WEBVTT - The Artifact Redux: Stone Mushroom Clouds 0:00:03.279 --> 0:00:05.640 Welcome to Stuff to Blow Your Mind, a production of 0:00:05.640 --> 0:00:11.080 I heeart Radio. Hi. My name is Joe McCormick, and 0:00:11.200 --> 0:00:14.640 this is the Artifact, a short form series from Stuff 0:00:14.680 --> 0:00:18.560 to Blow Your Mind, focusing on particular objects, ideas, and 0:00:18.680 --> 0:00:24.200 moments in time. On the western coast of Australia, there's 0:00:24.239 --> 0:00:28.040 a place called Shark Bay, and within Shark Bay there's 0:00:28.080 --> 0:00:32.120 a nature reserve known as Hamlin Pool. Today you can 0:00:32.159 --> 0:00:34.920 walk out over a wooden jetty at Hamlin Pool to 0:00:34.960 --> 0:00:39.680 see the shallows up close. Down below, there are hundreds 0:00:39.720 --> 0:00:44.520 of strange, bulbous mineral formations peeking up over the water 0:00:44.640 --> 0:00:47.840 line or sitting just below it. It's hard to describe 0:00:47.840 --> 0:00:52.680 exactly what they look like. Black stone broccoli perched upright 0:00:52.720 --> 0:00:57.200 in the still water, atomic mushroom clouds frozen in place, 0:00:57.920 --> 0:01:01.560 or dark pebbly brains flocking out of the Indian Ocean. 0:01:02.920 --> 0:01:06.640 These are stromatolites. If you stand on the jetty at 0:01:06.640 --> 0:01:10.039 Hamlin Pool looking out at this army of mineral bulbs, 0:01:10.440 --> 0:01:14.480 you're getting a pretty close approximation of what most visible 0:01:14.560 --> 0:01:18.160 life on planet Earth looked like for something like eighty 0:01:18.280 --> 0:01:22.679 percent of its history. Because while these are mineral formations, 0:01:22.720 --> 0:01:28.440 They're not just dead rock, they're alive and growing. Stromatolites 0:01:28.480 --> 0:01:32.840 are one type from a class of mineral formations called microbiolites, 0:01:33.480 --> 0:01:38.080 natural stone monuments that are built by microscopic organisms, and 0:01:38.160 --> 0:01:40.800 not all of them look like the columns of mushroom 0:01:40.920 --> 0:01:45.880 brain broccoli at Hamlin Bay. Some microbiolites are flat, some 0:01:46.000 --> 0:01:50.040 are domed, and some form ascending pillars with different shapes 0:01:50.040 --> 0:01:54.000 and contours. Though there are lots of microbiolites in the world, 0:01:54.080 --> 0:01:56.960 there are only a handful of places left where you 0:01:56.960 --> 0:02:01.960 can find true marine stromatolites growing in the wild. So 0:02:02.080 --> 0:02:07.320 what makes us stromatallite special. The word stromatallite means layered rock. 0:02:08.000 --> 0:02:10.160 If you look at a cross section, you can see 0:02:10.240 --> 0:02:15.480 banded strata within them extremely thin layers of mineral deposition, 0:02:15.960 --> 0:02:19.280 kind of like a stone puff pastry, with the layers 0:02:19.320 --> 0:02:23.840 sometimes alternating between light and dark. And these layers actually 0:02:23.880 --> 0:02:27.760 tell us something about the process that created them. Stromatallites 0:02:27.800 --> 0:02:33.280 are built by microscopic organisms like photosynthetic cyanobacteria also known 0:02:33.320 --> 0:02:37.600 as blue green algae. These are single celled life forms 0:02:37.639 --> 0:02:40.720 that can be found almost everywhere on Earth, especially in 0:02:40.760 --> 0:02:46.000 the water. Cyanobacteria like plants, survived by using energy from 0:02:46.040 --> 0:02:50.640 the sunlight to convert carbon dioxide from the environment into food. 0:02:51.280 --> 0:02:55.400 Though cyanobacteria existed for billions of years before the first 0:02:55.440 --> 0:02:59.120 plants evolved, without them, you never would have been born. 0:02:59.840 --> 0:03:05.600 As Earth's first photosynthesizers, microbes like cyanobacteria converted the planet's 0:03:05.600 --> 0:03:09.320 early atmosphere into what it is today by polluting it 0:03:09.360 --> 0:03:13.840 with their metabolic waste product, which is oxygen. Every animal 0:03:13.919 --> 0:03:17.320 that ever lived could