The migration route of early humans

Regardless of the extremely desolate place, even the most stubborn people among us have enough common sense to avoid it. Man has managed to cover many areas of the earth. However, dating back to 200,000 years ago, Homo sapiens was just a new species developed in Africa, and known ancestors such as Homo erectus and Heidelberg had already surpassed Africa to explore parts of Eurasia, and sister species such as Neanderthals and Denisova would wander there before us. At the same time, the awakening of Flores and Naledi found in Indonesia comes from South Africa (which seems to be inconsistent with the previous linear model), which reminds us well that the story of human migration in prehistoric landscape is far from simple. ?

How, when and why our compatriots and our own Homo sapiens began to move around caused a heated debate. The story of early human migration covers such a huge time span and region that there is only one explanation for all these wandering and adventurous hunter-gatherers For some groups, climate change may prompt them to find more livable land, while others may have been looking for better food sources, avoiding hostile or competitive neighbors, or maybe just curious adventurers want to change the scenery. Because there are only highly fragmented fossil records (we don't know how fragmented and what parts are missing), this problem becomes more complicated. Recently, the field of genetics has taken a step forward by analyzing ancient DNA and adding it to fossil, climate and geological data.

However, with the excavation of new bones and the discovery of tools, more and more DNA is studied more and more accurately, and the story will change constantly-at least in details, but it may even be a considerable reform. Here, we will provide a basic overview based on what we think we know now, and discuss the possible motives that many different early humans may have to leave their homes and migrate to distant areas on our planet.

Early transcontinental adventurers

The flores people found in Liangbua, Indonesia may be descendants of early unknown African immigrants.

Millions of years ago, apes in the middle and late Miocene-including our ancestors and apes-existed not only in Africa, but also in parts of Eurasia. However, our own branch was developed in Africa; Among Australopithecus, we should be ancestors, living in the grasslands of eastern and southern Africa. It seems that the earliest man found safely outside Africa was Homo erectus about 2 million years ago. When interpreted broadly (there is still some controversy about which fossils should be included in the species), it is considered to determine the height of the bar, and the bar does span an impressive geographical range.

However, a very tricky place, Homo sapiens flores (nicknamed "Hobbit") found in Indonesian Liang Ya must also be named; It may be a descendant who migrated from Africa very early (before or shortly after Homo erectus), which is still unknown. In any case, clues about human migration that may have predated Homo erectus are constantly emerging. So far, five or six locations in Eurasia have spanned the suggested time range of about 260 to 2 million years ago, and these sports tools are made by unknown species; For example, the recent discovery of Chen in the Loess Plateau in southern China shows that the human beings there can be traced back to 265,438+million years ago. John hawkes, a paleoanthropologist, suspected that "as early as 2 million years ago, there had been a lot of migration and it spread from Africa to Africa." (Eagle, July 18, 20 12). The main models followed today-? As the first person to travel around the world from Africa to Eurasia, Homo erectus seems unable to explain all the evidence that appears today. However, because we don't have enough materials to enrich a more complicated story, Homo erectus certainly still plays an important role in the story of our early human migration.

About 6.5438+0.9 million years ago, Homo erectus appeared in East Africa and other places in Turkana Basin of Kenya, and Homo erectus can also be seen in South Africa and North Africa. It is generally believed that they left Africa about19-180,000 years ago, crossed the Middle East and Caucasus, and then reached Indonesia and China, and arrived about17-160,000 years ago. As early as about 800,000 years ago, Homo erectus might even bravely face the usually cold weather in northern China in a slightly mild period.

Follow-up staff

Homo erectus has set a trend for the far-reaching early human migration, and their successors will further break through the boundaries. About 700,000 years ago (perhaps as early as 780,000 years ago), people thought that Heidelberg people were developed from Homo erectus in Africa. There, different bands established their own territories in East Africa, South Africa and North Africa. Of course, in general, intra-African migration has also occurred.

