A few years ago I wrote an article for Cryptid Culture magazine #7 about the microbial cryptids that may be lurking all around us. Since the magazine has been defunct for a while now, I thought I'd post that article in full here.
You can still purchase copies of Cryptid Culture from Blurb. Definitely check it out. There were some great articles.
THE SHADOW BIOSPHERE
In our search for unknown creatures we often focus on large,
impressive cryptids- Mothman, Sasquatch, the Jersey Devil, Nessie. Beasts that,
if they do exist, would be extremely rare and inhabit the periphery of
humanity’s territory.
But what if there are uncountable hordes of unidentified
organisms all around us? What if they are in the soil beneath our feet? In the
damp spots in our basements? Even lurking inside our very bodies? What if there
are whole unknown domains of life whose existence we have never even suspected
because they are too small to be seen with the naked eye and so radically
different from conventional Earthly life that we do not even have the proper
tools to detect them? What if there is an entire Shadow Biosphere (a term
originally coined by researchers Carol Cleland and Shelley Copley of the
University of Colorado in 2005) lurking all around us?
The exact origin of life on Earth is not currently known,
though scientists have posed many possibilities. Some have speculated that life
coalesced out of the mineral-rich waters around hot springs or deep-sea
hydrothermal vents. Others have wondered if the basic building blocks of life
arose in warm tidal pools or on the surface of carbon-based matter floating in
droplets of sea spray. Still others have wondered if the components of life
might have been brought to Earth on icy comets. It’s possible- even likely-
that simple life arose multiple times and in multiple forms in these and many
other crucibles on the early Earth.
At some point, though, one type of life predominated and
took over every ecological niche on the planet. This kind of life is highly
plastic in the form it takes: bacteria, amoebae, algae, jellyfish, dinosaurs,
humans. Organisms very different in form and structure, yet all sharing the
same fundamental building blocks. Their genetic information is wrapped up in
double-helices of DNA constructed from four bases: guanine, cytosine, adenine
and thymine . Their bodies are built and controlled by proteins and enzymes
made of 20 different amino acids. And many of their support structures- hair,
wood, cell membranes, etc- are constructed from carbohydrates.
But what if other life forms made from different sets of
building blocks also developed in those dawn crucibles? What if they used a molecular
structure besides DNA to hold genetic information? What if they utilized more
than the familiar 20 amino acids to build their proteins? Or a different set of
amino acids entirely? Even if such organisms did evolve they must surely have
gone extinct early on, out-competed by life that dominates the Earth today?
Otherwise we surely would have found evidence of them.
Perhaps not, though. The majority of living things on Earth
are prokaryotes- unicellular microbes too small for us to see with the naked
eye. Under a microscope, most
prokaryotes look fairly similar. Their cells are either shaped like pills,
spheres or twisting corkscrews. You can’t tell what species a prokaryote is
just by looking at it.
But this external simplicity and uniformity hides a universe
of metabolic diversity. Some prokaryotes can photosynthesize like plants. Some
can obtain energy from salt or sulfur. Some live off metals or oil. Some even
feed on radioactive materials like uranium.
And of course, there are the more commonly known microbes that
parasitize other living organisms. To identify prokaryote species, scientists
have developed tools and techniques to detect the various enzymes, chemicals,
and other molecular components that allow them to live and feed in these unique
ways. Additionally, since prokaryotes are so small and numerous, these
techniques are not performed on individual specimens. Instead, they are tested
in a “shotgun” fashion on a sample of, say, soil or pond water to detect the
overall presence and abundance of certain metabolic components. These techniques assume, however, that the
organisms being examined are composed of the DNA, proteins, and other building
blocks of regular terrestrial life. They
would not find denizens of the Shadow Biosphere if their structures and genetic
material are different from what we currently know.
There is actually a precedence for discovering a completely
new domain of life. Up until the late 1970s all life on Earth was placed into
two broad categories based on the structure of their cells. Eukaryote cells
have lots of smaller metabolism-performing structures called organelles inside
them, including a nucleus to contain DNA, mitochondria to generate energy, and,
in the case of plants and algae, chloroplasts to photosynthesize. All animals,
plants, algae, fungi, and many single-celled organisms such as diatoms,
paramecia, and amoebae are eukaryotes.
