• 2 months ago
Les anthropologues ont découvert quelque chose de plutôt fascinant à propos des Néandertaliens—ils pourraient ne pas avoir complètement disparu comme nous le pensions. Au lieu de cela, il semble qu'ils aient pu être absorbés dans le pool génétique des humains modernes. Une nouvelle étude montre que l'ADN des Néandertaliens pourrait inclure jusqu'à 3,7 % de gènes humains modernes. Cela suggère que les humains et les Néandertaliens se sont croisés plus que nous ne le réalisions auparavant. Ainsi, d'une certaine manière, les Néandertaliens sont toujours avec nous aujourd'hui, juste mélangés dans notre ADN. Animation créée par Sympa.
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Transcript
00:00You are much more Neanderthal than you think, at least as far as your DNA is concerned.
00:06These ancient hominids were no more cunning and more robust than today's humans.
00:11They made stone tools, mastered fire, wore clothes, and practiced certain specific rituals.
00:18The official theory would like them to be extinct 40,000 years ago.
00:22However, a new study suggests that it is likely that the Neanderthals were never completely extinct,
00:28but rather merged with modern humans.
00:30It would seem that every current human being has about 3% of the Neanderthal genome in its DNA.
00:36If this is true, it would indicate that the Neanderthals were much more linked to our ancestors than we thought,
00:43sharing with them a long history of cohabitation.
00:46The Neanderthals were close relatives of modern humans,
00:50but our lines separated about half a million years ago.
00:53More than 10 years ago, scientists discovered that the Neanderthals formed families with the first humans who left Africa.
01:01As a result, the populations living today outside Africa have about 1 to 2% of Neanderthal DNA in their genetic heritage.
01:10To date, we have only three truly conclusive examples of complete genetic codes from these ancient hominids.
01:18The first comes from bones discovered in a cave in Croatia, dating from 50 to 65,000 years.
01:23The other two examples, aged about 80,000 and 50,000 years, were found in two caves located in Eurasia.
01:30Scientists are not yet sure how the DNA of modern humans entered the genetic alphabet of the Neanderthals
01:37due to the lack of material to study.
01:40However, by comparing the DNA of three Neanderthals with that of 2,000 modern humans,
01:45they discovered that this DNA could contain up to 3.7% of human genetic code.
01:51This would mean that in the ancient Neanderthal population, about 1 in 30 parents were a Homo sapiens.
01:59Researchers have discovered that the DNA of modern humans had integrated into the Neanderthal genetic heritage
02:04during at least two distinct periods of interbreeding between the two species.
02:09The first would have taken place 200,000 to 250,000 years ago,
02:13and the second, about 100,000 to 120,000 years ago.
02:16It is possible that other periods of interbreeding existed,
02:20but they are not observable in the DNA sequences we have today.
02:25Another recent study, which is not yet unanimous within the scientific community,
02:30suggests that the majority of the Neanderthal DNA present in modern humans
02:34would come from a single large period of interbreeding that occurred about 47,000 years ago
02:39and that would have lasted about 6,800 years.
02:42Cranes dating from almost 100,000 years ago were discovered in two caves in the Middle East.
02:46These cranes, which seem to belong to some of the first modern humans,
02:50have characteristics like more prominent archaic eyebrows,
02:54suggesting the presence of Neanderthal DNA.
02:57This could be explained by a genetic flow of Neanderthals
03:00that would be part of the period of interbreeding mentioned.
03:03The study also looked at the genetic divergences between the three Neanderthal genomes available,
03:09revealing that their population was even more reduced than previously believed.
03:13This observation could be a new proof that Neanderthals have not simply disappeared,
03:18but that they have actually merged into the genetic heritage of modern humans.
03:22Many Homo sapiens groups have left Africa
03:25and have mingled with the Neanderthals so much that they could not remain apart.
03:30In the future, researchers aim to explore the impact of modern human DNA on Neanderthals,
03:37which could shed light on the positive or negative consequences of such a mingling.
03:41Neanderthals are not our only distant ancestors.
03:45In the past, at least nine human species populated our planet.
03:49One of them, Homo habilis, nicknamed the Skillful Man,
03:53owes its name to the discovery of stone tools among its remains.
