Un Événement Auquel Seulement Un Millier D’êtres Humains Ont Survécu

Sympa

Il y a environ 800 000 à 900 000 ans, un goulot d'étranglement génétique s'est produit, réduisant drastiquement la population humaine. Cet événement a entraîné l'extinction de 98,7% de la population, ne laissant qu'environ 1 280 individus. La cause principale était un changement climatique significatif appelé la transition du Pléistocène moyen, qui a apporté des cycles glaciaires plus longs et plus rigoureux. Ce changement a rendu la chasse difficile pour les premiers humains, les obligeant à s'adapter tandis que certains animaux disparaissaient. Les scientifiques étudient encore la cause exacte et le moment de ce goulot d'étranglement.  Animation créée par Sympa. ---------------------------------------------------------------------------------------- Musique par Epidemic Sound https://www.epidemicsound.com   Pour ne rien perdre de Sympa, abonnez-vous!: https://goo.gl/6E4Xna​ ---------------------------------------------------------------------------------------- Nos réseaux sociaux : Facebook: https://www.facebook.com/sympasympacom/ Instagram: https://www.instagram.com/sympa.officiel/  Stock de fichiers (photos, vidéos et autres): https://www.depositphotos.com https://www.shutterstock.com https://www.eastnews.ru ----------------------------------------------------------------------------------------  Si tu en veux encore plus, fais un tour ici:  http://sympa-sympa.com

Transcript

00:00Can you imagine that all human beings today are made up of only a thousand people?

00:05Some 800 to 900 thousand years ago, almost all of our ancestors disappeared,

00:10leaving behind only a small percentage of the population.

00:14So what happened?

00:17The Earth is known for frequent ice cycles, we call them ice periods.

00:21In the past, these periods were rather soft and occurred regularly,

00:26about every 41,000 years.

00:28Ice periods are linked to the axis of the Earth.

00:31Our planet, being slightly inclined, its axis is not straight.

00:35Over the millennia, this inclination has slightly changed.

00:38This tiny change affects the amount of sunlight we receive,

00:42especially at the poles,

00:44and leads to episodes of cooling or warming of an incredible intensity.

00:48About 2.6 million years ago, when the first humans settled on Earth,

00:53the Pleistocene era began.

00:56This is the era we traditionally call the Ice Age, as in the movies.

01:00Large ice caps covered certain parts of North America, Europe and Asia.

01:07Ice was not everywhere all the time.

01:09These ice cycles went and came, and sometimes the caps melted temporarily.

01:14But overall, the conditions were much colder than today.

01:18We can still see proof of this.

01:21Glaciers dug valleys and left behind them impressive formations such as moorings and fjords.

01:29And as the sea level was very low, a large part of the world was made up of land.

01:34This allowed humans and animals to travel between continents and spread everywhere.

01:39It was the era of the megaphone.

01:41You discovered it in the movies.

01:43Mammoths, hyenas, felines with saber-toothed teeth, giant parrots and mastodons.

01:50Our ancestors spent their time hunting all these giants.

01:53Man is not made up of a single line.

01:55It is not as if monkeys slowly transformed into humans.

01:59We are made up of different species.

02:01Homo erectus, Neanderthal, etc.

02:05But only one species, Homo sapiens, survived and became modern man.

02:10Difficult conditions forced us to become smarter.

02:14We learned to make tools, clothes and shelters to survive.

02:18We became hunter-gatherers and invented fire, which proved very useful during the Ice Age.

02:25And yes, a big unexpected change was about to happen.

02:28A disastrous event occurred about 850,000 years ago.

02:32Humans had to face a major demographic collapse.

02:36Only 1,280 people survived.

02:39About 99% of the first humans were annihilated.

02:43And we, we are below the small percentage that survived.

02:47This near-extinction is, unsurprisingly, imputable to the climate.

02:51This is the transition of the average Pleistocene.

02:54The orbit of the Earth around the Sun has slightly changed.

02:58Carbon levels have fallen.

03:00A lot of things have happened.

03:02And the climate of the Earth has become incredibly cold and dry.

03:07The seas have suddenly become colder.

03:09And Africa and Eurasia have had horrible periods of drought.

03:13It was almost impossible to find food.

03:16Scientists learned all this by collecting DNA from about 300,000 people around the world.

03:21They used a new method that allowed them to trace the history of human evolution over a million years and learn more.

03:29It is not surprising that there are practically no fossils of this time.

03:33There was almost no one.

03:35What is interesting is that before that, most monkeys had 24 pairs of chromosomes.

