I observed something curious when I went to the blood bank two weeks ago. While I was lying on the bed and my blood was gradually filling up a plastic pouch next to me, a staff member hurriedly switched on the TV.
Wondering why the urgency, I turned around to see the nation’s most recognisable doctor’s daily briefing blaring to life. For the entire duration of Dr Noor Hisham Abdullah’s speech, everyone’s eyes were glued to the TV.
Noor Hisham’s daily address has become a national obsession now – it’s watched with rapt attention and later becomes fodder for conversation. As I observed this, I couldn’t help but wonder how the Covid-19 virus – a tiny packet of protein that’s so small that it’s even difficult to observe via a microscope – came to dominate the globe and our collective consciousness.
An unseeable enemy that is feared by all – one that has strained relationships, forced people to stay apart, and elevated worldwide depression and anxiety levels to never-before-seen highs.
But as unique as SARS-coV-2 is, it’s not an entirely novel entity. It’s still part of the virus family – a family that has caused much pain and anguish to our human family over millennia. But is it only that? Science is revealing that viruses are far more complex and interesting than we previously thought.
For starters, viruses are notoriously difficult to compartmentalise, defying the human need to put everything into boxes. Are they even alive? To find out, we need to examine the criteria that makes something a living thing:
| Criteria for life | Description | Do viruses satisfy the criteria for life? |
| Able to reproduce | Reproduction is the ability to duplicate DNA and pass it on to offsprings. A single virus particle (a virion) can reproduce but they don’t have the machinery necessary, i.e. the ribosomes, nuclei, and organelles to do it. So in order to reproduce, they need to hijack the cellular factory of a living organism and use its tools to reproduce and multiply. | Partly |
| Able to grow | Both unicellular and multicellular organisms gradually become more complex and larger over time. Viruses, on the other hand, are created exactly as they are and never grow. They only increase in numbers, never in size. | No |
| Able to maintain internal conditions (homeostasis) | Living organisms meticulously keep their internal conditions such as pH, temperature, and chemicals regulated and balanced. Viruses do not have the machinery required to monitor and keep their internal environment consistent. Though some say that its capsid – its protective protein shell – keeps it insulated and protected from environmental changes, it isn’t dynamic enough to be considered to be maintaining homeostasis. | No |
| Able to use energy | Viruses use energy to make copies of themselves, but they don’t use their own energy or machinery. Instead, they hijack and use those of the host organism. | Partly |
| Able to respond to stimuli | A feedback loop is essential to be considered life. For instance, plants bend towards a source of light and bacteria move towards or away from chemicals. Viruses haven’t yet been observed to exhibit such behaviour. | No |
| Possess a complex level of organisation | Living organisms have multiple levels of organisation of incredible complexity. A nucleus, ribosome, mitochondria, cytoplasm, and many more things combine to form an animal cell. A combination of cells form a tissue, which in turn form an organ which in combination with other organs form organ systems which ultimately form an organism. However, a virus like SARS-coV 2 has RNA enclosed in protein, spike protein, and a lipid membrane, among other things. It’s simpler but it certainly still has a high level of organisation. | Yes |
| Able to adapt to their environment | Viruses switch between actively replicating themselves and incorporating their DNA into the host cell’s DNA so they replicate when the host replicates, staying relatively dormant – the lytic and lysogenic phases, respectively – depending on which can be supported by the host’s conditions. They also make many copying mistakes that result in mutation over time. This is what leads to drug or vaccine-resistant virus strains. | Yes |
So we can see that viruses only clearly exhibit two of the seven preconditions for being considered alive.
So, viruses aren’t alive in the sense that you and I or even bacteria are alive. But at the same time, they are not unalive like a rock or water are. They straddle the line between being life and non-life. So in a way, they are the closest entities the real-world has to zombies.
Viruses, put plainly, are the living dead.
Or as my close friend, Lee Rajkhowa, quite pithily pronounced, “Viruses are the undead trying to make us dead”.
But they’re not all villainy – at least not entirely. Recent studies have suggested that humans and viruses may share a long, intertwined history. To explore it, we need to find out how viruses originated – which three main hypotheses attempt to explain:
1. The Progressive Hypothesis: Viruses evolved from strands of DNA or RNA that devised a structural, coat protein and exited the cell in which they were made. This allowed it to move freely from cell to cell, infecting them and multiplying itself. This hypothesis was derived from the fact that viral-like retrotransposons that are part of most eukaryotic cells and retroviruses share striking similarities.
2. The Regressive Hypothesis: Viruses were previously fully-functioning cells that atrophied and lost all other functions and machinery except for their genes and coat protein. This led to a gradual process of parasitism and eventually its need to hijack a host to replicate. This hypothesis was derived from studying the giant Mimivirus that was found to resemble a type of parasitic bacteria.
3. The Virus-First Hypothesis: A more recently posited hypothesis – which turns the previous two hypotheses on their head – suggests that all life evolved from viruses. Its proponents say that viruses first emerged in a precellular world, some of them gradually becoming more complex and forming cells – the building blocks for all life today.
Of course, there’s the possibility that none of these hypotheses hold all the answers but rather form pieces of a larger puzzle. Some or all of them could be true, giving birth to different viruses in different ways, explaining their deep diversity that we see today.
Dr Luis P Villarreal, a virologist at the University of California, Irvine, thinks that irrespective of their origin, our DNAs might be carrying the fingerprints of ancient viruses. He says: “The huge population of viruses, combined with their rapid rates of replication and mutation, makes them the world’s leading source of genetic innovation: they constantly ‘invent’ new genes. And unique genes of viral origin may travel, finding their way into other organisms and contributing to evolutionary change”.
He goes a step further by saying that we might have inherited our all-important cellular nucleus from viruses. He contends that the evolution from prokaryotic cells (a nucleus-less organism, such as a bacteria) to eukaryotic cells (a cell with a nucleus, which makes up all animal and plant life) can’t satisfactorily be explained by gradual evolution.
Instead, around 1.6 to 2.1 billion years ago, a large DNA virus might have made its way into a prokaryote, spurring its evolution into a eukaryote, which ultimately gave birth to all the major forms of life we see around us today, including you and me.
This means that the eventual advent of humans might have only been made possible by DNA that we inherited from ancient viruses. Without them, we might not even exist in our current form.
So in a loose sense, we may all be viruses expressing ourselves as humans.
Now, how’s that for a mind-bender?
The views expressed are those of the author and do not necessarily reflect those of FMT.
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