1 00:00:03,279 --> 00:00:05,640 Speaker 1: Welcome to Stuff to Blow Your Mind, a production of 2 00:00:05,640 --> 00:00:11,080 Speaker 1: I heeart Radio. Hi. My name is Joe McCormick, and 3 00:00:11,200 --> 00:00:14,640 Speaker 1: this is the Artifact, a short form series from Stuff 4 00:00:14,680 --> 00:00:18,560 Speaker 1: to Blow Your Mind, focusing on particular objects, ideas, and 5 00:00:18,680 --> 00:00:24,200 Speaker 1: moments in time. On the western coast of Australia, there's 6 00:00:24,239 --> 00:00:28,040 Speaker 1: a place called Shark Bay, and within Shark Bay there's 7 00:00:28,080 --> 00:00:32,120 Speaker 1: a nature reserve known as Hamlin Pool. Today you can 8 00:00:32,159 --> 00:00:34,920 Speaker 1: walk out over a wooden jetty at Hamlin Pool to 9 00:00:34,960 --> 00:00:39,680 Speaker 1: see the shallows up close. Down below, there are hundreds 10 00:00:39,720 --> 00:00:44,520 Speaker 1: of strange, bulbous mineral formations peeking up over the water 11 00:00:44,640 --> 00:00:47,840 Speaker 1: line or sitting just below it. It's hard to describe 12 00:00:47,840 --> 00:00:52,680 Speaker 1: exactly what they look like. Black stone broccoli perched upright 13 00:00:52,720 --> 00:00:57,200 Speaker 1: in the still water, atomic mushroom clouds frozen in place, 14 00:00:57,920 --> 00:01:01,560 Speaker 1: or dark pebbly brains flocking out of the Indian Ocean. 15 00:01:02,920 --> 00:01:06,640 Speaker 1: These are stromatolites. If you stand on the jetty at 16 00:01:06,640 --> 00:01:10,039 Speaker 1: Hamlin Pool looking out at this army of mineral bulbs, 17 00:01:10,440 --> 00:01:14,480 Speaker 1: you're getting a pretty close approximation of what most visible 18 00:01:14,560 --> 00:01:18,160 Speaker 1: life on planet Earth looked like for something like eighty 19 00:01:18,280 --> 00:01:22,679 Speaker 1: percent of its history. Because while these are mineral formations, 20 00:01:22,720 --> 00:01:28,440 Speaker 1: They're not just dead rock, they're alive and growing. Stromatolites 21 00:01:28,480 --> 00:01:32,840 Speaker 1: are one type from a class of mineral formations called microbiolites, 22 00:01:33,480 --> 00:01:38,080 Speaker 1: natural stone monuments that are built by microscopic organisms, and 23 00:01:38,160 --> 00:01:40,800 Speaker 1: not all of them look like the columns of mushroom 24 00:01:40,920 --> 00:01:45,880 Speaker 1: brain broccoli at Hamlin Bay. Some microbiolites are flat, some 25 00:01:46,000 --> 00:01:50,040 Speaker 1: are domed, and some form ascending pillars with different shapes 26 00:01:50,040 --> 00:01:54,000 Speaker 1: and contours. Though there are lots of microbiolites in the world, 27 00:01:54,080 --> 00:01:56,960 Speaker 1: there are only a handful of places left where you 28 00:01:56,960 --> 00:02:01,960 Speaker 1: can find true marine stromatolites growing in the wild. So 29 00:02:02,080 --> 00:02:07,320 Speaker 1: what makes us stromatallite special. The word stromatallite means layered rock. 30 00:02:08,000 --> 00:02:10,160 Speaker 1: If you look at a cross section, you can see 31 00:02:10,240 --> 00:02:15,480 Speaker 1: banded strata within them extremely thin layers of mineral deposition, 32 00:02:15,960 --> 00:02:19,280 Speaker 1: kind of like a stone puff pastry, with the layers 33 00:02:19,320 --> 00:02:23,840 Speaker 1: sometimes alternating between light and dark. And these layers actually 34 00:02:23,880 --> 00:02:27,760 Speaker 1: tell us something about the process that created them. Stromatallites 35 00:02:27,800 --> 00:02:33,280 Speaker 1: