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Join us on a thrilling journey as scientists reveal a terrifying new discovery hidden in the depths of Australia, while anthropologists uncover a stunning revelation about the mysterious Neanderthals.
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00:00So many asteroids pass through our solar system, and we don't even know about it.
00:05Those are rocky pieces of material left over from the time when our solar system was forming, about 4.6
00:12billion years ago.
00:13They move around the sun, but not in the way planets do.
00:17We're talking about true rebels that prefer to follow some pretty strange paths.
00:22Plus, they spin in different ways as they travel between planets and other space objects.
00:28And the majority of them come from the main asteroid belt that's located between Jupiter and Mars.
00:34Most stay there, but Jupiter has quite a strong gravity, so it can push some of those flying rocks in
00:41different directions, and towards us too.
00:44They're sometimes round, and sometimes they have odd shapes, with pits and holes from all that crashing into other space
00:51rocks.
00:52As we currently know, there are more than a million of them in the main asteroid belt.
00:57And that's all good, until some of them move in our direction.
01:02NASA keeps an eye on them, so we know everything's fine, at least for now.
01:06But that wasn't always the case with our beloved home planet.
01:09If Earth could talk, it would probably share so many crazy asteroid stories.
01:15We're talking about those space rocks that left impact craters we call domes.
01:20They have a specific shape with a raised center, similar to when you throw a pebble in a pond and
01:26see some water splashing upward.
01:29But we'll never be able to learn about many others.
01:32I know this raised center sounds like something you're supposed to see right away, especially if an asteroid that once
01:38slammed into the surface was big.
01:40But we're talking about millions and millions of years of erosion, so wind, water, and even gravity do what they
01:48do best and erase traces.
01:51They wear down impact domes, and some sites even end up hidden under layers of rock and dirt.
01:57Or they disappear forever, because Earth's tectonic plates keep moving around.
02:01Check out the Moon. It's experienced many collisions, too.
02:06But over there, there's no ocean or tectonic plates moving around, or even wind to slowly, through millions of years,
02:13erase craters from its face.
02:16Basically, its entire history is written on its surface.
02:19But Earth has its own forces that can erase such places as the Vetterfort impact structure and the Chicxulub crater.
02:26You know, the famous one that wiped out the dinosaurs?
02:29Luckily, scientists have new methods to find ancient craters.
02:33They often focus on the mess impacts made, which means the materials they threw around.
02:39And the Australian continent is especially interesting, since we're talking about a playground for asteroid hits.
02:46By that, I mean ancient supercontinent Gondwana that dominated the South hundreds of millions of years ago.
02:54Experts know about 38 impacts, plus they speculate about 43 more.
02:59Some structures are relatively small, while others are big and completely hidden.
03:04And recently, a scientist named Tony Yates has discovered strange underground magnetic patterns in New South Wales, Australia.
03:12Yay! New clues of a giant asteroid impact!
03:15And when I say giant, I really mean it.
03:18It's a structure 323 miles in diameter.
03:23This might be the largest impact site ever found.
03:27This spot is called the deniliquin structure.
03:30Its magnetic patterns show characteristic ripples around the center, like when a rock hits the water.
03:36There are also fractures that go outward from the center.
03:39And it seems rocks from inside Earth ended up pushed into these fractures.
03:45That's a typical story for big asteroid impacts.
03:49This structure was probably located in eastern Gondwana hundreds of millions of years ago,
03:55way before it split into several continents, including Australia.
03:59At the moment, all we know about this crater is what we see on the surface.
04:03To find more information about this collision and get some proof,
04:06we'll have to drill into the ground.
04:09An asteroid this big is definitely not a joke.
04:13It could have caused a massive ice age and maybe even wiped out around 85% of species,
04:19even more than the asteroid that ended dinosaurs.
04:23In 4.5 billion years, which is how long our planet has existed,
04:27it's been punched by hundreds of big asteroids.
04:30But that doesn't mean every space rock that enters our atmosphere
04:33really makes it all the way to the ground.