The aforementioned prokaryotes, by contrast, have no
organelles. Their DNA and all metabolic enzymes float freely in the cell. For decades all prokaryotes were assumed to
be bacteria. In the late 1970s, however, researchers noticed that some
prokaryotes had proteins and other chemical structures that were vastly
different from those found in the majority of these microbes. What’s more,
these strange prokaryotes were genetically closer to each other than they were
to any other bacteria. It soon became clear that these organisms were a whole
new domain of life that researchers dubbed the Archaea.
It’s important to note that even though archaea differ from
eukaryotes and bacteria in some structural ways, they still utilize DNA and the
20 amino acids found in the other two groups.
Archaea may have evolved separately from the other domains, but they are
still ultimately descended from the same distant ancestor as the others. They
are not part of a Shadow Biosphere. The point of this story is to illustrate
the fact that that unique microbial organisms can indeed be lurking all around
us without being detected.
So, is there any
evidence for a Shadow Biosphere? One possible clue to their presence is a
phenomenon known as desert varnish. In arid regions around the world, exposed
rock outcroppings frequently develop a thin red or black coating of iron,
manganese, silica and clay particles. Native peoples around the world have
created petroglyph images on these rocks by scrapping away this thin dark
patina to expose the lighter rock underneath. Though desert varnish has been extensively
studied, its exact origins are not known. Many scientists think it is caused by
chemical weathering or by the slow action of bacteria or archaea living on the
surface of the rocks. Some, though, have suggested that the dark patinas could
have been deposited by the unknown organisms of the Shadow Biosphere. Testing
this hypothesis would require developing techniques, which I will discuss a
little later, to detect traces of non-traditional life forms.
It’s possible that some of these Earthly aliens have
actually been found. In 1996 geologist Phillipa Uwins and her team discovered
microscopic filament-like structures on pieces of freshly fractured sandstone
they had pulled from 2-3 miles below the ocean floor. Soon, the filaments,
which Uwins dubbed “nanobes”, were found
to be growing on equipment and containers in her lab that had come into contact
with the samples. Experimentation found that the nanobes would also grow and
even multiply on freshly fractured rock samples. Testing with DAPI staining- a
technique for finding double stranded nucleic acids like DNA- produced a strong
positive result, indicating that these filaments had genetic material and were
thus alive. That revelation created
quite a conundrum, though, because these nanobes were one-tenth smaller than
even the smallest known bacteria or archaea. At that size, a conventional
organism would simply be too small to contain the genetic material and proteins
necessary for life. Could nanobes have different chemical structures for
carrying out life’s functions? Uwins and her colleagues are still hesitant to
definitively claim nanobes are a new form of life, or even alive at all. More
research is required to determine the exact nature of these structures. Nevertheless, they are another tantalizing
clue to the existence of an unsuspected Shadow Biosphere lurking all around
us.
All this speculation begs the question: how would one find
evidence of the Shadow Biosphere if its denizens cannot be detected by techniques
that target known Earth life? One possibility would be to develop experiments
that look for other amino acids in the environment beyond the familiar 20.
Another possible method would be to develop a chemical reagent that can
distinguish between typical DNA and other genetic material that might have
different bases besides guanine, cytosine, adenine, and thymine. This reagent
could be used to stain a sample of cells gathered from, say, a soil sample. Any
cells that were not stained could potentially possess a gene-encoding structure
different from typical DNA.
As I stated at the beginning, while the big, bizarre
cryptids like Mothman and Thunderbirds may be the most popular, some of the
strangest, truly unique organisms on Earth may be lurking under our very feet
beyond the limits of what our eyes and scientific instruments can see. The
trick to finding them may require looking beyond what we currently understand
as life on this planet.
SELECTED REFERENCES
Cleland, C. E. (2007). Epistemological issues in the study
of microbial life: Alternative terran biospheres? Studies in History and
Philosophy of Science Part C: Studies in History and Philosophy of Biological
and Biomedical Sciences, 38(4), 847-861.
Cleland, C. E., & Copley, S. D. (2005). The
possibility of alternative microbial life on Earth. International Journal of
Astrobiology, 4(3 & 4), 165-173.
Uwins, P. J. R., Webb, R. I, & Taylor, A. P. (1998).
Novel nano-organisms from Australian sandstones. American Mineralogist, 83(11-12,
Part 2): 1541-1550.
