That time 96.7% of humans died... 人類の96.7%が死んだ時代

寒冷により、地球上の人類が600人まで減った時代があったそうです。

80億人が生きる現代世界で言うと、日本人以外の人間が全ていなくなるようなインパクトです、とんでもないですね。

こういう話はthrillingで面白いです

それでは今日もYouTube英語を楽しんでいきましょう！

00:01
imagine waking up tomorrow to find out
00:03
an
00:03
unstoppable natural disaster is about to
00:06
wipe out the entire population of the
00:08
human race
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or to be more specific 96.7
00:13
of it sounds pretty scary right
00:15
thankfully
00:16
it doesn't look like that's going to
00:17
happen to us anytime soon
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but that isn't to say it hasn't happened
00:21
before these
00:22
near-extinction circumstances were a
00:25
reality for our ancestors at one point
00:27
in history
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so let's rewind the clocks to that time
00:30
96.7 percent of humans died
00:33
[Music]
00:38
there are close to 8 billion human
00:40
beings alive today
00:41
with such an enormous population it's
00:44
hard to imagine that we were once an
00:45
endangered species but it's true at one
00:48
point
00:49
we were a turn of bad luck away from
00:51
being wiped out completely
00:52
but thanks to a little sprinkling of
00:54
good fortune and the impressive
00:56
intelligence of our ancestors we're
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still here today
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want to know how we managed it well
01:01
strap in folks cause we're going on a
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journey
01:04
back in time 195
01:07
000 years ago the world was almost
01:09
unrecognizable compared to what it's
01:11
like today
01:12
there were no cities or cars no cell
01:14
phones or fast food restaurants
01:16
and there was certainly no wi-fi but the
01:19
most significant differences between
01:21
earth and 2020 and earth 195 millennia
01:24
ago
01:25
were in the temperature and climate back
01:27
then planet earth was starting to get
01:29
very very cold because of something
01:31
called the big chill
01:33
or if you want to get all scientific
01:35
marine isotopes stage six
01:37
what is a marine isotope stage i hear
01:39
you ask
01:40
well marine isotope stages are
01:42
alternating warm and cool periods in the
01:44
history of earth's climate
01:46
these varying stages are assigned higher
01:48
numbers the further back in earth's
01:49
history they occurred
01:50
and are measured by scientists studying
01:52
data from deep sea core samples
01:55
the levels of an isotope of oxygen known
01:57
as oxygen 18
01:59
in a sample reveals information about
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how prevalent
02:02
ice sheets were at the given time the
02:04
more oxygen 18 absorbed by the sediments
02:07
around the world
02:08
including the bottom of the oceans the
02:10
more severe glacial buildups of ice were
02:12
in that period
02:13
the period we are currently living in is
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classed as marine isotope stage 1
02:18
making a nice and toasty segment of
02:20
earth's history
02:21
marine isotope stage 6 meanwhile lasted
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from 195
02:25
000 years ago until 123 000 years ago
02:29
and samples from the period show high
02:31
levels of oxygen 18.