04:35Most of those that manage to pass the atmosphere are relatively small,
04:40for instance, 3 feet across.
04:42That's good for us because any space rock that's less than 82 feet in diameter
04:47most likely won't make it past our planet's atmosphere.
04:51Since these space rocks come towards us very fast,
04:55they heat up the gases in the atmosphere, which burns them away.
04:58By the way, once cosmic intruders enter our atmosphere,
05:02they turn into meteors.
05:04And in most cases, they don't cause much damage, if any, as they fall down.
05:09But we used to have way larger things flying around and crashing into Earth.
05:14At least 190 of them have left scars you can still see today.
05:19One of the really, really big ones is in South Africa.
05:22It's 99 miles wide.
05:25It's actually the largest.
05:26At least that's what scientists think at the moment
05:29because they still need to check as many details as possible
05:32about this new crater in Australia.
05:34This one in South Africa formed about 2 billion years ago,
05:38and an asteroid that created it was probably larger
05:41than the one that had wiped dinosaurs away.
05:44And when an asteroid is bigger than 0.6 miles,
05:48it can have really big effects across the world.
05:51This impact was so strong that it could have caused fires everywhere
05:56and thrown lots of dust into the air.
05:58And when you have so much dust in the atmosphere,
06:00the climate on the planet can change for months or even years.
06:05Then we also have the most popular asteroid
06:08that made a giant hole we today call the Chicxulub Crater.
06:12You know the story.
06:13It crashed into our planet 66 million years ago
06:16when dinosaurs were wandering around,
06:19catching food, falling in love,
06:21basically just doing their thing.
06:23The crash itself didn't erase them right away.
06:26It threw a lot of debris into space.
06:28And when it fell back to Earth, fires and flames were everywhere.
06:32The hit also produced a big cloud of dust
06:35that covered the planet for years.
06:37This cloud blocked the sunlight,
06:39which harmed plants and entire food chains.
06:41Even those dinosaurs that survived the crash
06:44and such difficult conditions had a hard time finding food.
06:47So they didn't make it.
06:49At least they left us many fossils
06:51and turned into the inspiration for movies and stories.
06:55A long time ago in Canada,
06:57something big crashed into our planet
06:59and left a big hole we today know as the Sudbury Basin.
07:03People used to think it was an asteroid,
07:05but now some experts think it might have been a giant comet
07:09made up of a mix of ice and rocks.
07:11The hole is almost gone now
07:13because of weather conditions though.
07:15But people still get to mine iron and nickel there
07:18and at the same time,
07:19find the leftovers of whatever space object fell there.
07:23If you move deep in southern India,
07:26you'll find a big hole called Loner Crater.
07:29Locals stumbled upon it 200 years ago
07:31and believed it might be from a volcano.
07:34But now we know it's a trace from a meteor
07:37that crashed into the ground about 35 to 50,000 years ago.
07:42What's so special about this crater
07:44is that it's the only one known
07:46to have formed in a type of rock called basalt.
07:48Around the crater,
07:50there are hills covered in trees
07:51and animals like peafowls and gazelles live there.
07:54Birds also like to visit the lake
07:56near the crater during the winter.
07:58And the lake itself is quite interesting too.
08:01It can turn pink
08:02because of all those tiny organisms that live there.
08:05But this color change doesn't last long.
08:11You're way more Neanderthal than you think,
08:14at least when it comes to your DNA.
08:16These ancient hominids were shorter
08:19and stockier than humans today.
08:21They made stone tools,
08:23used fire,
08:24wore clothing,
08:25and had some rituals of their own.
08:27The official theory says
08:29that they went extinct 40,000 years ago.
08:32But a new study says
08:33Neanderthals probably never really disappeared completely,
08:36but could have mixed with modern humans.
08:39It looks like every modern human
08:41has about 3% of the Neanderthal genome in their DNA.
08:45If it's accurate,
08:47it means Neanderthals were more connected
08:48with our ancestors than we previously thought
08:51and shared a long history of living together.
08:55Neanderthals were very close relatives of modern humans.
