Life on Earth. Scientists have been studying it for centuries,
creating a timeline from when the first single-cell beings emerged in primordial waters to today
when billions of humans populate the surface. But there’s one question they’ve never
been able to answer with 100% certainty - how exactly did it begin? Most scientists think it started from a complex
chemical reaction in the water of the early Earth. Some argue for a more intelligent hand guiding
the process. The only thing that’s sure is that no one’s
sure - and everyone has an opinion. But what if the origin of life on Earth didn’t
actually come from Earth? Could life on earth be the product of extraterrestrials? So far, we don’t have any conclusive proof
for or against life outside of Earth. No contact has been made, and no DNA or fossils
from other lifeforms has been discovered. But we’ve only explored a tiny fragment
of the universe out there - almost none of it in person - and the odds that countless
planets surrounding countless stars would have no other planets capable of supporting
life since the Big Bang is pretty slim. And after billions of years of this universe
existing, many of those worlds may not exist anymore. Asteroids, comets, and other interstellar
phenomena can immediately bring a crushing end to any world’s lifeforms - as the dinosaurs
found out the hard way. But what if the life from those worlds...didn’t
stay on those worlds? The hypothesis is panspermia, which claims
that not only does life exist throughout the universe, but that it gets carried from world
to world by traveling objects like asteroids and comets. The space dust that gets attached to anything
traveling through space - even the spaceships that humans send to explore the moon and nearby
planets - may have microscopic forms of life in them that travel to other worlds and seed
them when they land, creating the building blocks of future life on those worlds. But could anything survive in the cold vacuum
of space? Well, we couldn’t, and neither could most
animals on Earth. But when you look at smaller animals, some
survive climates that could kill humans in seconds. The Pompeii Worm lives deep in hydrothermal
vents that can reach up to 175 degrees fahrenheit. The Flat Bark Beetle, which lives in some
of the coldest climates of North America, produces natural antifreeze chemicals that
help it survive the winter and enter into a sort of stasis - smoothly surviving the
coldest parts of the winter while we’re fighting over the thermostat. Neither of them could survive space - but
that’s not the case for one microscopic creature. The name “Water Bear” probably creates
cute images of an ursine mammal enjoying a bath in the river. But the real thing is much less cuddly - and
also less likely to eat you. Also called a Tardigrade, this tiny organism
is the only form of life that seems to be able to live anywhere, even in the most extreme
conditions. They’ve been found everywhere from deserts
to hot springs, and they may even potentially exist in space - thanks to a crash of a sample
from a spaceship on the moon. These tiny multi-legged creatures can dry
up and fall into a state that resembles death, but when exposed to water even decades later,
they spring back to life. So if life originated from outside Earth,
how exactly did it get here? There are a couple of theories of exactly
how those building blocks of life arrived on our ancient planet, most of them based
around interstellar physics. One theory from a Swedish scientist in 1903
theorizes that the radiation pressure from stars can send particles through space, but
this would only work for the smallest particles and many if not all would be killed off by
the radiation. But it’s possible that alien bacteria or
viruses could survive if shielded from UV radiation. The other main theory is that the particles
that led to the creation of life were hitchhikers on rocks, coming into contact with Earth when
the rocks crash-landed here. While we know how asteroids, comets, and meteors
travel through the galaxy, this is under far more extreme conditions than any lifeform
has been known to survive - surviving in the vacuum of space for years on end before crash-landing. But there is another theory - that the alien
lifeforms didn’t come here accidentally. What if the alien life out there was intelligent
and advanced enough that they could have sent the building blocks of life towards Earth
deliberately? The first possibility of this is accidental
transport. On Earth, there have been countless cases
of people throwing trash into the water and having it be swept somewhere completely different
- often endangering animal life in the process. It’s possible that an alien civilization
would have been advanced enough to send waste products into space and dump them on an uninhabited
world - that thanks to the trace DNA on the waste, evolved into the Earth we know today. But other theories say that the seeding of
Earth may be much more deliberate. Directed panspermia is the idea that an alien
species created life on Earth via transport of organisms from their world. The idea of a deliberate seeding of the planet
sidesteps a lot of the issues with other theories - because the aliens would have been able
to shield the samples for their trip, eliminating the threat that the journey through space
or the cosmic radiation would kill off the organisms before they ever reached their target. The alien species, if advanced enough to send
samples into space, would be able to send them at high speeds that would allow them
to reach their destination in a more feasible time. So why would aliens want to seed our planet? The first possible theory is that the aliens
were looking to secure and protect life in space by spreading it among a larger area. Even the strongest civilization can be felled
by a natural disaster or stray comet, and when life exists on more than one world, it’s
insured against the whims of the cosmos. Of course, that was 3.5 billion years ago,
and the odds are good that any alien civilization that seeded Earth at the dawn of our world
would be long gone themselves by now. But what if they weren’t? There are many theories about aliens making