only evolve because of what the 0:03:17.360 --> 0:03:23.520 early photosynthesizers did to the atmosphere. So for billions of years, 0:03:23.560 --> 0:03:27.760 these microbes dominated planet Earth, changing the composition of the 0:03:27.800 --> 0:03:31.920 air and leaving behind their stromatolite mineral formations in the 0:03:31.960 --> 0:03:35.240 fossil record. But to come back to the question about 0:03:35.240 --> 0:03:38.560 how they form, where do these layers of strata and 0:03:38.600 --> 0:03:42.920 the stromatalite come from. Microbes like cyanobacteria don't just float 0:03:42.960 --> 0:03:46.880 around by themselves. When they're able, they glom onto other 0:03:46.960 --> 0:03:50.480 micro organisms to form what are known as biofilms or 0:03:50.600 --> 0:03:54.880 microbial mats. Think of a kind of thin, sticky carpet 0:03:54.960 --> 0:03:58.760 in which billions of microbes glue themselves both to one 0:03:58.760 --> 0:04:02.240 another and to an underlying surface with the help of 0:04:02.280 --> 0:04:07.280 a class of biological cement known as extracellular polymeric substances 0:04:07.360 --> 0:04:11.240 or e p s s. These microbial mats, being sticky 0:04:11.320 --> 0:04:15.120 by evolutionary design, don't just stick to the underlying substrate. 0:04:15.520 --> 0:04:18.520 They also act kind of like a glue trap, catching 0:04:18.600 --> 0:04:22.159 hold of tiny grains of sediment and sand that wash 0:04:22.240 --> 0:04:24.880 over the surface of the mat due to the tide 0:04:25.000 --> 0:04:29.239 or other mechanical forces. Over the years, layer by layer, 0:04:29.800 --> 0:04:33.960 these sticky mats of biological material trapped sediment and also 0:04:34.080 --> 0:04:38.960 calcium carbonate harden into solid mineral formations like the columns 0:04:39.000 --> 0:04:42.400 at Shark Bay, always climbing up higher like the crown 0:04:42.440 --> 0:04:45.080 of a tree in the forest, to move towards the 0:04:45.120 --> 0:04:48.120 sunlight that feeds them. If you look at the history 0:04:48.160 --> 0:04:50.960 of earth life in the fossil record from roughly three 0:04:50.960 --> 0:04:54.479 and a half billion years ago until about one billion 0:04:54.560 --> 0:04:59.679 years ago, stramatallites absolutely dominate the scene, gathering in shallow 0:04:59.760 --> 0:05:03.400 sea ease and across continental shores around the world. But 0:05:03.480 --> 0:05:07.440 around a billion years ago, the finally layered stramatallites start 0:05:07.560 --> 0:05:11.160 to vanish from the geological record, and they've remained rare 0:05:11.279 --> 0:05:19.719 until today. What happened to them. There are several possibilities, 0:05:19.760 --> 0:05:23.159 but one interesting investigation into this question was a study 0:05:23.200 --> 0:05:26.520 published in in p N A S by Joan M. 0:05:26.560 --> 0:05:30.200 Bernhardt at All. This study picks up from the observation 0:05:30.279 --> 0:05:34.160 that at around the same time stramaatellites began to decline 0:05:34.200 --> 0:05:37.000 in the fossil record, they seem to be replaced with 0:05:37.040 --> 0:05:41.600 a different kind of microbial matt formation called a thrombo lighte. 0:05:42.320 --> 0:05:47.480 Whereas stramatolites are layered rocks, thrombo lights are clotted rocks 0:05:47.839 --> 0:05:51.760 with a microstructure to match their name. So did most 0:05:51.839 --> 0:05:57.039 of the world stromatallites become thrombo lights and if so why? 0:05:57.440 --> 0:06:00.400 The researchers behind this study suggest that thenswer to the 0:06:00.480 --> 0:06:04.080 question may lie in the evolution of another organism known 0:06:04.120 --> 0:06:09.280 as foraminifera. Foraminifera, often shortened to four ams, are a 0:06:09.360 --> 0:06:12.680 type of single celled eukaryotic organism from the Kingdom of 0:06:12.760 --> 0:06:16.599 life known as the protests. Along with organisms like amibas 0:06:16.720 --> 0:06:20.880 and the Plasmodium parasite that causes malaria. You can find 0:06:20.960 --> 0:06:24.920 for