1 00:00:02,040 --> 00:00:07,160 Speaker 1: Welcome to brain Stuff from how Stuff Works, Hey, brain Stuff, 2 00:00:07,200 --> 00:00:10,480 Speaker 1: Lauren bog obam Here. Thanks to greenhouse gas emissions, the 3 00:00:10,480 --> 00:00:13,400 Speaker 1: percentage of carbon dioxide in our atmosphere is now equal 4 00:00:13,440 --> 00:00:16,360 Speaker 1: to about four hundred and twelve parts per million. That's 5 00:00:16,360 --> 00:00:19,239 Speaker 1: a sharp increase from what levels were even sixty years ago. 6 00:00:19,760 --> 00:00:23,480 Speaker 1: The World Meteorological Organization says Earth's atmosphere hasn't seen such 7 00:00:23,480 --> 00:00:25,720 Speaker 1: a high concentration of the gas in three to five 8 00:00:25,840 --> 00:00:29,640 Speaker 1: million years. Harmful emissions are just one of the environmental 9 00:00:29,680 --> 00:00:33,360 Speaker 1: concerns that today's leaders must confront. Trash accumulation is another. 10 00:00:33,800 --> 00:00:36,920 Speaker 1: Since the nineteen fifties, humans have generated about nine billion 11 00:00:37,000 --> 00:00:39,680 Speaker 1: tons that's eight point three metric tons of plastic and 12 00:00:39,760 --> 00:00:43,239 Speaker 1: dumped most of it in landfills. Plus Homo sapiens are 13 00:00:43,320 --> 00:00:47,120 Speaker 1: overpopulating like wild as our numbers skyrocket, loads of other 14 00:00:47,159 --> 00:00:50,080 Speaker 1: species find themselves on the decline. You and I are 15 00:00:50,120 --> 00:00:52,559 Speaker 1: now witnessing one of the biggest mass extinction events of 16 00:00:52,560 --> 00:00:58,000 Speaker 1: all time. Donald Prothero, a paleontologist and geologist, put it 17 00:00:58,040 --> 00:01:01,400 Speaker 1: this way. We are a geological force in and of ourselves. 18 00:01:02,680 --> 00:01:05,520 Speaker 1: Mankind's overall impact on planet Earth has been so dramatic 19 00:01:05,560 --> 00:01:08,199 Speaker 1: that some scientists then could change to the geologic time 20 00:01:08,240 --> 00:01:11,320 Speaker 1: scale is in order. According to them, we should reclassify 21 00:01:11,360 --> 00:01:13,600 Speaker 1: the very recent past as a new unit in time 22 00:01:14,000 --> 00:01:17,479 Speaker 1: defined by humanities long lasting marks on the world's climate, geology, 23 00:01:17,560 --> 00:01:21,480 Speaker 1: and biological makeup. This proposed unit has a name, the 24 00:01:21,560 --> 00:01:26,000 Speaker 1: anthropasy in epoch, meaning the age of humans. Earth is 25 00:01:26,040 --> 00:01:29,760 Speaker 1: about four point five four billion years old. Geologists have 26 00:01:29,800 --> 00:01:32,600 Speaker 1: split its history into large blocks of time called eons, 27 00:01:32,640 --> 00:01:36,160 Speaker 1: which are further subdivided into eras, those in turn are 28 00:01:36,160 --> 00:01:39,520 Speaker 1: made up of smaller units called periods. Finally, the divisions 29 00:01:39,520 --> 00:01:42,880 Speaker 1: within a period are known as epochs. So right now 30 00:01:43,080 --> 00:01:45,720 Speaker 1: we're living in the co ordinary period of the Cenozoic Era, 31 00:01:45,920 --> 00:01:48,720 Speaker 1: which is part of the Phanerozoic eon. But the question 32 00:01:48,800 --> 00:01:51,480 Speaker 1: is what's the current epoch. If you'd asked someone a 33 00:01:51,520 --> 00:01:54,840 Speaker 1: hundred years ago, that have said the Holocene Epoch. But 34 00:01:55,040 --> 00:01:58,680 Speaker 1: therein lies the debate. Earth's most recent ice age ended 35 00:01:58,720 --> 00:02:02,080 Speaker 1: eleven thousand seven years ago. That point in time is 36 00:02:02,120 --> 