Astro-pathogens, exo-infections and xeno-medicine (plus a physician’s approach to panspermia)

Maybe a pathogen from outer space will wipe out all intelligent life on Earth. Perhaps it already has. In any case, what sort of virus might it be? Adenovirus (I-don’t-know-virus).

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Learning objectives

1. Explore the current thinking behind pathogen viability outside Earth

2. Consider the panspermia hypothesis and potential relationship to pandemics

3. Reflect on how physicians reconcile science with sensationalisationion

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I realise that from the perspective of the average human physician, the discussion of extra-terrestrial pathogens is super-niche. Indeed, after reading this post, you may feel like the detailed understanding of the commonly but undeservedly derided Kreb’s Cycle to everyday clinical decision making is going to be relatively indispensable.

Yet, I feel that examining such esoteric issues from the perspective of a health care worker can assert the importance of understanding the fundamental principles of clinical science. This ability to think and challenge ideas (even if they are obscure) does have a relevance on patient care. For example, a clinician may wish to debunk emerging conspiracy theories to improve vaccination rates or question longstanding medical myths.

The power of effectively communicating scientific ideas with our patients in a manner that also challenges ill-informed rhetoric should not be dismissed. Adding, for example, cultural reference points to our conversations with colleagues and patients allows important information to permeate into the relevance of everyday real life. It also reduces an increasingly portrayed disconnect between experts and those who are not. Whether or not such an approach will be effective in improving clinical outcomes is, however, another issue.

Regrettably, in the current climate it still feels necessary for me to make it clear as dilithium that I personally don’t believe that pathogens from outer space are responsible for human disease. I do however feel that the scientific pursuit of learning more about ourselves and the universe is important and fascinating. Of course, I encourage you to come to your own conclusions but let’s be honest, this blog post is really yet another thinly veiled excuse for me to talk about medicine and science-fiction again.

Before we delve into the issue of alien microbes, first a word on the importance of words. As all physicians know, medicine has its own hybrid language; the nomenclature of hypothetical extra-terrestrial pathogens being unnecessarily convoluted perhaps then comes as no surprise.

Astro originates from the Greek word astron (star). Exo originates from the Greek word exo (outside). Xeno originates from the Greek word xenos (stranger). Astrobiology, exobiology and xenobiology are often used synonymously and although they may overlap, there are important differences. Many of the definitions I found were ambiguous, fluctuant depending on the time when they were used and sometimes contradictory, but here’s my interpretation:

Astrobiology – a broad term that is multidisciplinary concerned with the study of the origin, evolution and distribution of life in the universe including that of the future of life on Earth and beyond.

Exobiology – deals with the possibility and likely nature of life beyond Earth including the survivability or adaptability of Earth organisms under non-Earth conditions (can sometimes fall under the umbrella term of astrobiology or be synonymous with it).

Xenobiology – concerned with biology of life forms with non-standard biochemistry sometimes including the speculative biology of extraterrestrial life forms (can overlap or fall within the field of synthetic biology that aims to design and construct new and unnatural biological systems).

The taxonomy of organisms is already a complex business. The terms astropathogen, exopathogen and xenopathogen (that at the time of writing have no significant presence in medical terminology) will have different connotations. To be clear, I’m no expert in these fields, I’m approaching the subject from the perspective of a modern day physician.

In an instance of nomina perplexa, there will be the obvious confusion between astroviruses and astropathogens, nomen ambiguum between an exopathogen being an organism that is external to the human body versus one that is external to Earth as well as nomina periculosa if xenopathogen perhaps being used to refer to animal (non-human) origin (e.g. xenograft). To add to this disorientation, there could be further bewilderment for some when initially trying to distinguish between the medicine of astrobiology and the influence of astrology on medicine sometimes coined astromedicine. I’ve probably alienated most readers by now, so if you’ve got this far, well done for putting up with me. After all, I’m a doctor Jim, not a taxonomist.