02:33
with this info we know earth was going
02:35
through a particularly chilly time
02:37
which experts refer to as a glacial
02:40
period
02:40
our ancestors meanwhile probably
02:42
referred to it as
02:43
really bad news at least they would have
02:46
if they understood modern languages
02:50
the temperature which had previously
02:51
been warm enough to support plant and
02:53
animal life over great expanses of the
02:55
earth
02:56
plummeted compared to our modern day
02:58
global averages
02:59
the global temperature was 10 degrees
03:01
celsius or 18
03:02
fahrenheit lower needless to say that
03:05
kind of chilliness had some serious
03:06
effects on the world
03:08
this freezing weather triggered drought
03:10
conditions so severe that vast stretches
03:12
of europe
03:13
asia and much of the african continent
03:15
were virtually uninhabitable
03:17
neither plants nor the creatures that
03:19
ate them could survive
03:20
and life was forced into rare hospitable
03:23
pockets of warmer land
03:25
if they were lucky enough to find them
03:27
but in certain parts of the landmass we
03:29
know as africa today
03:30
conditions were just about tempered
03:32
enough for life to cling on
03:34
and as it happened that's exactly where
03:36
all the humans were
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don't get too excited though you
03:40
wouldn't find any kingdoms cities or
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even towns
03:43
for these things to exist you need a lot
03:44
of resources
03:46
for one thing and during a glacial
03:48
period the circumstances made the
03:49
emergence of larger settled communities
03:52
unviable but for the homo sapiens that
03:54
were around
03:55
africa was home in fact humanity didn't
03:58
expand beyond the borders of africa
04:00
in large numbers until around 70 000
04:02
years ago
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which makes sense in light of the small
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size of the population and scarcity of
04:07
available resources at home
04:09
and elsewhere to support long-distance
04:11
exploration
04:12
at this time human communities were
04:14
small nomadic and spaced out
04:16
and the total global human population
04:18
was tiny even in good times
04:20
for much of their existence ancestors of
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modern humans
04:23
including populations of non-homo
04:25
sapiens like homo erectus and homo
04:27
neanderthalensis
04:29
maintain this trend of very small
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populations
04:32
the entire human breeding population
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hovered between ten thousand and thirty
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thousand people
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starting at about four hundred thousand
04:39
years ago for perspective the number of
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humans at this time was comparable to
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the number of polar bears on earth today
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this human population size isn't
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believed to have begun substantially
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expanding for another 350
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000 years but somewhere in the middle of
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all that
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the big chill dawned and brought those
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numbers to breaking point
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when the marine isotope stage six was in
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full swing
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winter was no longer coming it was here
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and it was
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nasty humanity's ancestors so far had
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enjoyed a rather warm existence hunting
05:10
and gathering under the african sun
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but now their very survival was thrown
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into question
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with huge amounts of the earth's liquid
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water becoming trapped in glaciers
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the deserts expanded leaving almost
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everywhere
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barren cold and dry with habitable land
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gradually becoming scarcer and scarcer
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early humans were left with only two
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options either sit it out and freeze or
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starve to death
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or pack up and run unfortunately a
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significant portion of existing humans
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didn't have the ability or awareness to
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move in time
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or were simply too far from habitable
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hot spots and perished
05:45
many other humans split up into smaller
05:47
less stable populations looking for more
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habitable lands
05:50
only a lucky few reach their
05:52
destinations
05:54
with danger and death at every turn at
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the most challenging points of this
05:58
period
05:58
the total human population is estimated
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to have dropped as low as 600 people
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yep you heard that right 600
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marine isotope 6 almost wiped out the
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entire human population
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which is thought to have set at around
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18 000 before the big show really hit
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by our best estimates a staggering 96.7
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percent of the human population died out
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leaving 3.3 remaining with the weight of
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humanity's future on their shoulders
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considering how small the population had
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already been beforehand
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humanity was facing extinction before it
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had even gotten properly started
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that small band of humans that did
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survive managed to escape the expansion
06:41
of the arab deserts and glaciers by