are built by microscopic organisms like photosynthetic cyanobacteria also known 36 00:02:33,320 --> 00:02:37,600 Speaker 1: as blue green algae. These are single celled life forms 37 00:02:37,639 --> 00:02:40,720 Speaker 1: that can be found almost everywhere on Earth, especially in 38 00:02:40,760 --> 00:02:46,000 Speaker 1: the water. Cyanobacteria like plants, survived by using energy from 39 00:02:46,040 --> 00:02:50,640 Speaker 1: the sunlight to convert carbon dioxide from the environment into food. 40 00:02:51,280 --> 00:02:55,400 Speaker 1: Though cyanobacteria existed for billions of years before the first 41 00:02:55,440 --> 00:02:59,120 Speaker 1: plants evolved, without them, you never would have been born. 42 00:02:59,840 --> 00:03:05,600 Speaker 1: As Earth's first photosynthesizers, microbes like cyanobacteria converted the planet's 43 00:03:05,600 --> 00:03:09,320 Speaker 1: early atmosphere into what it is today by polluting it 44 00:03:09,360 --> 00:03:13,840 Speaker 1: with their metabolic waste product, which is oxygen. Every animal 45 00:03:13,919 --> 00:03:17,320 Speaker 1: that ever lived could only evolve because of what the 46 00:03:17,360 --> 00:03:23,520 Speaker 1: early photosynthesizers did to the atmosphere. So for billions of years, 47 00:03:23,560 --> 00:03:27,760 Speaker 1: these microbes dominated planet Earth, changing the composition of the 48 00:03:27,800 --> 00:03:31,920 Speaker 1: air and leaving behind their stromatolite mineral formations in the 49 00:03:31,960 --> 00:03:35,240 Speaker 1: fossil record. But to come back to the question about 50 00:03:35,240 --> 00:03:38,560 Speaker 1: how they form, where do these layers of strata and 51 00:03:38,600 --> 00:03:42,920 Speaker 1: the stromatalite come from. Microbes like cyanobacteria don't just float 52 00:03:42,960 --> 00:03:46,880 Speaker 1: around by themselves. When they're able, they glom onto other 53 00:03:46,960 --> 00:03:50,480 Speaker 1: micro organisms to form what are known as biofilms or 54 00:03:50,600 --> 00:03:54,880 Speaker 1: microbial mats. Think of a kind of thin, sticky carpet 55 00:03:54,960 --> 00:03:58,760 Speaker 1: in which billions of microbes glue themselves both to one 56 00:03:58,760 --> 00:04:02,240 Speaker 1: another and to an underlying surface with the help of 57 00:04:02,280 --> 00:04:07,280 Speaker 1: a class of biological cement known as extracellular polymeric substances 58 00:04:07,360 --> 00:04:11,240 Speaker 1: or e p s s. These microbial mats, being sticky 59 00:04:11,320 --> 00:04:15,120 Speaker 1: by evolutionary design, don't just stick to the underlying substrate. 60 00:04:15,520 --> 00:04:18,520 Speaker 1: They also act kind of like a glue trap, catching 61 00:04:18,600 --> 00:04:22,159 Speaker 1: hold of tiny grains of sediment and sand that wash 62 00:04:22,240 --> 00:04:24,880 Speaker 1: over the surface of the mat due to the tide 63 00:04:25,000 --> 00:04:29,239 Speaker 1: or other mechanical forces. Over the years, layer by layer, 64 00:04:29,800 --> 00:04:33,960 Speaker 1: these sticky mats of biological material trapped sediment and also 65 00:04:34,080 --> 00:04:38,960 Speaker 1: calcium carbonate harden into solid mineral formations like the columns 66 00:04:39,000 --> 00:04:42,400 Speaker 1: at Shark Bay, always climbing up higher like the crown 67 00:04:42,440 --> 00:04:45,080 Speaker 1: of a tree in the forest, to move towards the 68 00:04:45,120 --> 00:04:48,120 Speaker 1: sunlight that feeds them. If you look at the history 69 00:04:48,160 --> 00:04:50,960 