Once we have gotten over the very human problem of naming things, we must consider whether there is (or ever will be) any organism to actually name from outer space. The sheer hostility of the cosmos is perhaps one of the major obstacles preventing many of us to even conceive of such a thing. So let us return back to Earth for a moment to consider instances where organisms have surprised physicians with their resilience.

Helicobacter pylori (and just to drill in the point about taxonomy, it was previously called Campylobacter pylori) is a prime example of an organism that has defied conventional medical doctrine. Active H. pylori infection being shown to cause inflammation in the hostile acidic environment of the stomach famously led to a Nobel prize for Marshall and Warren. However, the jump from an organism being able to survive within the human antrum to the chamber of cosmic space is one that no normal flagellum could make.

Even so, the concept of an organism being resilient enough to manage the conditions of space is perhaps not as fictional as it sounds. Indeed, humans have potentially seeded the ultra hardy Tardigrades (thought to be able to survive the vacuum and radiation of space) on the moon. Focusing on bacteria, Deinococcus has proven highly resilient to environmental hazards (including radiation) and have been found to survive outside the International Space Station.

So conceptually, the prospect of a microorganism existing outside of it’s usual Earth habitat has been demonstrated, albeit unintentionally. I wonder what might be present on Voyager 1 and whether billions of years from now we will be inadvertently responsible for colonising a distant fertile planet for the annihilation of an alien civilisation. In an alternate universe, perhaps we decide to enclose a packet of ciprofloxacin on all deep space missions to help treat our alien friends or indeed highlight our own microbial vulnerabilities. Yet one more reason why microbial stewardship is so important.

I just mentioned the potential for colonising a distant planet with a hardy or protected microorganism. Indeed, the idea of life on Earth actually originating from outside of our own planetary sphere has been knocking around for sometime. The panspermia hypothesis proposes that life has been distributed throughout the universe by meteoroids, asteroids, comets and so forth that are carrying microorganisms. As you can imagine, the hypothesis is quite polarising but is gaining increasing attention.

In 1996, A NASA research team suggested that life may have existed on Mars a few billion years ago. This was based on finding what some people interpreted as possible microbial fossils on a meteorite called Allan Hills 84001. Of note, Bill Clinton remarked on the findings in a memorable press conference. This had an important effect both in public perception of the issue and the subsequent funding that space exploration organisations received.

There have been a number of refutational arguments including those regarding possible contamination, that the reported fossils appear very small in comparison to known bacteria or historically hypothesised organisms, plus the additional point that morphological appearance alone should not be used to confirm the presence of primitive life.

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Questions

When might appearances be deceptive in clinical medicine?

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As most physicians are aware, appearances can be highly subjective and interpreted in different ways. Consider how we may incorrectly report or miss that a patient may be anaemic or jaundiced for example.

But if life is more ubiquitous in the universe than many might think, further voyages into the cosmos, especially with space tourism, could bring humans and extraterrestrials into contact. This could happen in a few different ways.

One hypothetical scenario is if humans or thier spacecraft are exposed to a novel microorganism in space. The extraterrestrial organism may simply be floating around and come into contact with the vessel or the astronaut suit. Infection, for example when taking off spacesuit or when the spacecraft returns to Earth would expose all planetary life to this new potential pathogen. This worry about back contamination is one of the reasons the crew of Apollo 11 were quarantined when they arrived back on Earth:

“…scientists became more concerned about the potential for back contamination. Since no one had ever been to the Moon, it was impossible to be absolutely sure that there were no biological threats to life on Earth… Many space experts argued that conditions on the Moon made it impossible for any life form to survive, but these agencies felt that even the smallest risk of back contamination must be prevented. As a result, a quarantine program was incorporated into the LRL (Lunar Receiving Lab), significantly complicating the original plans for the laboratory. In time, the people concerned about the potential for lunar organisms, through the Interagency Committee on Back Contamination (ICBC), came to have the strongest voice in the LRL’s design and how it functioned.” 