03:57This hominid lived in East and Western Africa 2.4 to 1.4 million years ago.
04:03Homo habilis was distinguished by a slightly larger brain than its predecessors
04:08and a face reminiscent of that of large apes.
04:10Homo habilis measured about 1.20 meters and had a varied diet.
04:15For a long time, scientists have considered it the oldest member of the human line.
04:20However, new dating methods have revealed that Homo erectus, another hominid,
04:26could be older and not be directly related to Homo habilis.
04:31Homo naledi, discovered in 2013 in a cave in South Africa,
04:35is an even more enigmatic member of our human family.
04:39It is the only region in the world where these remains have been found.
04:42Although they moved standing up, measuring about 1.40 meters for a weight of about 40 kilograms,
04:48they were also adept at climbing.
04:51Their brains were small and we know little about their way of life,
04:55because no stone tool or other cultural element has been discovered.
04:59However, some scientists hypothesize that they may have buried their dead and practiced the rupestre.
05:06In 2010, fossils were discovered in a cave in Siberia,
05:10but their belonging to a specific species remained uncertain.
05:13These fossils are those of the Denisovans,
05:16a group that lived between 1904 and 5,000 years BC.
05:21Although few Denisovan fossils have been discovered,
05:24DNA analysis has revealed that they were closely related to Neanderthals and modern humans.
05:30They even formed families with the first humans, especially in Southeast Asia.
05:35Due to insufficient fossils, the Denisovans did not receive distinct species names,
05:40but their genes are found in the DNA of current humans,
05:43suggesting that they could belong to our own species.
05:47As researchers deepen their studies on Denisovans and fossils discovered in Asia,
05:52our understanding of the different human species and their place in our genealogical tree could be refined.
05:59In 2003, fossils of a very small human species were discovered in a cave on the island of Flores, Indonesia.
06:07These individuals, belonging to the Homo floresiensis species,
06:12lived from 100 to 5,000 years BC.
06:15They only measured about 1 meter in height.
06:18Scientists think that they probably descend from the Homo erectus
06:22and that they have shrunk over time due to limited food resources on this isolated island.
06:28Because of their small stature, they are sometimes nicknamed the Hobbits.
06:33About 4,000 years ago, the Homo sapiens, that is, us,
06:37were the last representatives of a diversified line of human species capable of moving on two legs.
06:44The question then arises, what have become of the other species?
06:48And did we play a role in their disappearance?
06:51Some experts suggest that our survival would be due to the increased longevity of our offspring
06:58or to our better ability to adapt to climate change.
07:02Others think that we may have competed with these other human species,
07:06or even merged with them by sharing our genes.
07:09The first Homo sapiens, which appeared in Africa about 3,000 years ago,
07:13did not look like us exactly, but they were much closer to our appearance than the other hominids.
07:19They had high and rounded skulls with almost vertical foreheads.
07:24Unlike the Neanderthals, they did not have neither the thick eyebrows nor the sagging jaws found in the Homo naledi.
07:31Interestingly, they also had a chin, a unique feature among the first humans,
07:36although its function remains a mystery.
07:39Homo sapiens lived in larger groups and had a greater genetic diversity than other hominids.
07:46This extensive social organization offered many advantages, not only for health, but also for survival.
07:53The vast networks maintained across various regions acted as a net of security.
07:59In the event of a shortage, they could turn to other groups and the latter would assist them,
08:04because they would not be considered rivals, but as one and the same family.
08:09These extensive networks also facilitated the dissemination of new ideas and inventions.
08:14A large-scale simulation revealed that the later human species
08:18were able to colonize various environments thanks to these vast networks and their remarkable ability to adapt.
08:24Although the Neanderthals were very intelligent,
08:27Homo sapiens may have had a subtle intellectual advantage.
08:31Modest inventions, such as weaving and sewing needles,
08:35could have given us a decisive advantage.
08:38Scientists have discovered traces of weaving dating back 35,000 years
08:42and sewing needles dating back 3,000 years.
08:45Weaving allowed to make baskets and nets to catch food,
08:50while sewing needles allowed to make more efficient clothes and shelters,
08:55thus ensuring heat and protection, two crucial elements for survival.

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