Speaker 1: of earth life in the fossil record from roughly three 70 00:04:50,960 --> 00:04:54,479 Speaker 1: and a half billion years ago until about one billion 71 00:04:54,560 --> 00:04:59,679 Speaker 1: years ago, stramatallites absolutely dominate the scene, gathering in shallow 72 00:04:59,760 --> 00:05:03,400 Speaker 1: sea ease and across continental shores around the world. But 73 00:05:03,480 --> 00:05:07,440 Speaker 1: around a billion years ago, the finally layered stramatallites start 74 00:05:07,560 --> 00:05:11,160 Speaker 1: to vanish from the geological record, and they've remained rare 75 00:05:11,279 --> 00:05:19,719 Speaker 1: until today. What happened to them. There are several possibilities, 76 00:05:19,760 --> 00:05:23,159 Speaker 1: but one interesting investigation into this question was a study 77 00:05:23,200 --> 00:05:26,520 Speaker 1: published in in p N A S by Joan M. 78 00:05:26,560 --> 00:05:30,200 Speaker 1: Bernhardt at All. This study picks up from the observation 79 00:05:30,279 --> 00:05:34,160 Speaker 1: that at around the same time stramaatellites began to decline 80 00:05:34,200 --> 00:05:37,000 Speaker 1: in the fossil record, they seem to be replaced with 81 00:05:37,040 --> 00:05:41,600 Speaker 1: a different kind of microbial matt formation called a thrombo lighte. 82 00:05:42,320 --> 00:05:47,480 Speaker 1: Whereas stramatolites are layered rocks, thrombo lights are clotted rocks 83 00:05:47,839 --> 00:05:51,760 Speaker 1: with a microstructure to match their name. So did most 84 00:05:51,839 --> 00:05:57,039 Speaker 1: of the world stromatallites become thrombo lights and if so why? 85 00:05:57,440 --> 00:06:00,400 Speaker 1: The researchers behind this study suggest that thenswer to the 86 00:06:00,480 --> 00:06:04,080 Speaker 1: question may lie in the evolution of another organism known 87 00:06:04,120 --> 00:06:09,280 Speaker 1: as foraminifera. Foraminifera, often shortened to four ams, are a 88 00:06:09,360 --> 00:06:12,680 Speaker 1: type of single celled eukaryotic organism from the Kingdom of 89 00:06:12,760 --> 00:06:16,599 Speaker 1: life known as the protests. Along with organisms like amibas 90 00:06:16,720 --> 00:06:20,880 Speaker 1: and the Plasmodium parasite that causes malaria. You can find 91 00:06:20,960 --> 00:06:24,920 Speaker 1: for Aminifera throughout the ocean, often in seafloor sediments, where 92 00:06:24,960 --> 00:06:30,280 Speaker 1: they use amazing and fantastically creepy, shape shifting tendrils called 93 00:06:30,440 --> 00:06:34,559 Speaker 1: pseudopods to reach out into their surroundings and snatch up food. 94 00:06:35,440 --> 00:06:39,760 Speaker 1: For Aminifera build tiny shells for themselves called tests, and 95 00:06:39,880 --> 00:06:43,080 Speaker 1: they first evolved roughly around the time the stramatallites were 96 00:06:43,120 --> 00:06:47,080 Speaker 1: declining and the thrombo lights began to rise, so it 97 00:06:47,200 --> 00:06:49,600 Speaker 1: makes sense to wonder if they had something to do 98 00:06:49,839 --> 00:06:53,240 Speaker 1: with the change in Earth's microbial lites. The authors of 99 00:06:54,160 --> 00:06:56,640 Speaker 1: study wanted to see if the presence of for Aminifera 100 00:06:56,760 --> 00:06:59,880 Speaker 1: in a living stormatellite would have a noticeable effect on 101 00:07:00,040 --> 00:07:04,200 Speaker 1: how new mineral layers were accumulated, so they took modern 102 00:07:04,360 --> 00:07:07,440 Speaker 1: living stormatellites from a place called high Born Key in 103 00:07:07,520 --> 00:07:11,800 Speaker 1: the Bahamas and seeded them with foams. Some of the 104 00:07:11,880 --> 00:07:14,760 Speaker 1: test samples were treated with a drug that would inhibit 105 00:07:14,880 --> 00:07:19,000 Speaker 1: the function of the forum pseudopods, while others were left untreated. 