Lunar Receiving Laboratory Project History, 2004

Today, there are similar precautions with a Mars Sample Return Receiving Facility in the pipeline. These measures are mandatory: The Committee on Space Research’s (COSPAR) Planetary Protection Guidelines stipulate that “the Earth must be protected from the potential hazard posed by extraterrestrial matter carried by a spacecraft returning from an interplanetary mission.” and The Outer Space Treaty also outlines the concerns regarding both forward and back-contamination.

Another possibility is that terrestrial microorganisms hitchhiking on astronauts and/or vehicles may mutate and evolve in a new environment due to new selective pressures. Indeed, astronauts are full of their natural bacteria and their spacecraft will have all sorts of things attached to them. Adding a little momentum to this idea, new species of the Methylobacteriaceae family have been identified on the International Space Station. We could postulate ideas around radiation causing structural changes, mutations and altered cellular metabolism but more likely, they simply hadn’t been identified amongst the innumerable unidentified microorganisms present on Earth before they launched into space.

However, there a a number of pathogens from Earth that have been found on our spacecraft and indeed some have been found to have increased virulence once exposed to the environment of space. This seems particularly concerning since the immunity of spacefarers appears to be disturbed under the influence of microgravity, space radiation and stress. Imapired immune function combined with space radiation is concerning when considering risk of malignancy. On a more benign note, latent zoster reactivation, for example, seems to be a significant concern even in super-healthy astronauts let alone the the pending influx of super-wealthy space tourists in the future.

Anyway, any new microbial variant may subsequently infect its human chauffeur(s) (therefore creating the terrifying prospect of the new branch of medicine that would be exo-immunology) either in space or any potentially any other lifeform if they are taken back to Earth and let loose in another example of back contamination.

Alternatively, a vector from space (e.g. a meteorite) contaminated with a resilient microorganism may simply land on our planet. More than 100 tons of material from space hits Earth every day, although most of this will burn up in the atmosphere. Potentially surviving the friction and heat of re-entry, any life-form may or may not be pathogenic to species on Earth.

A number of organisms have now been tested in the conditions of space with a particular emphasis on whether survival is possible within rocks (i.e. simulated meteorites) to test the idea of lithopanspermia. If we consider the hypothetical situation that an extraterrestrial microorganism could somehow be introduced to the Earth environment, how would it behave? It’s probably useful to consider native Earth history and scenarios first.

One important historical example is the European introduction of endemic Old World diseases such as smallpox, measles and chickenpox (plus many more) to the previously unexposed New World that decimated the population of the Indigenous peoples of the Americas. Reports on case fatality in the New World are uncertain but were very high, varying perhaps from 50%-95% of the population. Additional factors may have contributed to this vulnerability including social disruption where so many of the population were simultaneously sick, there were few, if anyone, left to care or provide for the ill. A significant proportion of the population were immunologically naive to the pathogens, yet the pathogens were already adapted to interact with humans. This imbalance was catastrophic.

The reverse process could also occur and there is still debate over whether syphilis was part of this Columbian Exchange. In science fiction, we have the classic example of the Martians in H.G. Wells The War of the Worlds succumbing to the natural pathogenic microbiome of Earth. Indeed, the anxieties over imperialism may have led Wells to develop the story, contemplating the sudden arrival of the British in Tasmania. The idea of invasivity or the harmful rapid spread of an organism is not limited to pathogenic microorganisms. Earth examples include Japanese knotweed, the grey squirrel or even the Escobar Hippo. Some may even consider humans themselves to be the paragon invasive species on Earth.

From the moment the invaders arrived, breathed our air, ate and drank, they were doomed. They were undone, destroyed, after all of man’s weapons and devices had failed, by the tiniest creatures that God in his wisdom put upon this earth. By the toll of a billion deaths, man had earned his immunity, his right to survive among this planet’s infinite organisms.

