Speaker 1: Welcome to Stuff to Blow Your Mind, a production of
Speaker 1: I heeart Radio. Hi. My name is Joe McCormick, and
Speaker 1: this is the Artifact, a short form series from Stuff
Speaker 1: to Blow Your Mind, focusing on particular objects, ideas, and
Speaker 1: moments in time. On the western coast of Australia, there's
Speaker 1: a place called Shark Bay, and within Shark Bay there's
Speaker 1: a nature reserve known as Hamlin Pool. Today you can
Speaker 1: walk out over a wooden jetty at Hamlin Pool to
Speaker 1: see the shallows up close. Down below, there are hundreds
Speaker 1: of strange, bulbous mineral formations peeking up over the water
Speaker 1: line or sitting just below it. It's hard to describe
Speaker 1: exactly what they look like. Black stone broccoli perched upright
Speaker 1: in the still water, atomic mushroom clouds frozen in place,
Speaker 1: or dark pebbly brains flocking out of the Indian Ocean.
Speaker 1: These are stromatolites. If you stand on the jetty at
Speaker 1: Hamlin Pool looking out at this army of mineral bulbs,
Speaker 1: you're getting a pretty close approximation of what most visible
Speaker 1: life on planet Earth looked like for something like eighty
Speaker 1: percent of its history. Because while these are mineral formations,
Speaker 1: They're not just dead rock, they're alive and growing. Stromatolites
Speaker 1: are one type from a class of mineral formations called microbiolites,
Speaker 1: natural stone monuments that are built by microscopic organisms, and
Speaker 1: not all of them look like the columns of mushroom
Speaker 1: brain broccoli at Hamlin Bay. Some microbiolites are flat, some
Speaker 1: are domed, and some form ascending pillars with different shapes
Speaker 1: and contours. Though there are lots of microbiolites in the world,
Speaker 1: there are only a handful of places left where you
Speaker 1: can find true marine stromatolites growing in the wild. So
Speaker 1: what makes us stromatallite special. The word stromatallite means layered rock.
Speaker 1: If you look at a cross section, you can see
Speaker 1: banded strata within them extremely thin layers of mineral deposition,
Speaker 1: kind of like a stone puff pastry, with the layers
Speaker 1: sometimes alternating between light and dark. And these layers actually
Speaker 1: tell us something about the process that created them. Stromatallites
Speaker 1: are built by microscopic organisms like photosynthetic cyanobacteria also known
Speaker 1: as blue green algae. These are single celled life forms
Speaker 1: that can be found almost everywhere on Earth, especially in
Speaker 1: the water. Cyanobacteria like plants, survived by using energy from
Speaker 1: the sunlight to convert carbon dioxide from the environment into food.
Speaker 1: Though cyanobacteria existed for billions of years before the first
Speaker 1: plants evolved, without them, you never would have been born.
Speaker 1: As Earth's first photosynthesizers, microbes like cyanobacteria converted the planet's
Speaker 1: early atmosphere into what it is today by polluting it
Speaker 1: with their metabolic waste product, which is oxygen. Every animal
Speaker 1: that ever lived could only evolve because of what the
Speaker 1: early photosynthesizers did to the atmosphere. So for billions of years,
Speaker 1: these microbes dominated planet Earth, changing the composition of the
Speaker 1: air and leaving behind their stromatolite mineral formations in the
Speaker 1: fossil record. But to come back to the question about
Speaker 1: how they form, where do these layers of strata and
Speaker 1: the stromatalite come from. Microbes like cyanobacteria don't just float
Speaker 1: around by themselves. When they're able, they glom onto other
Speaker 1: micro organisms to form what are known as biofilms or
Speaker 1: microbial mats. Think of a kind of thin, sticky carpet
Speaker 1: in which billions of microbes glue themselves both to one
Speaker 1: another and to an underlying surface with the help of
Speaker 1: a class of biological cement known as extracellular polymeric substances
Speaker 1: or e p s s. These microbial mats, being sticky
Speaker 1: by evolutionary design, don't just stick to the underlying substrate.