Since then, a group of particularly energetic Heidelberg people have scattered in the western part of Eurasia, crossed the major mountains in Europe and extended northward to England and Germany. This is what we call ice age Europe, and these humans will have to migrate with the changing climate; They are very good at coping with the cold climate conditions in Europe, and can survive on the southern edge of the subarctic region, but naturally avoid the real ice sheet. For example, evidence from Parkfield and Hapi * * Ur in the United Kingdom shows that early humans about 700,000 years ago were indeed able to reach such a distant north when the climate was milder, and they might return to the southern refuge at a colder stage.

The Eurasian part of Heidelberg is considered to be a gradually developing species-Neanderthals. Their core home is considered to be Europe, which also needs the same high mobility and adaptability. They moved to new regions and new climatic zones, from Spain and the Mediterranean, the whole of Northern Europe and Russia, the Near East (Israel, Syria, Turkey, Iraq) to Siberia and Uzbekistan in the Far East. On the eastern edge, they slightly overlap with another species that may also cover a considerable area: Denisova, the sister species of Neanderthals. So far, only one phalanx and three teeth (from four different individuals) have been found in Denisova cave in Altai Mountain, Siberia, but genetic evidence suggests that Denisova may live in the range from Siberia to Southeast Asia. A sensational discovery found in this cave in 20 12 A.D. even directly explained the overlapping degree of Neanderthals and Denisovans: a long bone fragment was unearthed there, and the research showed that it belonged to a woman whose mother was Neanderthals and her father was Denisovans.

Homo sapiens unfolded

At the same time, at least 200,000 years ago, what we call Homo sapiens gradually began to appear, probably from the ancestors of Heidelberg in the rich territory of Africa, whether in southern or eastern Africa. Many sites have been found in these two areas, which shows that modern humans in early anatomy lived there successfully. However, they are not alone. Homo naledi, discovered in Nova Cave in South Africa in 20 13, has fossils dating from 236,000 to 335,000 years ago, adding more participants to the African stage. C. 3 15000 years ago, a species with some modern human characteristics but also some ancient characteristics-which may make them the ancestors of Homo sapiens or related branches-also lived in Jebel Irhoud, Morocco, North Africa. In addition, genetic evidence seems to show that our modern human ancestors may have contacts with other ancient groups related to them to varying degrees. The story of human evolution is not a story of the common success of a single species; This is a complex mosaic composed of different participants, many of whom may cross and/or overlap in time. ?

Members of the branch related to our modern people moved from Africa to the Near East, and the tombs of Homo sapiens were found in the ruins of Skhul and Qafzeh in Israel, dating back to 90,000 years to the shocking130,000 years respectively. Similarly, the Jebel Fa Ya site in the United Arab Emirates seems to indicate that Homo sapiens may have migrated here as early as 654.38+300,000 years ago through tools found there. Older migration is not completely impossible, because the fossil seems to be Homo sapiens (although some alternatives have been proposed), which was recently discovered in the Misria cave in Israel, with a date of about 1.8 million years ago. Far from a single migration of a species to a distant area-in any case, it doesn't make sense to think about it carefully-it seems that there are many examples of people taking many risks to wander around.

A recent study shows that some of these early explorers reached Sumatra Island in western Indonesia 73,000 to 63,000 years ago. This is closely related to other evidences, which show that human beings reached the inland of Southeast Asia at some time 60,000 years ago, and then moved northward with the retreat of glaciers. There is even new evidence that humans were located in northern Australia 65,000 years ago, which seems to have originated from early migration.

However, modern people's initial attempts to land outside Africa are dwarfed by later migrations. About 55,000 years ago, what is now considered as the "main wave" (or more likely wave) of anatomically modern people has proved to be very successful. More numbers than before quickly spread to Eurasia and other parts of the old world, and finally covered the whole world. People who participated in the recent "going out of Africa" incident seem to have a direct relationship with almost all non-Africans today, so they are considered to have replaced or absorbed most of the human beings who are already in various States. Before that, the corner of the world

About 45,000 years ago, Homo sapiens met Neanderthals, interbred with them, then branched off and eventually moved to Europe.