War of the Worlds, the 2005 movie adaptation

But humans are exceptionally modern creatures when we consider the history of the Earth (let alone the universe). Earth is, and has been, home to many different forms of life that are now extinct. However, it is possible that some organisms, including pathogenic microorganisms may lay dormant in areas such as the frozen permafrost. It has been considered that climate change may melt the ice allowing humans and ancient Earth pathogens to come into contact for the first time.

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Questions

Should physicians have a clear role in caring for the environment and ecosystem that support our patients?

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Whether or not our modern iteration of an immune system would be able to combat such a defrosted organism is obviously unknown. Importantly, such a pathogen would have evolved upon Earth and perhaps shares some of the basic biochemical structures we associate with life. This home advantage is one of the concepts I consider critical when considering the nature of human and pathogen interaction. The lack of a shared planetary heritage would likely be a major obstacle for a non-Earth pathogen causing disease in humans, or indeed any Earth species.

Staying with the colder areas of Earth, let’s explore a specific example of how host physiology would be important while also reminding ourselves of one of the best science fiction alien pathogen movies of all time, John Carpenter’s The Thing. Even though the tagline is that man is the warmest place to hide, humans have a normal body temperature around 37C whereas dogs (which also feature in the movie) have a normal temperature of about 38.5C. The assimilating alien organism in The Thing may have therefore preferred remaining in the dog rather than attack the humans in various Antarctic research stations. But pedantic plot holes aside, this revelation raises some points to reflect on.

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Questions

Why would any alien organism behave in a manner that a human would rationally expect?

What are the chances of an alien organism being able to manipulate human physiology?

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Thermoregulation is critical for optimum physiology and plays an adaptive role in the response to infectious agents. Pyrexia seems to be an important response in altering the host-pathogen interaction, indeed why would fever which is such a costly process evolve without an important advantage? Specific temperature changes can modify gene expression and molecular conformation both in the host and pathogen. It is an exquisitely complex and evolutionary rich dance between offense and defence.

In The Thing, the alien organism does indeed have a heat threshold when the researchers try to establish who is infected, yet it is also able to somehow persist exposed in the cold of the Antarctic. It can jump between species, mimic them and continue to function well. It suggests that such an organism may be bereft of the basic molecules or features we consider to be essential to Earth-based life thereby questioning whether we could consider it a life-form at all. Even with panspermia (which would suppose a common ancestor), an organism outside of an Earth environment may have evolved and/or changed to a state that is simply unrecognisable to what we consider to be ‘alive’.

“…it is likely that alien microorganisms are adapted to entirely different conditions than those in terrestrial environments, are much less well adapted to the conditions of the human body, and will likely be less capable of colonization or invasion than our own microbiota.”

Immune recognition of putative alien microbial structures: Host–pathogen interactions in the age of space travel (2020)

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Questions

On what basis could such an organism (even if we could call it that) interact with Earth organisms?

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There have already been some notable challenges in the definition of life, such as prions (or proteinaceous infectious particles) that in contrast to all other infective agents contain no nucleic acid genome. Prions are transmittable misfolded proteins that can induce nearby benign and healthy proteins to themselves refold into the pathogenic abnormal conformational shape. A type of ‘copy and paste’ if you will. The prion itself is very resistant, evading common methods used to sterilise medical equipment including chemical disinfection with alcohol and thermal treatment including boiling and UV light exposure. In humans they can cause conditions such as CJD. Are prions alive and if so what purpose if any beyond replication do they have? In existential motivation, are our human genes really any different?

Science fiction successfully exploits our ontological insecurity with such ambiguities. For example the protomolecule in TV series The Expanse is a non-life based infectious agent that is said to be “a set of free-floating instructions designed to adapt to and guide other replicating systems”.

