This article delves into genealogy from a unique perspective, focusing on the origins of viruses—a topic modern scientists approach through three primary theories.1 These perspectives are examined in detail below.
1. The Coevolution Theory
The prevailing theory suggests that viruses, akin to other biological entities, emerged by evolving progressively towards the formation of the earliest cellular structures. The modern interpretation of this hypothesis, termed the coevolution theory, rejects the view of viruses as “semi-cells” or as precursors to fully developed cells.
Instead, this theory proposes that viruses should be regarded as conglomerates of nucleic acids and proteins, capable of exploiting the metabolism of host cells to sustain their presence. In essence, they replicate and adapt within the intracellular environment, thereby coevolving alongside their cellular hosts.
2. The Regressive Theory
The second theory, referred to as the regressive theory, proposes that viruses are viewed as vestiges of once-living cells that transitioned to a parasitic existence, progressively shedding all components nonessential to survival within a cellular environment.
These two theories for the origin of viruses have long been established, yet they have largely exhausted their capacity to address the fundamental question of viral origins. Today, these explanations persist not as definitive theories but as interpretative perspectives, acknowledging the inherent challenge in scientifically substantiating such views.
How can we evaluate the evolution of viruses when the trajectory of changes in viral particles remains unknown and unverifiable? In other words, it is unclear whether viruses are evolving or regressing. That is, unless we adopt an ideological stance—assuming evolution occurred, regardless of the specifics, with the primary concern being the occurrence of some form of evolutionary change.
3. The Escape Theory
A more recent explanation for the existence of viruses is the “escape theory,” which has sparked some hope, particularly due to its potential for empirical verification, or at least for confirmation and/or falsification.
According to the third theory, viruses did not arise as distinct, autonomous entities within evolutionary history. Rather, they represent fragments of genetic material that were already extant with the advent of cellular life. Under this theory, a virus may be conceptualised as a segment of DNA or RNA that has exited one cell and subsequently integrated into another. In this framework, any “transferrable” fragment of nucleic acid, secondarily encased within proteins—some enzymatic, others structural—and possibly enveloped within a lipid membrane acquired during passage through a cellular boundary, is recognised as a virus, manifesting as either a virion or a nucleocapsid.
In view of this theory, transposons and plasmids may indeed evolve into viruses. It is worth recalling that “naked” nucleic acid is referred to as a viroid, whereas a virus exists either as a virion or a nucleocapsid. An intriguing question arises regarding the potential mechanisms by which a virus might develop from a viroid under present Earth conditions—a process that appears quite feasible. The implication of this, from both a philosophical and practical standpoint, is that the origin of viruses, and possibly their sole origin, lies within living cells.
The Cellular Origin of Viruses?
In line with this theory, viruses are understood as a secondary development following the advent of life on Earth, arising as by-products of cellular processes. Some proponents even suggest that viral creation is a natural mechanism through which cells dispose of defective or otherwise compromised elements of their genetic apparatus.
The issue remains complex. From the perspective of current scientific understanding and the prevailing paradigm within the natural sciences, it appears intractable, at least for the foreseeable future. A viewpoint is gradually emerging that multicellular organisms may result from a form of “cooperation” among viruses, suggesting that living cells could have arisen through the “aggregation” of viral entities—though such a view may seem difficult to take seriously. However, it is precisely this speculative nature that warrants attention, as many ideas once dismissed as absurd or ungrounded, such as phrenology or eugenics, have historically evolved into fully-fledged theories and gained traction among proponents.
This perspective arises from the observation that, based on analyses of viral and human nucleic acid sequences, approximately 30% of the human genome is attributable to various viruses. Some of these sequences are regarded as “fossil viruses,” referring to viruses that integrated into the human genome millions of years ago. Notably, it has been demonstrated that at least one virus, HHV-6, can integrate into human DNA even today. This collection of DNA sequences2, thought to have a viral origin, is collectively termed the virome3.
However, this observation may be more plausibly explained by a reverse mechanism, namely the “shedding” or “elimination” of RNA segments and mobile DNA fragments by the cell into its environment. An important question thus arises: under what conditions, and through which mechanisms, might such a process take place?
We may eventually address this question, though it is unlikely to feature prominently in primary articles intended to introduce the world of viruses, both as biological phenomena and from practical perspectives. Such primary discussions will likely focus on applying this knowledge to medical contexts—whether in diagnosing disease processes or developing preventative strategies.
Read the second part of the article, which delves into the origins of viruses.
About the Author:
Dr Dariusz Struski is a medical doctor and specialist in family medicine, with thirty-two years of experience across Poland, Sweden, and Norway. He is the former head of the Family Physicians Training Centre in Wrocław and currently serves as a lecturer in Evidence-Based Medicine and family medicine, with a particular focus on infectious diseases.
By the way, we recommend reading the articles:
- Interactions Between Viruses and Human Organisms
- Defining the Human-Animal Divide
- Exploring the Origins of Religion
- Unicorns in the Bible – Myth or Reality?
- Human Races: A Scientific Perspective
- What is the Higgs Boson?
Footnotes:
- Goździcka-Józefiak, A. (ed.) (2019) Wirusologia. 1st ed. Warszawa: Wydawnictwo Naukowe PWN.
- Prescott, L.M. (2002) Microbiology. 5th ed. New York: The McGraw-Hill Companies.
- Mandell, G.L., Bennett, J.E., and Dolin, R. (2015) Principles and Practice of Infectious Diseases. 8th ed.
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