03:40But when the population shrank, two pairs merged and we ended up with only 23 pairs.

03:46It was the drop of water that overflowed the vase and separated us from the other monkeys.

03:51Chimpanzees, gorillas and orangutans all have 24 pairs of chromosomes.

03:56But our fused chromosome has become the human chromosome.

04:01As a training effect, this little thing influenced our brain.

04:04Then we started walking on two feet and we invented language.

04:09It took humans about 100,000 years to recover from this disaster.

04:13It is only after all this time that they began to spread again.

04:17Isn't it incredible that we have gone from 1,000 to 8 billion individuals?

04:21Anyway, the Ice Age finally ended about 1,700 years ago.

04:26A warmer period, called Holocene, began.

04:30With warming, human civilizations were finally able to develop.

04:355,000 years ago, it was Ancient Egypt, then the civilization of the Indus Valley, Ancient China and many others.

04:43Although we have prospered for a while, a problem remains.

04:47The transition of the Middle Pleistocene changed the duration and intensity of the glacial cycles.

04:52Before the transition, there were many glacial eras, but the cold was softer and the cycles shorter.

04:58The Earth was covered with a layer of ice every 4,000,000 years or so.

05:02But after the transition, the glacial periods have become longer and more rigorous.

05:07The cycles have changed.

05:09They occurred every 100,000 years, but they were very intense.

05:13The glacial plates have enlarged, even extending to the south.

05:17From now on, the glacial periods that will continue to occur will be a little different.

05:23The next one should take place in about 50,000 years, maybe later.

05:27And later will be the best.

05:29But at the same time, the consequences will be much worse.

05:32What our ancestors lived is called a demographic stranglehold.

05:36This is how we call a sudden and significant reduction in the size of a population.

05:41This usually occurs as a result of earthquakes, floods or droughts, fires and even human actions.

05:49Only a few people survive.

05:51And they alone can transmit their genes to future generations.

05:55And such strangleholds, there have been many in history.

05:59Our modern species, the Homo sapiens, originally lived in Africa.

06:04About 60 to 80,000 years ago, a small group of them left Africa and spread throughout the world.

06:11It was not on a whim.

06:13They had to move due to droughts and the enormous climate problems that Africa knew at the time.

06:19They went in search of food and found new places to live.

06:23They crossed the Middle East, then Europe and Asia, before reaching Australasia and the Americas.

06:29They quickly settled on different continents and began to mix with indigenous species,

06:35like the Denisovans and the Neanderthals.

06:38But there was a problem.

06:40Originally, African species were extremely diversified in terms of genetics.

06:45But as only a small part of them went to settle elsewhere, most of these genes could not be disseminated.

06:52And this caused a lot of strangleholds for everyone.

06:55Species similar to humans, which then emerged in other parts of the world, began to present a smaller genetic diversity.

07:03Their genetic heritage being more restricted, they became more vulnerable to various substances.

07:08The African population also experienced a decrease in its genetic diversity.

07:13But at least humans managed to survive.

07:17However, the non-African populations eventually fell and the Neanderthals and Denisovans disappeared.

07:23Only we, the Homo Sapiens, remained.

07:26This is why we can say that all modern men are from Africa.

07:32The first men lived a hard life.

07:34About 74,000 years ago, they suffered a new catastrophe, the Toba Catastrophe.

07:40But this is only a hypothesis.

07:42It is not certain that this catastrophe actually occurred.

07:45In fact, scientists believe that there was a super volcanic eruption on the current site of Lake Toba in Sumatra, Indonesia.

07:52This eruption would have been absolutely catastrophic for the climate and for man.

07:57This was one of the most powerful volcanic events of the last two million years.

08:01The volcano would have spit between 3,000 and 6,000 cubic kilometers of lava and volcanic matter.

08:07As a reminder, there are about 13,000 cubic kilometers of water in the entire atmosphere of our planet.

08:12It is ... to say if it was a lot of lava.

08:15This terrible catastrophe led to the formation of Lake Toba, a huge lake of caldera in Sumatra.

08:22Tons of ash and sulfur dioxide have also been rejected into the atmosphere.

08:27This caused what is called a volcanic winter.

08:30That is to say that, even if it is not really winter, temperatures drop and the planet freezes because all these ash clouds prevent the sunlight from reaching the earth.

08:39This event has affected climate patterns for years, even decades.

08:44It has also very likely accelerated the arrival of the next ice age.

08:48Fortunately, humans are very good at surviving.

08:52The world's human population has been reduced to a few thousand people once again.

08:57And they still managed to overcome this ordeal.

Category

Transcript

Recommended