by Stephen Fleischfresser
April 24, 2018
start and end with the octopus.
revives the oft-mocked theory
that life on Earth began
in a rain of cosmic microbes...
The peer-reviewed journal Progress in Biophysics and Molecular Biology recently published a most remarkable scientific paper: Cause of Cambrian Explosion - Terrestrial or Cosmic.
With 33 authors from a wide range of reputable universities and research institutes, the paper makes a seemingly incredible claim.
A claim that if true, would have the most profound consequences for our understanding of the universe. Life, the paper argues, did not originate on the planet Earth.
The response? Near silence...
The reasons for this are as fascinating as the evidence and claims advanced by the paper itself. The publication revives a controversial idea concerning the origin of life, an idea stretching back to Ancient Greece, known as panspermia.
The scientific orthodoxy concerning the origin of life is called abiogenesis.
This suggests that at some point in the earth's early history, conditions were favorable for the creation of complex organic chemistry that, in turn, led to the self-organization of the first primitive life forms.
Much is understood about the process, but exactly how information came to be coded in nucleic acids (DNA and RNA) to form the system of genetic inheritance and expression, and how this transformed into life itself, remains unknown.
The other slightly uncomfortable aspect of the abiogenic account is that it seems to take place in a surprisingly short amount of time.
The theory requires that the "primordial soup" from which self-replicating RNA emerged formed within an 800 million year period following the stabilization of the Earth's crust, a timeframe some researchers think is too narrow.
Despite its drawbacks and lack of detail, abiogenesis is the consensus, the only plausible hypothesis for the origin of life.
The panspermia hypothesis, however, disputes nearly every aspect of this story.
Of the 33 authors, Edward Steele and Chandra Wickramasinghe are the most well-known.
Astronauts working on the exterior
of the International Space Station,
which research has found to be
covered in bacteria.
Hoyle and Wickramasinghe developed the model of panspermia at the center of the recent study.
The new paper is a review of,
The H-W model holds, the authors state,
In other words, the researchers suggest that abiogenesis did not happen on Earth and the main source of genetic novelty is not caused by the selection of naturally occurring advantageous mutations, but rather comes from a rain of extra-terrestrial living matter that integrates itself, via neo-Lamarckian mechanisms such as horizontal gene transfer, into the genomes of terrestrial life.
Beyond this, the model also postulates that various epidemics are caused by the arrival of viruses from space and that extra-terrestrial retroviruses drove the Cambrian explosion.
Not to mention that the octopus might well be an alien.
One might be tempted to laugh, if it weren't for the volume of titillating evidence they present, and the nagging worry that the naysayers have been wrong before.
But just because theories seen as crackpot by the 'scientific establishment' have later been vindicated, does not necessarily mean that is the case here.
The proof advanced,
In other words, the argument advanced by Steel and colleagues in plausible, but not convincing.
Nonetheless, the paper has withstood a year of intense peer review.
As Steele points out to Cosmos,
The tension between the evidence and the claims based on it make for uneasy reading.
Just as the field of Alzheimer's research ponders if its main theory of many decades is wrong, perhaps it is worth entertaining a quaint notion:
The paper is remarkable in tone.
Far from the cautious claims of normal scientific literature, it is almost triumphant.
The evidence is enough to back their confidence, fascinating and detailed.
Central to their paper, and indeed their model of panspermia, is the action of viruses, retroviruses, in particular, and much of the evidence presented revolves around them.
Retroviruses are fiendishly clever.
Intriguingly, if they infect germline cells, sperm or ova, for example, then the organism will transmit the integrated retrovirus, known as a provirus, to their descendants.
In other words, the acquired genetic material becomes part of the offspring's inheritance. It's a solidly Lamarckian mechanism and Steele's own somatic selection hypothesis is based on such viral capacities.
This ability to affect the genetic makeup of their hosts makes viruses a force to be reckoned with.
As a group of researchers, led by microbiologist Matthew B. Sullivan, wrote in 2016,
And the truth is there are a lot of viruses around.
Virologist Curtis Suttle from the University of British Columbia in Canada and his colleagues last year published the first research into the number of viruses being deposited from the atmosphere. The amount is staggering, possibly billions a day for every square meter of the earth.
Steele and colleagues seem to have been finally spurred to action by new virological data connecting viruses and evolution.
They also established that the two entities demonstrate patterns of co-speciation:
This, claim Steele and colleagues, is a key prediction of the H-W panspermia hypothesis.
Steele and colleagues derive two points from Aiewsakun and Katzourakis' findings.
The first is that viruses are successful only because they have evolved to make use of the host's cellular machinery and genetic regulatory make-up - that is, they are,
Given this, evidence that retroviruses emerged at the same time as, and co-speciated with, their hosts, simply doesn't add up.