Aminifera throughout the ocean, often in seafloor sediments, where 0:06:24.960 --> 0:06:30.280 they use amazing and fantastically creepy, shape shifting tendrils called 0:06:30.440 --> 0:06:34.559 pseudopods to reach out into their surroundings and snatch up food. 0:06:35.440 --> 0:06:39.760 For Aminifera build tiny shells for themselves called tests, and 0:06:39.880 --> 0:06:43.080 they first evolved roughly around the time the stramatallites were 0:06:43.120 --> 0:06:47.080 declining and the thrombo lights began to rise, so it 0:06:47.200 --> 0:06:49.600 makes sense to wonder if they had something to do 0:06:49.839 --> 0:06:53.240 with the change in Earth's microbial lites. The authors of 0:06:54.160 --> 0:06:56.640 study wanted to see if the presence of for Aminifera 0:06:56.760 --> 0:06:59.880 in a living stormatellite would have a noticeable effect on 0:07:00.040 --> 0:07:04.200 how new mineral layers were accumulated, so they took modern 0:07:04.360 --> 0:07:07.440 living stormatellites from a place called high Born Key in 0:07:07.520 --> 0:07:11.800 the Bahamas and seeded them with foams. Some of the 0:07:11.880 --> 0:07:14.760 test samples were treated with a drug that would inhibit 0:07:14.880 --> 0:07:19.000 the function of the forum pseudopods, while others were left untreated. 0:07:19.640 --> 0:07:22.400 After about six months, they found that the presence of 0:07:22.520 --> 0:07:26.680 functional forums could absolutely affect the structure of the stormatallites. 0:07:27.320 --> 0:07:30.560 In samples where the foreams had been drugged, thin layers 0:07:30.600 --> 0:07:33.720 were visible. In the samples where the forearms were allowed 0:07:33.760 --> 0:07:37.000 to do their thing, the stramatallites had assumed the clotted 0:07:37.120 --> 0:07:41.600 structure seen today in thrombolites. Altogether, this is taken as 0:07:41.640 --> 0:07:43.760 evidence that the forum and if um may have had 0:07:43.840 --> 0:07:47.400 something to do with the stormatellites decline. Today, you can 0:07:47.480 --> 0:07:51.480 only find living stramatallites in special places, usually places with 0:07:51.640 --> 0:07:55.920 water that has a very high salinity, like evaporating salt 0:07:55.960 --> 0:07:59.680 water pools and tidal areas. I kept thinking about how 0:08:00.040 --> 0:08:03.600 in this way stramatollites have something in common with sauerkraut. 0:08:04.360 --> 0:08:08.240 Lacto fermented foods like sauerkraut and kimchi are made by 0:08:08.280 --> 0:08:12.520 salting vegetables and packing them down in a wet, anaerobic environment. 0:08:13.280 --> 0:08:16.320 The reason the vegetables turn nice and sour instead of 0:08:16.400 --> 0:08:19.680 simply rotting is that the salty wet conditions in the 0:08:19.800 --> 0:08:23.600 jar inhibit the growth of microbes and mold that cause spoilage, 0:08:23.960 --> 0:08:27.880 but allow the growth of salt tolerant lactic acid bacteria. 0:08:28.360 --> 0:08:31.720 As the lactic acid bacteria thrive, they produce acid as 0:08:31.760 --> 0:08:35.040 a byproduct of their metabolism, which lowers the pH of 0:08:35.080 --> 0:08:39.600 the fermentation, further preventing other microbes from surviving and creating 0:08:39.640 --> 0:08:44.360 the sour flavors we love. Wild stramatollites today tend to 0:08:44.440 --> 0:08:48.640 survive in high salinity environments where organisms that would otherwise 0:08:48.800 --> 0:08:52.160 graze on the exposed mats and eat them up just 0:08:52.320 --> 0:08:59.280 can't tolerate the salt. Tune into new editions of the 0:08:59.400 --> 0:09:03.720 artifact Free Wednesday, hosted either by Robert or myself. As always, 0:09:03.800 --> 0:09:06.720 you can email us at contact at stuff to Blow 0:09:06.800 --> 0:09:17.240 your Mind dot com. Stuff to Blow your Mind is 0:09:17.240 --> 0:09:19.880 a production of I Heart Radio. For more podcasts for 0:09:19.920 --> 0:09:22.960 my heart Radio, visit the i heart Radio app, Apple Podcasts, 0:09:23.040 --> 0:09:24.800 or wherever you listen to your favorite shows.