Speaker 1: Welcome to brain Stuff from how Stuff Works, Hey, brain Stuff,
Speaker 1: Lauren bog obam Here. Thanks to greenhouse gas emissions, the
Speaker 1: percentage of carbon dioxide in our atmosphere is now equal
Speaker 1: to about four hundred and twelve parts per million. That's
Speaker 1: a sharp increase from what levels were even sixty years ago.
Speaker 1: The World Meteorological Organization says Earth's atmosphere hasn't seen such
Speaker 1: a high concentration of the gas in three to five
Speaker 1: million years. Harmful emissions are just one of the environmental
Speaker 1: concerns that today's leaders must confront. Trash accumulation is another.
Speaker 1: Since the nineteen fifties, humans have generated about nine billion
Speaker 1: tons that's eight point three metric tons of plastic and
Speaker 1: dumped most of it in landfills. Plus Homo sapiens are
Speaker 1: overpopulating like wild as our numbers skyrocket, loads of other
Speaker 1: species find themselves on the decline. You and I are
Speaker 1: now witnessing one of the biggest mass extinction events of
Speaker 1: all time. Donald Prothero, a paleontologist and geologist, put it
Speaker 1: this way. We are a geological force in and of ourselves.
Speaker 1: Mankind's overall impact on planet Earth has been so dramatic
Speaker 1: that some scientists then could change to the geologic time
Speaker 1: scale is in order. According to them, we should reclassify
Speaker 1: the very recent past as a new unit in time
Speaker 1: defined by humanities long lasting marks on the world's climate, geology,
Speaker 1: and biological makeup. This proposed unit has a name, the
Speaker 1: anthropasy in epoch, meaning the age of humans. Earth is
Speaker 1: about four point five four billion years old. Geologists have
Speaker 1: split its history into large blocks of time called eons,
Speaker 1: which are further subdivided into eras, those in turn are
Speaker 1: made up of smaller units called periods. Finally, the divisions
Speaker 1: within a period are known as epochs. So right now
Speaker 1: we're living in the co ordinary period of the Cenozoic Era,
Speaker 1: which is part of the Phanerozoic eon. But the question
Speaker 1: is what's the current epoch. If you'd asked someone a
Speaker 1: hundred years ago, that have said the Holocene Epoch. But
Speaker 1: therein lies the debate. Earth's most recent ice age ended
Speaker 1: eleven thousand seven years ago. That point in time is
Speaker 1: recognized as the end of the Pleistocene epoch, which began
Speaker 1: just less than two point six million years ago, and
Speaker 1: the dawn of the Holocene Epoch. The dividing lines between
Speaker 1: epox correspond with important moments in Earth's history, like abrupt
Speaker 1: changes in the climate. Evidence for these events is typically
Speaker 1: found within the layers or strata of rock on our planet.
Speaker 1: Ice core samples may also contain clues. Persaro explained, nowadays,
Speaker 1: epos are defined by a section of rock that has
Speaker 1: distinctive boundaries at the top and bottom. He added that
Speaker 1: specific epox are also sometimes characterized by the presence or
Speaker 1: absence of key fossils, though note that larger changes, like
Speaker 1: the mass extinction of the non avian dinosaurs, are marked
Speaker 1: by changes in eras. Our Cenozoic era, for example, is
Speaker 1: the age of mammals. The end of the Last Ice
Speaker 1: Age marked the beginning of the Holocene and established its
Speaker 1: lower boundary. It's traditionally been thought that this particular epoch
Speaker 1: is still going on today, but in the year two thousand,
Speaker 1: Nobel Laureate Paul Krutston helped popularize an alternative viewpoint. That year,
Speaker 1: heat and biologist Eugene F. Stormer argued that recent human
Speaker 1: activities had pushed the world out of the Holocene and
Speaker 1: into a new epoch. Decades earlier, Stormer had coined the
Speaker 1: term Anthropocene, derived from the Greek word for human, as
Speaker 1: a possible name for this hypothetical new unit of geologic time,
Speaker 1: It's stuck. The International Commission on Strategraphy is the body
Speaker 1: that standardizes the geologic time scale. It has yet to
Speaker 1: recognize the Anthropocene as an official epoch, although the topic
Speaker 1: has been discussed. As of this writing, the Commission maintains
Speaker 1: the Holocene is still ongoing, but maybe scientists will feel
Speaker 1: differently someday. Pharos heard it argued that geologists living in
Speaker 1: the far off future, perhaps even tens of millions of
Speaker 1: years from now quote, could tell when humans were here
Speaker 1: because we've left so many traces in the rocks. Chemical
Speaker 1: traces as well as actual physical objects like trash. Seawater
Speaker 1: absorbs about one fourth of our carbon dioxide emissions. This
Speaker 1: has led to widespread ocean a certification which will doubt
Speaker 1: us leave telltale limestones behind. Dissolved carbonates in the sediment
Speaker 1: are going to be another one of our calling cards.
Speaker 1: Future paleontologists may also notice the sudden disappearance of a
Speaker 1: great many species from the fossil record. We would also expect,
Speaker 1: as yet unborn researchers to discover the radiometric signatures of
Speaker 1: nuclear weaponry all around the world. Plutonium two thirty nine,
Speaker 1: which is uncommon in nature, was embedded in sediments that
Speaker 1: lay exposed to the air during the nuclear tests of
Speaker 1: the nineteen forties, and that brings us to a bone
Speaker 1: of contention about the Anthropocene. If it really is a
Speaker 1: legitimate geological epoch, what moment in history should we recognize
Speaker 1: as its starting point. One argument is that the Anthropocene
Speaker 1: began in the nineteen forties, when the first atomic weapon
Speaker 1: detonations occurred, like the famous Trinity nuclear test of nine.
Speaker 1: Another option might be to define the Anthropocene as everything
Speaker 1: that's happened since the Industrial Revolution kicked off. Per thea said,
Speaker 1: others have wanted to push the lower boundary date all
Speaker 1: the way back to when humans really started transforming the planet,
Speaker 1: at the beginning of civilization and agriculture, at least ten
Speaker 1: or eleven thousand years ago. Regardless, if the geological community
Speaker 1: ever officially splits up the Holocene and rebrands these past
Speaker 1: few decades, century or millennia as the anthroposy, and a
Speaker 1: potential benefit might be the gestures symbolic value. Kreston and
Speaker 1: many others hope it would send a powerful message to
Speaker 1: governments and private citizens alike. As Perso puts it, when
Speaker 1: you use that term, everyone else then realizes the geologists
Speaker 1: are making a statement about what we've done to the planet.
Speaker 1: Today's episode was written by Mark Mancini and produced by
Speaker 1: Tyler Clang for iHeart Media and How Stuff Works. If
Speaker 1: this episode piqued your interest about where our world is going,
Speaker 1: check out the podcast The End of the World Josh
Speaker 1: Clark for more existential dread and what we can do
Speaker 1: to help fix it, And of course, for more on
Speaker 1: this and lots of other earth changing topics, visit our
Speaker 1: home planet, how Stuff Works dot com.