106 00:07:19,640 --> 00:07:22,400 Speaker 1: After about six months, they found that the presence of 107 00:07:22,520 --> 00:07:26,680 Speaker 1: functional forums could absolutely affect the structure of the stormatallites. 108 00:07:27,320 --> 00:07:30,560 Speaker 1: In samples where the foreams had been drugged, thin layers 109 00:07:30,600 --> 00:07:33,720 Speaker 1: were visible. In the samples where the forearms were allowed 110 00:07:33,760 --> 00:07:37,000 Speaker 1: to do their thing, the stramatallites had assumed the clotted 111 00:07:37,120 --> 00:07:41,600 Speaker 1: structure seen today in thrombolites. Altogether, this is taken as 112 00:07:41,640 --> 00:07:43,760 Speaker 1: evidence that the forum and if um may have had 113 00:07:43,840 --> 00:07:47,400 Speaker 1: something to do with the stormatellites decline. Today, you can 114 00:07:47,480 --> 00:07:51,480 Speaker 1: only find living stramatallites in special places, usually places with 115 00:07:51,640 --> 00:07:55,920 Speaker 1: water that has a very high salinity, like evaporating salt 116 00:07:55,960 --> 00:07:59,680 Speaker 1: water pools and tidal areas. I kept thinking about how 117 00:08:00,040 --> 00:08:03,600 Speaker 1: in this way stramatollites have something in common with sauerkraut. 118 00:08:04,360 --> 00:08:08,240 Speaker 1: Lacto fermented foods like sauerkraut and kimchi are made by 119 00:08:08,280 --> 00:08:12,520 Speaker 1: salting vegetables and packing them down in a wet, anaerobic environment. 120 00:08:13,280 --> 00:08:16,320 Speaker 1: The reason the vegetables turn nice and sour instead of 121 00:08:16,400 --> 00:08:19,680 Speaker 1: simply rotting is that the salty wet conditions in the 122 00:08:19,800 --> 00:08:23,600 Speaker 1: jar inhibit the growth of microbes and mold that cause spoilage, 123 00:08:23,960 --> 00:08:27,880 Speaker 1: but allow the growth of salt tolerant lactic acid bacteria. 124 00:08:28,360 --> 00:08:31,720 Speaker 1: As the lactic acid bacteria thrive, they produce acid as 125 00:08:31,760 --> 00:08:35,040 Speaker 1: a byproduct of their metabolism, which lowers the pH of 126 00:08:35,080 --> 00:08:39,600 Speaker 1: the fermentation, further preventing other microbes from surviving and creating 127 00:08:39,640 --> 00:08:44,360 Speaker 1: the sour flavors we love. Wild stramatollites today tend to 128 00:08:44,440 --> 00:08:48,640 Speaker 1: survive in high salinity environments where organisms that would otherwise 129 00:08:48,800 --> 00:08:52,160 Speaker 1: graze on the exposed mats and eat them up just 130 00:08:52,320 --> 00:08:59,280 Speaker 1: can't tolerate the salt. Tune into new editions of the 131 00:08:59,400 --> 00:09:03,720 Speaker 1: artifact Free Wednesday, hosted either by Robert or myself. As always, 132 00:09:03,800 --> 00:09:06,720 Speaker 1: you can email us at contact at stuff to Blow 133 00:09:06,800 --> 00:09:17,240 Speaker 1: your Mind dot com. Stuff to Blow your Mind is 134 00:09:17,240 --> 00:09:19,880 Speaker 1: a production of I Heart Radio. For more podcasts for 135 00:09:19,920 --> 00:09:22,960 Speaker 1: my heart Radio, visit the i heart Radio app, Apple Podcasts, 136 00:09:23,040 --> 00:09:24,800 Speaker 1: or wherever you listen to your favorite shows.