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moving down to the south african
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coastline
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in these more forgiving climates our
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ancestors could put their already
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impressive intellect to good use
06:50
taking advantage of the available
06:52
resources in fact some experts have even
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suggested that the intelligence
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demonstrated in our ancestors abilities
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to move around and adapt was what
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allowed us to survive
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against all odds put bluntly when faced
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with apocalyptic scenarios
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it pays to be smart the greener or bluer
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pastures the remaining humans moved to
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were always close to the sea
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which proved a vital factor in the
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survival of the species
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so why is the sea so special well for
07:19
starters
07:20
the ocean in these regions had
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alternating warm and cold currents
07:23
which meant it was absolutely teeming
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with marine life
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this included nutrient-rich foods like
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sea snails alongside the occasional seal
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and whale
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although no single food source was more
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significant than shellfish
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which thrived along the south african
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coast these tasty marine treats were an
07:40
excellent source of protein for the
07:42
humans
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and there were plenty of them to go
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around all year long
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considering how scarce food was
07:48
everywhere else some experts even
07:50
suggest that at this point in our
07:51
history
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the sea was responsible for the survival
07:54
of humanity
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but while there's certainly some truth
07:57
in that claim the sea wasn't the only
07:59
source of food in these tempered lands
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there was an incredible diversity of
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plant life to be found as well
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the region featured an abundance of
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plants adapted to survive through the
08:08
increase in cold temperatures using
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underground storage organs which
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contained high quality carbohydrates
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making them a great energy source and
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when the weather permitted
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open grassy plains to arise our
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ancestors would go hunting large mammals
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like antelope
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all in all as far as post-apocalyptic
08:25
hideouts go
08:26
humanity really struck the jackpot with
08:28
this area of south africa
08:30
compared to the arid wastelands further
08:32
north the coastal regions of the south
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were like the garden of eden
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those living there had a plentiful
08:37
varied and nutritious day
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and we're in the perfect environment to
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start rebuilding the population
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if you know what i mean it wasn't all
08:45
fun and games though
08:46
the smaller populations were far more
08:48
susceptible to diseases and
08:50
environmental disasters
08:52
this meant that even among those who
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found refuge the dispersed populaces of
08:56
entire areas could be wiped out in the
08:58
event of something like a virus outbreak
09:00
or flood
09:00
plus unfavorable genetic traits like
09:03
hereditary illnesses can be passed on
09:05
rapidly in smaller gene pools with so
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few humans remaining
09:09
this was a very real threat to
09:11
humankind's survival
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with so many odds stacked against them
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it's pretty miraculous that our hearty
09:16
ancestors survived in their small groups
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even once the worst of the big chill was
09:21
over but the chill didn't come and go in
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a few months
09:24
or a year or two or even a decade the
09:27
big chill of marine isotope stage six
09:29
lasted for more than 70 thousand years
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countless generations of humans lived
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and died during this unforgiving stage
09:37
in earth's geographical history
09:39
with many never knowing what a warm
09:41
summer's day felt like
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pretty sad isn't it of course the humans
09:44
who lived during these cold dark days
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didn't know any different
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which was probably for the best but just
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because survival was the main focus day
09:52
in day out
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that didn't mean it's all they thought
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about we need only look to the caves
09:56
that many of our south african
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survivalist ancestors called home for
10:00
proof of that
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the human survivors of the big chill
10:03
were a heck of a lot bradier than you
10:05
might imagine
10:06
and not just because they were smart
10:07
enough to live down south
10:09
in fact their creative thinking and
10:11
reflection is thought to have
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contributed significantly to their
10:14
ability to thrive in spite of the
10:15
challenges they faced
10:17
along the klossy's river in south africa
