’s transcriptional machinery can also lead to disorders such as multiple sclerosis, haemophilia and cancer, which shows how important the role of viruses has played in our development. The colonisation of the human genome by viruses is an ongoing process and as time progresses, the viral proportion of our genome is expected to increase, ensuring that viruses continue to shape and influence the evolution of the human species.
Virolution is a truly groundbreaking concept that presents a compelling argument for the central role that viruses have played in the evolutionary history of life. Further research is required for a deeper understanding of the virolutionary processes which can have implications for medicine, genetics, and evolutionary biology, and lead to new insights into disease prevention and treatment.
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