00:02:05,120 Speaker 1: recognized as the end of the Pleistocene epoch, which began 37 00:02:05,240 --> 00:02:07,600 Speaker 1: just less than two point six million years ago, and 38 00:02:07,640 --> 00:02:11,120 Speaker 1: the dawn of the Holocene Epoch. The dividing lines between 39 00:02:11,120 --> 00:02:14,360 Speaker 1: epox correspond with important moments in Earth's history, like abrupt 40 00:02:14,440 --> 00:02:17,440 Speaker 1: changes in the climate. Evidence for these events is typically 41 00:02:17,480 --> 00:02:20,400 Speaker 1: found within the layers or strata of rock on our planet. 42 00:02:20,680 --> 00:02:25,600 Speaker 1: Ice core samples may also contain clues. Persaro explained, nowadays, 43 00:02:25,680 --> 00:02:27,920 Speaker 1: epos are defined by a section of rock that has 44 00:02:28,000 --> 00:02:31,000 Speaker 1: distinctive boundaries at the top and bottom. He added that 45 00:02:31,080 --> 00:02:34,079 Speaker 1: specific epox are also sometimes characterized by the presence or 46 00:02:34,120 --> 00:02:37,800 Speaker 1: absence of key fossils, though note that larger changes, like 47 00:02:37,880 --> 00:02:40,800 Speaker 1: the mass extinction of the non avian dinosaurs, are marked 48 00:02:40,800 --> 00:02:44,320 Speaker 1: by changes in eras. Our Cenozoic era, for example, is 49 00:02:44,360 --> 00:02:47,960 Speaker 1: the age of mammals. The end of the Last Ice 50 00:02:48,000 --> 00:02:50,639 Speaker 1: Age marked the beginning of the Holocene and established its 51 00:02:50,639 --> 00:02:54,040 Speaker 1: lower boundary. It's traditionally been thought that this particular epoch 52 00:02:54,160 --> 00:02:57,480 Speaker 1: is still going on today, but in the year two thousand, 53 00:02:57,680 --> 00:03:02,280 Speaker 1: Nobel Laureate Paul Krutston helped popularize an alternative viewpoint. That year, 54 00:03:02,400 --> 00:03:05,800 Speaker 1: heat and biologist Eugene F. Stormer argued that recent human 55 00:03:05,840 --> 00:03:08,400 Speaker 1: activities had pushed the world out of the Holocene and 56 00:03:08,480 --> 00:03:11,720 Speaker 1: into a new epoch. Decades earlier, Stormer had coined the 57 00:03:11,840 --> 00:03:15,040 Speaker 1: term Anthropocene, derived from the Greek word for human, as 58 00:03:15,080 --> 00:03:18,360 Speaker 1: a possible name for this hypothetical new unit of geologic time, 59 00:03:19,080 --> 00:03:23,200 Speaker 1: It's stuck. The International Commission on Strategraphy is the body 60 00:03:23,240 --> 00:03:27,040 Speaker 1: that standardizes the geologic time scale. It has yet to 61 00:03:27,040 --> 00:03:30,560 Speaker 1: recognize the Anthropocene as an official epoch, although the topic 62 00:03:30,600 --> 00:03:33,720 Speaker 1: has been discussed. As of this writing, the Commission maintains 63 00:03:33,800 --> 00:03:37,800 Speaker 1: the Holocene is still ongoing, but maybe scientists will feel 64 00:03:37,800 --> 00:03:41,280 Speaker 1: differently someday. Pharos heard it argued that geologists living in 65 00:03:41,320 --> 00:03:43,520 Speaker 1: the far off future, perhaps even tens of millions of 66 00:03:43,600 --> 00:03:46,520 Speaker 1: years from now quote, could tell when humans were here 67 00:03:46,560 --> 00:03:49,080 Speaker 1: because we've left so many traces in the rocks. Chemical 68 00:03:49,120 --> 00:03:53,720 Speaker 1: traces as well as actual physical objects like trash. Seawater 69 00:03:53,760 --> 00:03:57,080 Speaker 1: absorbs about one fourth of our carbon dioxide emissions. This 70 00:03:57,120 --> 00:03:59,960 Speaker 1: has led to widespread ocean a certification which will doubt 71 00:04:00,040 --> 00:04:03,800 Speaker 1: us leave telltale limestones behind. Dissolved carbonates in the sediment 72 00:04:03,840 --> 00:04:05,720 Speaker 1: are going to be another one of our calling cards. 