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there are a series of caves that were
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once home to some of those 600 or so
10:23
survivors of the big chill
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one of these caves given the slightly
10:27
underwhelming name pp13b
10:30
contains artifacts that suggest huge
10:32
leaps in human cognition were made by
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our ancestors who resided there
10:36
evidence from the cave shows that they
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used the shellfish they hunted not only
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as a tasty food source
10:41
but also as decorations keeping hold of
10:44
shells purely for their beauty these
10:46
decorative shells paired nicely with
10:47
their love of carving and early paint
10:49
work
10:49
usually using iron pigments and animal
10:52
fats the cave dwellers would also treat
10:54
their weapons and tools with fire making
10:56
them stronger and more effective
10:57
before the discoveries in the pp13b cave
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this method of heat treatment was
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believed to have originated in france
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only 20 000 years ago
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as it turned out our clever old
11:08
ancestors were about a hundred thousand
11:10
years ahead of the curve
11:11
with the advanced intelligence on show
11:14
it's highly likely that the ingenuity of
11:16
survivor groups like these contributed
11:18
to their ability to survive the big
11:20
chill
11:20
or quite possibly the toughness of their
11:22
circumstances forced them to adapt
11:24
intelligently more than ever
11:26
after all they say necessity is the
11:28
mother of invention
11:30
whichever way around it was though
11:31
without their impressive intellect
11:33
none of us would be here to learn about
11:35
these tough survivors today
11:37
you might have noticed that i'm
11:38
referring to these survivors as our
11:40
ancestors
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and this isn't just a generalization
11:43
with the severity of the big chills
11:45
decrease in human population
11:47
there's a high chance that every single
11:49
person you've ever met
11:50
or will ever meet shares ancestors with
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those 600 or so survivors this is
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because following the catastrophic
11:57
events of marine isotope stage six
11:59
the human population bottlenecked with
12:02
population bottlenecks there are two
12:04
potential paths
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either the species goes extinct or it
12:08
recovers
12:08
albeit with greatly reduced genetic
12:10
diversity with even a slight shift in
12:13
the variables humanity might have
12:15
never surpassed this bottleneck becoming
12:17
nothing more than another blip on the
12:19
radar of earth's natural history
12:21
in this case thankfully humanity
12:23
recovered but the way in which we
12:25
survived raises an interesting point
12:27
being that we're very likely all
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descended from this merry band of
12:30
survivors
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it means our genetic diversity is
12:33
relatively minimal compared to other
12:35
animals
12:36
had this big chill not occurred and had
12:38
a more genetically diverse range of
12:40
humans continued to exist
12:41
we may never have had such a strong
12:43
imperative to pull together in larger
12:45
communities
12:46
the differences between our ancestors
12:48
and other slightly genetically different
12:50
groups of humans may have proven too
12:51
great to overcome
12:53
there may even have been a state of
12:54
constant war between different types of
12:56
humans had a wider variety survived
12:59
and who's to say our ancestors would
13:01
have won and not been wiped out by
13:03
others whose genetics afforded them
13:04
greater strength or increased
13:06
intelligence without needing to unite as
13:08
one in the face of near extinction
13:10
civilization may never have arisen at
13:12
least none the way we understand it
13:14
but as we know civilization did arise
13:17
because we
13:18
were able to work together with this
13:20
narrow escape in our shared genetic
13:22
history
13:22
it seems human to human connection
13:24
really is in our blood
13:25
perhaps that's why socialization is so
13:28
important to us
13:29
well most of us but seriously what if
13:31
the further we stray from seeing
13:33
humanity as one big family
13:34
the greater the obstacles to our future
13:36
become after all
13:38
the entirety of humanity was once
13:39
encapsulated in a small group of 600
13:42
fighting for our species survival and
13:45
we're all descended from them
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weird to think about isn't it so where
13:49
did humanity go once the big chill was
13:51
over
13:51
well 70 000 years after the glaciers
13:54
expanded and humanity was knocked to its
13:56
knees
13:56
the ice began melting away and life
13:59
returned in spectacular fashion
14:01
perhaps fed up of being stuck in the
14:03
same place for over 700 centuries
14:06
though more likely through the opening
14:07
of new food opportunities
14:09
the early humans started to move out as
14:11
far as we can tell
14:12
they first expanded out of east africa
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into asia before spreading out across
14:16
the globe
14:17
but it wasn't an easy ride for humanity
14:19
and plenty more disasters struck along
14:21
the way
14:22
like the toba super volcano eruption 75
14:25
000 years ago which spewed enough
14:27
noxious material into the air to largely
14:29
block out the sun for years
14:31
killing off countless human communities
14:33
in the process we faced another ice age
14:35
too
14:36
but survived once again by heading to
14:38
the sunny southern regions and using our
14:39
intelligence to adapt
14:41
despite a seemingly endless barrage of
14:43
challenges humanity repeatedly triumphed
14:46
over extinction
14:47
it took until 1804 ce for the population
14:50
to finally reach the milestone of 1
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billion people
14:53
and thankfully or unfortunately
14:56
depending on your perspective
14:57
our numbers haven't shown any signs of
14:59
slowing since
15:00
i'll let you decide whether that's good
15:02
or bad in the comments below
15:04
but whatever your general view of
15:06
humanity one thing remains true
15:08
without these early humans intelligently
15:10
adapting to life in the hardest
15:12
circumstances imaginable
15:14
and eating a lot of shellfish humanity
15:16
would have been wiped out 195
15:19
000 years ago you wouldn't be watching
15:21
this video right now
15:22
or browsing on the web or even existing
15:24
at all
15:25
these hearty survivors are the real
15:27
heroes of the human race
15:29
and deserve to have their story told the
15:31
story of the time humanity was saved by
15:33
a winning combo of our big brain smarts
15:36
and the big blue sea do you think
15:40
you could survive a day in marine
15:41
isotope stage six's big chill
15:43
let me know in the comments below thanks
15:45
for watching
15:58
you