08:59But our families separated
09:01about half a million years ago.
09:03More than 10 years ago,
09:04scientists discovered that Neanderthals
09:07had families with the early humans
09:08who traveled out of Africa.
09:10Because of this,
09:12people living outside of Africa today
09:14have about 1-2% of Neanderthal DNA in their genes.
09:18We now have only 3 really good examples
09:21of complete genetic code
09:22from these ancient hominids.
09:24The first one comes from bones
09:26found in a cave in Croatia
09:28that are 50,000 to 65,000 years old.
09:31Two more examples,
09:33which are about 80,000 and 50,000 years old,
09:36were found in caves in Eurasia.
09:39Scientists still aren't sure as much
09:41about how modern human DNA
09:43got into the Neanderthal genetic alphabet
09:46because they don't have enough material to study.
09:48But they did compare the existing DNA
09:50of 3 Neanderthals
09:52with the DNA of 2,000 modern humans.
09:55They found that the Neanderthal DNA
09:57might be made up of up to 3.7%
10:00of modern human genetic code.
10:03It means that in the ancient Neanderthal population,
10:06about 1 in 30 parents were modern humans.
10:10The scientists found that modern human DNA
10:13got mixed into the Neanderthal genetic alphabet
10:15during at least two periods
10:17when humans and Neanderthals were interbreeding.
10:20This happened once
10:22about 200,000 to 250,000 years ago
10:25and again about 100,000 to 120,000 years ago.
10:30There might have been other times they mixed,
10:32but we can't see those in the DNA we have now.
10:36Another recent study,
10:37which hasn't been fully checked
10:38by other scientists yet,
10:40says that most of the Neanderthal DNA
10:42in modern humans
10:43came from one big period of mixing
10:46about 47,000 years ago
10:48that lasted for almost 7,000 years.
10:51Scientists found skulls
10:53that are about 100,000 years old
10:55in two caves in the Middle East.
10:57These skulls look like they belonged
10:59to early modern humans,
11:01but have some features like bigger eyebrows
11:03that might show they had Neanderthal DNA.
11:07This could be because of gene flow
11:09from Neanderthals,
11:10and it fits in the mixing time frame.
11:14The study also looked at the genetic differences
11:17in the three Neanderthal genomes
11:19and found out that Neanderthals
11:21had an even smaller population
11:23than scientists thought before.
11:25It could be another proof
11:27that Neanderthals didn't just go extinct,
11:29but became part of the modern human gene pool.
11:33Many groups of modern humans left Africa
11:36and mixed with Neanderthals
11:37so much that Neanderthals
11:39couldn't stay separate.
11:40In the future,
11:42scientists want to study
11:43how modern human DNA
11:44affected Neanderthals.
11:46This could help us understand
11:48if this mixing had good
11:49or bad effects on Neanderthals.
11:53Neanderthals aren't our only relatives
11:55from the past.
11:56There used to be at least
11:57nine species of humans on our planet.
12:00One of them, Homo habilis,
12:02earned the nickname Handyman
12:04because stone tools
12:06were found with its remains.
12:07It lived in eastern and southern Africa.
12:11This early human
12:12had a slightly larger brain
12:14than its older relatives
12:15and an ape-like face.
12:17Homo habilis was about four feet tall
12:19and ate a variety of foods.
12:22For a long time,
12:24scientists thought Homo habilis
12:25was the oldest member
12:26of our human family.
12:28But new dating methods
12:29have shown that Homo erectus,
12:32another ancient human,
12:33might be older
12:34and not related to Homo habilis.
12:37Homo naledi
12:38is a more mysterious member
12:40of our human family
12:41discovered in a South African cave
12:43in 2013.
12:45It's the only region of the world
12:47where their remains were found.
12:49They walked on two feet
12:50but were also good
12:51at climbing trees.
12:53They were small,
12:54about four feet nine inches tall,
12:57weighed around 88 pounds,
12:58and had small brains.
13:00We don't know much about
13:02how they lived
13:02since we haven't found
13:04stone tools
13:04or other cultural evidence.