contact with Earth, but thus far no conclusive proof has been found - regardless of how many
people say they were abducted by a flying saucer. But if aliens are out there - and may even
have ties to the creation of life on Earth - then why haven’t they made contact yet? One theory is that they simply don’t want
to - they’re more than happy to just watch. This is called the Zoo Hypothesis, and it
states that we’re all essentially living in a giant terrarium. Whatever these aliens are, they have technology
far beyond ours and they’re perfectly happy watching as our still-primitive planet slowly
evolves. If we don’t know about their existence,
it’s because they don’t want us to know - yet. So are there any problems with this idea? Just one big one - have you ever tried to
get a group of people to agree on anything? Trying to get ten people to agree on one place
to eat is hard enough. Imagine how difficult it would be to get an
entire civilization to agree to keep a secret forever without any of them breaking the code
of silence and broadcasting their existence to our “human zoo”. It would have had to last millions of years
of humans and their ancestors existing, and likely countless generations of the aliens
not breaking their own protocol. That’s why many people say the Zoo hypothesis
resembles creationism and religious theory more than panspermia. But have the aliens truly maintained a hands-off
approach all this time? A popular idea - but maybe not so popular
among scientists - is that Earth has been visited repeatedly by advanced alien civilizations
that may have interacted with humans before recorded history. Called the Ancient Astronauts theory, it often
has ties to various religions - after all, how many religious texts refer to powerful
and mysterious beings descending from the heavens and performing miracles? But is there any evidence of these interstellar
visits? If you watch a program called Ancient Aliens
- a lot! This popular documentary-style series looks
at evidence of alien interactions with humans, with a particular focus on early civilizations
and the idea that certain technology and buildings couldn’t have been constructed by pre-industrial
humans alone. They look at mythology of giants and Gods,
massive structures like the pyramids that show up across the world, and technology that
seems too advanced for the time like the massive clockwork Antikythera Mechanism of ancient
Greece. With sixteen seasons and almost two hundred
episodes, there are a lot of believers. But just as many detractors. The Ancient Astronauts theory - and Ancient
Aliens in particular - has been criticized for using selective evidence and disregarding
the contributions of early Native cultures. The construction methods for megalithic structures
like Stonehenge, the Great Pyramids of Egypt, and the Mayan pyramids have been investigated
and largely proven. While there are still a lot of mysteries surrounding
ancient architecture, like the giant stone spheres of Costa Rica, few of them seem to
point to aliens - but that hasn’t stopped the speculation from growing. We don’t know for sure if aliens have visited
Earth - but there’s a chance that their DNA is still with us. We might all be descended from aliens, if
their organisms seeded our world eons ago. The most likely scenario, if we evolved from
alien microorganisms, is that we’re so radically different from the original species by now
that there would be no similarity anymore. If an alien species did seed Earth deliberately,
then the odds are it didn’t seed Earth with the most advanced form of life on its planet
but one of the smallest and easiest to transport. The continuum of life on Earth indicates life
likely started with microorganisms swimming in the water before turning into larger forms
of life and eventually heading onto land - a far cry from the aliens who might have organized
Earth’s seeding. But could humanity’s ties to alien DNA be
a lot more recent? Many proponents of the Ancient Astronauts
theory suggest that the aliens may have continued to visit Earth up until the early days of
humanity, and may have actually bred with humans - leaving traces of their DNA in ours. While the idea of aliens on a pleasure cruise
looking for some exotic party times may be relatable - especially if they have common
DNA with those party kids who hit Cancun every Spring Break - there are a lot of holes in
the theory. The aliens would have to still be around and
in a similar shape billions of years after Earth was first seeded, and they would have
to be genetically compatible with humans despite those billions of years of evolution. So, no, it’s not very likely that your great-great-great-great-great
grandpa was an alien. But that doesn’t mean this kind of interbreeding
between humans and their distant relatives isn’t possible. Recent studies indicate that human fossils
have traces of DNA from ancient humans that preceded Homo Sapiens. The more famous Neanderthals are in there,
but so are an extinct species of archaic humans we know relatively little about - the Denisovans. Only identified in 2010 in Siberia, they’ve
been identified from a few bones and teeth that are distinct from other species. When ancient genomes were sequenced for the
first time, scientists found fragments of genetic code that didn’t match up with Homo
Sapiens. Neanderthals were quickly identified - in
fact, it’s estimated that most humans besides Africans have up to four percent of trace
Neanderthal DNA in their genome. No one knows exactly what populations of ancient
humans may be lurking in the recesses of the human genome, both ancient and modern. What we do know is that modern humans are
a complex mix of influences that made us what we are. Could one of those influences be from beyond
our solar system? We don’t have proof of that yet - but the
human genome is a mystery, and we don’t have proof that it’s impossible either. For more on alien visitors, check out “This
Will Happen When the Govt Confirms Aliens Exist”, or watch “How Did the Dinosaurs
Die” for more on the chaos objects from space can cause.