Retroviruses are carefully adapted to the stable make-up of their target hosts and such co-variance just shouldn't happen.
The second point is that the emergence of these retroviruses barely predates the Cambrian Explosion, a period in which sudden and unparalleled biological diversity and complexity appeared on Earth.
They also emerge not long after a mass extinction event at the end of the Ediacaran period, 542 million years ago.
Panspermia accounts for all this, the authors explain, thus:
All life, both terrestrial and extra-terrestrial, is related, according to this view, as all life comes from the greater biosphere in which genetic material in the "cosmic gene pool" is readily shared.
There is an underlying biochemical unity of all life, differing only in which isotopes of essential elements life from different parts of the universe might use.
One of the loudest champions
of panspermia theory,
the late astronomer, Fred Hoyle.
As Wickramasinghe puts it,
One of the reasons for adopting panspermia, he explains, is the,
The idea that abiogenesis occurred on the cosmically insignificant earth in an awkwardly short amount of time strikes him as improbable, at best.
Steele and colleagues argue that abiogenesis is deeply unlikely here on earth and that,
Despite this, Wickramasinghe, Hoyle and Steele have all entertained the notion that there is no need for such a creation story.
When asked if there must be abiogenesis at some point, somewhere in the universe, Steele replies,
The reason for this, and a common factor amongst the three scientists, is a commitment to, or interest in, the steady state theory of cosmology.
The idea, first put forward by Hoyle and two colleagues in 1948, holds that the universe has no beginning or end and remains the same size.
As matter at the outer reaches of the universe loses energy and goes dark, new matter is created.
In this view, biology is as timeless and without origin as the universe itself. Hoyle famously lost the fight over cosmological models to George Gamow and the advocates for the Big Bang.
Despite the discovery of cosmic microwave background radiation in 1964, something predicted by Big Bang theory, Hoyle never recanted his beliefs, and the steady state universe seems an underlying presence in the H-W model of panspermia.
The background theories and characters may be unsettling, but they don't detract from the evidence upon which the paper rests, which must be taken on its own terms. Much of it is peer reviewed, but it is not always as persuasive as billed. Nonetheless, there is a good deal that gives one pause for thought.
Viking's results pointed to something with a metabolism in the Martian soils, but then couldn't detect any organic material. The result is interesting, but inconclusive.
The authors also insist fossil microbes have already been found in various meteorites, including the famous Murchison meteorite that fell in Victoria, Australia, in 1969. While they point to refereed journal articles for support, it seems the jury is still out.
Once again, the evidence is tantalizing but not conclusive.
More recently, traces of seemingly biological carbon deposits have been found in rocks predating the emergence of life, during a period of heavy comet and asteroid bombardment.
The authors see this as evidence of life carried to earth, but, as Baverstock suggests, there are other reasons such carbon might be there.
More intriguing is the discovery of bacteria and microbes in unlikely places, such as the stratosphere, 30 to 40 kilometers above the surface of the planet, and more excitingly on the outside of the International Space Station.
In the case of the ISS, contamination has been ruled out and the physics suggests that it is not possible for the microbes to have been lofted up from the earth's surface.
This finding coincides nicely with Hoyle and Wickramasinghe's demonstration that interstellar dust is partly made of organic molecules. Perhaps the most intriguing astronomical evidence of all is that which converted Steele to the panspermia hypothesis.
A development from the research into organic interstellar dust, the spectrum of light produced as infra-red radiation passes through cosmic dust turns out to have the exact same spectral signature as freeze-dried E. coli bacteria.
Steele's frustration with the scientific community's indifference to this staggering result is palpable.
So why has the result largely been passed over as 'a curiosity'...?
Perhaps the most controversial aspect of the new paper concerns the origins of the octopus.
The discussion begins, as it so often does in the paper, with some intriguing evidence.
And they may have a point...
But here things get weird.
It's moments like this that point to the source of the paper's unease.
The evidence is nonetheless provocative.
Taken together it indicates, if nothing else, that there is much we don't know and that our prevailing scientific orthodoxies will undergo transformations, as all scientific theories do.
The orthodox scientific response is encapsulated in the commentary from the decorated virologist Karin Moelling of the Max Planck Institute Molecular Genetics, in Berlin, and Institute of Medical Microbiology, Zürich, published in the same journal issue.
Scientific commentary is muted, confused by the tension between the outlandish claims and the peer-reviewed status of the paper.
Maybe we should side with sage advice of the journal's editor, the renowned British biologist Denis Noble.
The authors, too, think this the best course of action.
Instead of dismissing panspermia out of hand, perhaps then, we should just wait for the discoveries that future space probes might bring.
Evidence, as always, will be the ultimate decider...