Speaker 1: They also act kind of like a glue trap, catching
Speaker 1: hold of tiny grains of sediment and sand that wash
Speaker 1: over the surface of the mat due to the tide
Speaker 1: or other mechanical forces. Over the years, layer by layer,
Speaker 1: these sticky mats of biological material trapped sediment and also
Speaker 1: calcium carbonate harden into solid mineral formations like the columns
Speaker 1: at Shark Bay, always climbing up higher like the crown
Speaker 1: of a tree in the forest, to move towards the
Speaker 1: sunlight that feeds them. If you look at the history
Speaker 1: of earth life in the fossil record from roughly three
Speaker 1: and a half billion years ago until about one billion
Speaker 1: years ago, stramatallites absolutely dominate the scene, gathering in shallow
Speaker 1: sea ease and across continental shores around the world. But
Speaker 1: around a billion years ago, the finally layered stramatallites start
Speaker 1: to vanish from the geological record, and they've remained rare
Speaker 1: until today. What happened to them. There are several possibilities,
Speaker 1: but one interesting investigation into this question was a study
Speaker 1: published in in p N A S by Joan M.
Speaker 1: Bernhardt at All. This study picks up from the observation
Speaker 1: that at around the same time stramaatellites began to decline
Speaker 1: in the fossil record, they seem to be replaced with
Speaker 1: a different kind of microbial matt formation called a thrombo lighte.
Speaker 1: Whereas stramatolites are layered rocks, thrombo lights are clotted rocks
Speaker 1: with a microstructure to match their name. So did most
Speaker 1: of the world stromatallites become thrombo lights and if so why?
Speaker 1: The researchers behind this study suggest that thenswer to the
Speaker 1: question may lie in the evolution of another organism known
Speaker 1: as foraminifera. Foraminifera, often shortened to four ams, are a
Speaker 1: type of single celled eukaryotic organism from the Kingdom of
Speaker 1: life known as the protests. Along with organisms like amibas
Speaker 1: and the Plasmodium parasite that causes malaria. You can find
Speaker 1: for Aminifera throughout the ocean, often in seafloor sediments, where
Speaker 1: they use amazing and fantastically creepy, shape shifting tendrils called
Speaker 1: pseudopods to reach out into their surroundings and snatch up food.
Speaker 1: For Aminifera build tiny shells for themselves called tests, and
Speaker 1: they first evolved roughly around the time the stramatallites were
Speaker 1: declining and the thrombo lights began to rise, so it
Speaker 1: makes sense to wonder if they had something to do
Speaker 1: with the change in Earth's microbial lites. The authors of
Speaker 1: study wanted to see if the presence of for Aminifera
Speaker 1: in a living stormatellite would have a noticeable effect on
Speaker 1: how new mineral layers were accumulated, so they took modern
Speaker 1: living stormatellites from a place called high Born Key in
Speaker 1: the Bahamas and seeded them with foams. Some of the
Speaker 1: test samples were treated with a drug that would inhibit
Speaker 1: the function of the forum pseudopods, while others were left untreated.
Speaker 1: After about six months, they found that the presence of
Speaker 1: functional forums could absolutely affect the structure of the stormatallites.
Speaker 1: In samples where the foreams had been drugged, thin layers
Speaker 1: were visible. In the samples where the forearms were allowed
Speaker 1: to do their thing, the stramatallites had assumed the clotted
Speaker 1: structure seen today in thrombolites. Altogether, this is taken as
Speaker 1: evidence that the forum and if um may have had
Speaker 1: something to do with the stormatellites decline. Today, you can
Speaker 1: only find living stramatallites in special places, usually places with
Speaker 1: water that has a very high salinity, like evaporating salt
Speaker 1: water pools and tidal areas. I kept thinking about how
Speaker 1: in this way stramatollites have something in common with sauerkraut.
Speaker 1: Lacto fermented foods like sauerkraut and kimchi are made by
Speaker 1: salting vegetables and packing them down in a wet, anaerobic environment.
Speaker 1: The reason the vegetables turn nice and sour instead of
Speaker 1: simply rotting is that the salty wet conditions in the
Speaker 1: jar inhibit the growth of microbes and mold that cause spoilage,
Speaker 1: but allow the growth of salt tolerant lactic acid bacteria.
Speaker 1: As the lactic acid bacteria thrive, they produce acid as
Speaker 1: a byproduct of their metabolism, which lowers the pH of
Speaker 1: the fermentation, further preventing other microbes from surviving and creating
Speaker 1: the sour flavors we love. Wild stramatollites today tend to
Speaker 1: survive in high salinity environments where organisms that would otherwise
Speaker 1: graze on the exposed mats and eat them up just
Speaker 1: can't tolerate the salt. Tune into new editions of the
Speaker 1: artifact Free Wednesday, hosted either by Robert or myself. As always,
Speaker 1: you can email us at contact at stuff to Blow
Speaker 1: your Mind dot com. Stuff to Blow your Mind is
Speaker 1: a production of I Heart Radio. For more podcasts for
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