Gene image from: https://commons.wikimedia.org/wiki/File:Chromosome_DNA_Gene.svg, Prion image from: https://upload.wikimedia.org/wikipedia/commons/4/45/Major_prion_protein.png, Protomolecule image from: https://expanse.fandom.com/wiki/Protomolecule

It is therefore not inconceivable that any alien pathogen would be bereft of the molecular machinery we currently associate with life. The field of xenobiology attempts to explore fundamentally novel biological systems.

For proteins, in principle, there seems no reason why some of the 20 primary amino acids in life might not be replaced by some of the very large number of alternatives that exist in nature, such as in meteorites (>60 amino acids have been found in certain carbonaceous meteorites).

The similarity of life across the universe (2016)

An intriguing question is how our threshold of what we call life would be influenced if such synthetic nucleic acids (XNA) and subsequent xenobiological systems could be shown to be viable. Advances in synthetic biology may press humanity further into reflecting on how we define ourselves in the context of the universe. One view is that an extraterrestrial organism would be so unlike anything we consider to be life that it would be incompatible as a conventional pathogen. The memorable Star Trek episode ‘The Devil in the Dark’ introduces the audience to the silicon-based organism Horta in a case of ‘It’s life, Jim, but not as we know it.’

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Questions

As a health care worker, how would you approach the medical management of non-carbon based life-form?

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Conversely, if the panspermia hypothesis is indeed correct, it may help explain why many of the aliens in TV shows like Star Trek (Horta being a clear exception) are usually humanoids in appearance. The special effects budget is probably also an important consideration (also see the example of Horta). In the TV series Space: Above and Beyond, the panspermia theory is utilised with an instance of forward contamination, Earth being the origin of bacteria that went onto seed a distant moon following an asteroid collision. This TV show is of additional note as it also questions the life status of androids with artificial intelligence known as Silicates, presumably because they are silicon based rather than their human ‘carbonite’ counterparts.

Regardless of panspermia, perhaps there just is a universal nature conferring a pattern to living matter. We see potential examples here on Earth where significantly different species share common features. Shared biochemical configurations based on efficient energy utilisation with basic building blocks such as carbon may also permit adaptability to new environments and foresee a shared molecular heritage between Earth life-forms and any hypothetical extraterrestrial organisms.

The chemistry and biology of alien life will most likely be the same as that of Earth, because there is only one way to assemble living matter and evolution will ensure that life on exoplanets finds that way.

An Evolutionary Perspective of Neoplastic Diseases in the Universe (2019)

Fibonacci spiral patterns and other “least energy configurations” may spontaneously emerge and self-organise creating phenomenon such as phyllotaxis and highlights a case of convergent evolution.

Fibonacci image from: https://en.wikipedia.org/wiki/File:Fibonacci_spiral_34.svg, Nautilus image from: user Chris 73 and is freely available at //commons.wikimedia.org/wiki/File:NautilusCutawayLogarithmicSpiral.jpg under the creative commons cc-by-sa 3.0 license., Bighorn image from: https://en.wikipedia.org/wiki/File:Ovis_canadensis_2_(cropped).jpg

The idea of such convergence is fascinating when it comes to understanding how we approach the prospect of extra-terrestrial life. Being human myself (and assuming that you are too), one feature that pervades human activity, in particular human medicine is that humans are usually involved. It is perhaps therefore inevitable that we will have human biases when contemplating our existence in the cosmos. But why would any hypothetical astro/exo/xenopathogen specifically target humans rather than any of the other numerous species on Earth?

Anthropocentrism is the viewpoint that human beings are the most important entities in the world and by extension the universe. The Geocentric model of the universe had Earth at its centre and was gradually superseded by the heliocentric model with the Sun at the centre. We now, hopefully, appreciate that humans are not the centre of the universe although it can be hard for us to let go of our cultural egotism. Perhaps one interpretation of panspermia is to give humans a different ancestral heritage that somehow extends across the universe and distracts us from our more immediate and Earthly existential problems.