13:06But some scientists think
13:08they might have buried
13:09their deceased
13:10and made cave art.
13:12In 2010,
13:14scientists found some fossils
13:16in a cave in Siberia,
13:17but they weren't sure
13:18what species they belonged to.
13:21These fossils are from a group
13:22called the Denisovans,
13:24who lived between 194,000
13:27and 51,000 years ago.
13:29We don't know much about them
13:31because we only have
13:32a few fossils.
13:33But DNA analysis
13:35has shown that Denisovans
13:37were closely related
13:38to Neanderthals
13:39and modern humans.
13:40They even had families
13:42with early humans,
13:43especially in Southeast Asia.
13:45There aren't enough fossils
13:47to give Denisovans
13:48their own species name,
13:49but their genes are found
13:51in modern humans,
13:52which means they might be part
13:54of our own species.
13:56As scientists study more
13:58about Denisovans
13:59and fossils in Southeast Asia,
14:01we might understand better
14:02how different species
14:04fit into the Homo family tree.
14:06In 2003,
14:08they found fossils
14:09of a very small human-like species
14:11in a cave
14:11on the island of Flores
14:13in Indonesia.
14:14These tiny people
14:15lived between 100,000
14:17and 50,000 years ago.
14:19They were only about
14:203 feet 6 inches tall.
14:23Scientists think
14:23they might have come
14:24from another species,
14:26Homo erectus,
14:27and became smaller over time
14:28because they lived
14:29on an island
14:30with limited food.
14:31Because of their small size,
14:33they're often nicknamed
14:34hobbits.
14:37Around 40,000 years ago,
14:39Homo sapiens,
14:40yep, that's us,
14:42were the last humans
14:43left out
14:44of many different kinds
14:45of human-like species
14:46that walked on two legs.
14:48So,
14:49the logical question is,
14:51what happened to the others?
14:52And what did we have to do
14:53with their disappearance?
14:55Some scientists think
14:56we survived
14:57because our offspring
14:58lived longer
14:59or because we were better
15:00at handling changes
15:01in the weather.
15:02Others think
15:03we might have competed
15:04with other human species
15:06or maybe mixed with them
15:07and shared genes.
15:10About 300,000 years ago,
15:13the first Homo sapiens
15:14lived in Africa.
15:15They didn't look exactly like us,
15:17but they were more similar to us
15:19than other early humans.
15:20They had tall, round skulls
15:22with almost straight foreheads.
15:24Unlike Neanderthals,
15:26they didn't have thick brows
15:27or jutting jaws
15:28like Homo naledi.
15:29They also had chins,
15:31which no other early humans had,
15:34though we still don't know why.
15:36Homo sapiens lived
15:37in bigger groups
15:38and had more genetic diversity
15:40compared to other early humans.
15:42This helped us in many ways,
15:44not just in staying healthy.
15:46Having big social networks
15:48across different places
15:49was like having a safety net.
15:51If we ran out of food or water,
15:54we could go to other groups
15:55we were connected to,
15:56and they would help us
15:57because we weren't strangers.
15:59We were family.
16:00These big networks
16:02also helped these early humans
16:03share new ideas
16:04and inventions.
16:06A big simulation
16:07showed that later species
16:09of humans
16:10could live in many
16:11different environments
16:12because of these wide networks
16:14and the ability to adapt.
16:15We know that Neanderthals
16:17were really smart,
16:18but Homo sapiens
16:19might have been
16:20just a little bit smarter.
16:22Small inventions
16:23like weaving and sewing needles
16:25could have given
16:26Homo sapiens an edge.
16:28Scientists have found evidence
16:29of weaving
16:29from 35,000 years ago
16:31and sewing needles
16:32from 30,000 years ago.
16:35Weaving lets you make things
16:36like baskets and nets
16:37to catch food.
16:39Sewing needles
16:39help you make better clothes
16:41and tents
16:41which keep you
16:43and your youngsters
16:44warm and safe
16:44which is very important
16:46for survival.
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