73 00:04:06,120 --> 00:04:09,160 Speaker 1: Future paleontologists may also notice the sudden disappearance of a 74 00:04:09,160 --> 00:04:13,080 Speaker 1: great many species from the fossil record. We would also expect, 75 00:04:13,120 --> 00:04:16,400 Speaker 1: as yet unborn researchers to discover the radiometric signatures of 76 00:04:16,440 --> 00:04:19,880 Speaker 1: nuclear weaponry all around the world. Plutonium two thirty nine, 77 00:04:19,920 --> 00:04:22,640 Speaker 1: which is uncommon in nature, was embedded in sediments that 78 00:04:22,720 --> 00:04:24,960 Speaker 1: lay exposed to the air during the nuclear tests of 79 00:04:24,960 --> 00:04:27,920 Speaker 1: the nineteen forties, and that brings us to a bone 80 00:04:27,920 --> 00:04:30,839 Speaker 1: of contention about the Anthropocene. If it really is a 81 00:04:30,920 --> 00:04:34,360 Speaker 1: legitimate geological epoch, what moment in history should we recognize 82 00:04:34,360 --> 00:04:38,000 Speaker 1: as its starting point. One argument is that the Anthropocene 83 00:04:38,000 --> 00:04:40,440 Speaker 1: began in the nineteen forties, when the first atomic weapon 84 00:04:40,480 --> 00:04:43,680 Speaker 1: detonations occurred, like the famous Trinity nuclear test of nine. 85 00:04:45,040 --> 00:04:47,680 Speaker 1: Another option might be to define the Anthropocene as everything 86 00:04:47,720 --> 00:04:51,920 Speaker 1: that's happened since the Industrial Revolution kicked off. Per thea said, 87 00:04:52,279 --> 00:04:54,440 Speaker 1: others have wanted to push the lower boundary date all 88 00:04:54,440 --> 00:04:57,080 Speaker 1: the way back to when humans really started transforming the planet, 89 00:04:57,080 --> 00:04:59,760 Speaker 1: at the beginning of civilization and agriculture, at least ten 90 00:04:59,839 --> 00:05:04,360 Speaker 1: or eleven thousand years ago. Regardless, if the geological community 91 00:05:04,360 --> 00:05:07,080 Speaker 1: ever officially splits up the Holocene and rebrands these past 92 00:05:07,080 --> 00:05:10,200 Speaker 1: few decades, century or millennia as the anthroposy, and a 93 00:05:10,200 --> 00:05:13,919 Speaker 1: potential benefit might be the gestures symbolic value. Kreston and 94 00:05:13,960 --> 00:05:16,080 Speaker 1: many others hope it would send a powerful message to 95 00:05:16,080 --> 00:05:19,760 Speaker 1: governments and private citizens alike. As Perso puts it, when 96 00:05:19,839 --> 00:05:22,920 Speaker 1: you use that term, everyone else then realizes the geologists 97 00:05:22,960 --> 00:05:25,200 Speaker 1: are making a statement about what we've done to the planet. 98 00:05:30,320 --> 00:05:32,760 Speaker 1: Today's episode was written by Mark Mancini and produced by 99 00:05:32,760 --> 00:05:35,400 Speaker 1: Tyler Clang for iHeart Media and How Stuff Works. If 100 00:05:35,400 --> 00:05:37,760 Speaker 1: this episode piqued your interest about where our world is going, 101 00:05:38,040 --> 00:05:40,279 Speaker 1: check out the podcast The End of the World Josh 102 00:05:40,279 --> 00:05:42,919 Speaker 1: Clark for more existential dread and what we can do 103 00:05:42,960 --> 00:05:45,320 Speaker 1: to help fix it, And of course, for more on 104 00:05:45,360 --> 00:05:47,600 Speaker 1: this and lots of other earth changing topics, visit our 105 00:05:47,640 --> 00:06:01,000 Speaker 1: home planet, how Stuff Works dot com.