Anthropocentric thinking can be considered “the tendency to reason about unfamiliar biological species or processes by analogy to humans”. Doctors are guilty of this: consider how we sometimes describe microbes and apply military metaphors in medicine. The universe of the prion is very different to that of the cow.

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Questions

Why would we rationally expect any hypothetical extraterrestrial organism to respond or interact with any facet of human biological life or culture?

Why do we use very human concepts to explain the nature of non-human life?

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Indeed, such a hypothetical pathogen could target any cog within the machine of life that is Earth. In an exponentially unfortuitous turn of events, it may so happen by chance that other dependent life including humans could be secondary victims. A novel organism decimating a critical link(s) in the ecosystem could lead to famine for example. This scenario overlaps with some predictions of climate change; perhaps an example of doomsday scenario convergence.

I started this post by mentioning how this subject would probably be super-niche to most physicians. Yet, now that we have considered some of the issues involved and our anthropocentric biases, there is one important example that I wanted to explore further: the idea that Covid-19 originates from space.

Some authors have proposed that the model of panspermia is the only possible explanation for the appearance of Covid-19 on Earth. One hypothesis is that Covid-19 arrived on a meteorite that struck China with a viral load falling in Wuhan province. Solar activity and sunspot cycles are also implicated in the process with the authors noting a particularly strong cosmic ray spike reported in late November 2019 as being implicated with the emergence of Covid-19:

With the weakening of the magnetic field in the Earth’s vicinity, there would be a high flux of mutagenic cosmic rays [as well as charged dust particles including viruses]. These processes would be likely to herald the onset of new pandemics.

Is the 2019 novel coronavirus related to a spike of cosmic rays? (2020)

In correspondence to the BMJ, the idea of Covid-19 as having an extraterrestrial origin is explained further by the group:

[Covid-19] was initially dispersed in the high atmosphere from a disintegrating cometary bolide. The first major infall of the virus from this primary source in the Hubei province of China would have inevitably led to a massive amplification of the virus in humans, a fraction of which would have been lofted back to the upper atmosphere to be carried in global wind systems across the world… trillions of virions entered the Earth’s upper atmosphere sometime in the latter part of 2019. Virus-laden dust clouds were thereafter able to break through to ground level locations, and spread of the pandemic around the world subsequently occurred through a combination of such infall, viruses transported in global wind systems, and eventually by person-to-person spread.

Rapid Response: Following the science for COVID-19: societal constraints and limitations (2020)

The book Diseases from Space by Hoyle and Wickramasinghe published in 1979 explores the idea of extraterrestrial pathogens. The idea is clearly not limited to Covid-19 but an array of novel diseases that have been suggested as having been introduced from space including very recent ones such as SARS, MERS and Zika virus. Historical examples are not exempt, for example The Plague of Justinian or unexplained outbreaks on sea vessels.

However the great exemplar of the emergence of a new pandemic disease of considerable virulence and pathogenicity was the Spanish Flu Pandemic 1918–1919. That pandemic has been analyzed in great detail … and the astute and engaged reader of all that evidence is left with only one conclusion—the Spanish Flu disease came from Space on a massive scale, and killed tens of millions…

Origin of new emergent Coronavirus and Candida fungal diseases—Terrestrial or cosmic? (2020)

The abrupt appearance of such novel pathogens, particularly where cases have been reported “more or less” simultaneously around the world has been used by proponents of the panspermia hypothesis as suggesting seeding via cosmic (cometary) biologically provenant dust clouds through which the Earth has traversed. They also utilise the model to explain mysterious disease outbreaks (e.g. ships at sea) being caused by atmospheric transmission/global wind systems. Proponents of this idea suggest that if Earth is indeed bombarded by extraterrestrial organisms, then it would have major implications on how we might protect ourselves:

What lessons can we learn? Certainly, near-Earth surveillance of incoming pathogens from space, such as the suggested “Hoyle” shield needs to be an international imperative, as often reiterated by us, including for monitoring for tropospheric global transport of viral plumes as discussed here. But it seems also that once a viral pandemic is already underway, rising viral-plumes from major infected zones can potentially be transported to infect other global regions on a mass scale. Indeed pathogenic re-circulation via the troposphere during a pandemic is a major factor to consider for societies whose thinking seems restricted to “hard lockdowns and social distancing” to prevent or alleviate the spread of airborne viruses.

COVID-19 Sudden Outbreak of Mystery Case Transmissions in Victoria, Australia, May-June 2021: Strong Evidence of Tropospheric Transport of Human Passaged Infective Virions from the Indian Epidemic (2021)

Thus, development of a so called “COVID-19 vaccine” which is much in the news at the time of writing would be a waste of public tax-payer funds if mounted on the scale envisaged by governments and national centers for disease control.

Origin of new emergent Coronavirus and Candida fungal diseases—Terrestrial or cosmic? (2020)

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Questions

Is it irresponsible to publish opinions tacitly posing as irrefutable fact?

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A further postulation is that without a frequent but sporadic influx of genetic material from space, no significant evolution of life would be possible and that terrestrial evolution is “understood properly on the basis of a cosmically derived and interconnected genetic system” and that “life has  been continuously seeded to Earth from the Cosmos”. It can be summed up as follows:

A population of living cellular systems—spores, seeds, even cryopreserved fertilized eggs encased within protective matrices (e.g. interiors of wandering comets, small moons, planetoids, or fragments thereof)—may be dispersed throughout the Cosmos via long space-time journeys (hundreds of millions to billions of years). On landing in a new Cosmic niche a portion or subset of the cells surviving impact adapt rapidly to their new environment primarily via Lamarckian rapid adaptation genetic mechanisms (which may often cause overt disease)

Introduction—Panspermia, 2020 (2020)

There have been a number of critical responses to these ideas, of particular note, there was a flurry within The Lancet following a published letter in 2003 proposing that SARS was from space and the microorganism was present in the stratosphere leading to a fall out over several years. Some selected highlights include:

First, the extraterrestrial source of DNA/RNA-based life must sustain ecological conditions similar to Earth, allowing for cellular growth and divisions to create a continuous flow of viable cells and viruses to Earth… The similarity in DNA sequences between the space- derived cells and microorganisms found on Earth presuppose the latter to have derived from space fairly recently… Second, specialised pathogens must have extraterrestrial hosts similar to those on Earth, such as vertebrates, to evolve and survive. Third, the extraterrestrial source must be quite close to Earth, since vertebrate-specific RNA viruses can only survive hours to days outside of their hosts. Finally, any space-derived life needs to cope with high degrees of ultraviolet radiation in the stratosphere known to modify cellular DNA/RNA in a lethal manner.

Willerslev, Hansen, Rønn, Nielsen (2003)

If life exists elsewhere in the Universe, it is extremely unlikely that it would have independently evolved macro- molecules, such as 16S rRNA, or other intracellular components homologous to those of their terrestrial counterparts. This would be especially true of viruses, whose dependence on the intracellular molecular machinery of their hosts to complete their biological cycles would make their survival and evolution within the terrestrial biosphere unlikely should they have an independent, extra- terrestrial origin.

Ponce de Leon, Lazcano (2003)

If SARS came from space, cases of the disease should have occurred independently and concurrently in more than one location on our planet. The fact is that all cases (without exception) can be traced to a single location of an extremely small size in China. …SARS is a coronavirus. No such virus—or for that matter any RNA virus—unlike bacteria, is known to be resistant to the kind of radiation present in space.

Bhargava (2003)

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Questions

What factors make something more likely to be published in the medical literature?

What factors make something more likely to be reported by the popular media?

How can I subscribe to the International Journal of Non-Significance?

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I explained at the beginning of this post that I personally don’t believe that pathogens such as Covid-19 are from space. I also feel it is important to allow an open discussion and explore ideas and refute them when appropriate. There is however a counter-argument to suggest that some ideas might be harmful if given the oxygen of debate. I will leave it to my astute and engaged readership to formulate their own ideas regarding the issues explored in this post.

Biases toward spectacular media are also important: there is a tendency for the sensationalisation of scientific findings and the showcasing of heterodoxy, if only to encourage polarising criticism and/or act as unhelpful but financially driven clickbait. These issues do have an effect on health care; consider how patients may seek advice regarding health issues reported in the media or how healthcare workers have to navigate the potential publication biases of medical research. With the Covid-19 pandemic, many of these issues have coalesced and clinicians can no longer neatly compartmentalise nor ignore them.

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Questions

Should physicians engage with the media in the public refutation or support of unorthodox theories or does this do more harm than good?

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My opinion is that the extraterrestrial introduction of pathogens would have to consider not only such an organism reaching our solar system in an hostile universe but also surviving the friction of Earth entry. It must additionally reach the Earth at a time when a potential host is not only present but also sufficiently evolved to a point where a pathogen-host interaction can be facilitated. Moreover, such a hypothetical pathogen would have had to independently evolve outside of the Earth environment but still develop molecular parallels to the complex biochemical machinery of Earth life. Furthermore, if it is a dangerous pathogen we are considering, it must then also have the potential physiological effect of causing disease in the host in addition to its usual nature.

Consider the analogy of a constantly changing key encountering and then somehow being immaculately responsive to a constantly changing lock in a potentially infinite and timeless universe where there may not even be a key or lock maker. Convergent molecular and evolutionary pathways may offer a partial counterargument as some kind of cosmic skeleton key, but the chances still feel (wait for it…) astronomically small.

Of course, all of this presupposes the monumental assumption that life in the universe outside of Earth’s sphere even exists. The panspermia hypothesis is a fascinating one but it is seems easy for some to conflate a potential one-off seeding event with the idea of repeated (even continual) extraterrestrial exposures as the trigger for multiple modern pandemics. Does the idea of a panspermic introduction of pathogens merely represent a modern iteration of the Aristotelian theory of generatio spontanea?

The authors of the original letter in The Lancet regarding SARS end their reply to the criticism with “All the correspondents seem determined to attack panspermia. The evidence will eventually accumulate to show who is right.” What do you think? Please consider sharing your thoughts in the comments section below.

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Summary

The concept of alien pathogens feels rather abstract to many physicians, yet within the topic we can consolidate our understanding of disease, life and what it means to be human. The potential for back-contamination of the Earth with our increasing ventures into Space is a serious but albeit seemingly unlikely one. Potential comparisons can be made with the various historical examples where an Earth originating pathogenic organism has caused decimation when transplanted elsewhere. This intraworld invasion is based on the exploitation of a shared molecular and evolutionary heritage. It would be difficult to permit this kind of home advantage to an extra-terrestrial organism. Even with the concept of panspermia, the likelihood of essentially a perfectly adapted pathogen reaching not just Earth through the vast hostility and temporally ambiguous universe but our Earth at precisely the right time seems astronomically small. The invariably (and arrogant) anthropocentric target of these hypothetical extra-terrestrial organisms is not only embedded in the science-fiction of our time but also in some of our scientific literature. Understandably the hypothesis can fascinate and question the very idea of pathogenicity along the molecular basis of what it means to be alive and human. This is perhaps both the allure and the absurdism of otherly life. Physicians have found themselves in a position where they not only have to explain health and disease to patients based on a reasonable understanding of basic sciences but also in a manner that uses the cultural apparatus at their disposal.

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Further resources

Immune recognition of putative alien microbial structures: Host–pathogen interactions in the age of space travel
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6991955/

Microbial pathogenicity in space
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8069885/

The similarity of life across the universe
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4865312/

An evolutionary perspective of neoplastic diseases in the universe
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6456284/