But which route did they choose during this long journey? As for the possible way out of Africa, Egypt is an option, but the "wet" corridor through the Sahara Desert, East Africa and the Levant is also an option. As soon as it came out, we knew through genetic research that in this environment in the Near East, human beings met Neanderthals and hybridized with them (by the way, contact with their bodies can be traced back at least 100000 years ago), then branched off and finally moved to Europe about 45000 years ago.

In Europe, modern people may quickly disperse, because new evidence shows that they seem to have arrived in southern Spain very early (such as Bajondillo Cave in Malaga). 43,000 years ago. The use of coastal corridors may have played a role in this continuous and rapid spread throughout Europe. However, Homo sapiens also continued eastward, probably all the way along the coastline, through India and Southeast Asia, where they might meet Denisovans who might live and hybridize with them (obviously, hybridization took place somewhere, and the most likely place seems to be Southeast Asia).

All this is obviously happening at a record speed. As early as 53,000 years ago, the descendants of the main wave from Africa arrived in northern Australia, while the southern part lasted until about 4 1000 years ago. However, it is not easy to achieve. Although the sea level is about 100 meters lower than today, there is still some inconvenient water between these early Homo sapiens in Asia and the land including Australia, Tasmania and New Guinea-about 70 kilometers. They may not survive such an ambitious swimming, but they built boats or rafts to help them complete this brave crossing.

At the same time, within Asia, the migration to the northern part of East Asia may have started about 40,000 years ago, paving the way for the Bering Continental Bridge, which was a side effect of the happy grassland coverage during the Ice Age, connecting Asia and America. It is generally believed that about 15000 years ago, humans arrived in America through this route, spreading down the coast or passing through the internal ice-free corridor, but this is far from a closed case. After that, some last strongholds were uninhabited for a long time, such as Hawaii (which arrived by boat around 100) and New Zealand, until around 1000.

Possible driving force

Why these prehistoric humans decided to leave and move to other places is a difficult problem to solve, especially considering that we are looking for an era earlier than written materials. However, migration is usually regarded as the result of push-pull factors, so it is a starting point. The driving factor is related to the situation that may make someone's hometown an unpleasant place, so that they give it up completely and support new things. For these early human migration, "no job" or "bad political environment" certainly does not apply; On the contrary, think about climate deterioration, turning places into huge ovens or freezers, almost nothing can survive or grow, natural disasters, competition with hostile neighboring groups,

On the other hand, the pulling factors include attracting new possibilities and returns; Basically, it is the more favorable side of the things mentioned in the "promotion" part, such as green space with better climate and abundant food and resources. Of course, this is a bit too simple, and it is difficult to track the exact combination of factors that led to every early human migration.

There are some prerequisites for successfully handling the migration. It is both tense and dangerous-for example, Homo erectus may not know what they will find after leaving Africa-and it challenges the wisdom and adaptability of a group. If you enter a new environment, it is helpful to have enough technology to help you solve it; In this case, you can successfully hunt and collect tools resident in animals and plants, or protect yourself from cold areas through clothes or fire (the latter may have been known to humans at least 6.5438+0.8 million years ago, but not used to it about 500,000-400,000 years ago). Creativity and cooperation in acquiring new resources also help.

Considering these things, there are some climate-related clues that can help us to observe the environmental aspects of immigration more carefully. Climate models have been used to show that the fresh water flux associated with the ice sheet flowing into the North Atlantic (known as Heinrich event) may lead to abrupt climate change. These events are bound to occur from time to time in the last glacial cycle, and may make large areas in North Africa, East Africa and West Africa uninhabitable because conditions become very dry. This may be a driving factor for Homo sapiens to go out of Africa.

However, the Sahara problem among Homo sapiens and its possible way out. However, other climate studies show that there is a "wet" or "green" stage, during which more friendly corridors will be opened to form a path across the Sahara desert, and the time seems to coincide with the main dispersion stage of human beings leaving the Sahara desert. Sub-Saharan Africa (the determined wet period is about 50,000-C.45,000 years ago and C.120,000-C.10,000 years ago). However, a recent study shows that although the "wet" stage supported the early migration of Homo sapiens to the Levant and * * about 120000-90000 years ago, in the main migration period (about 55000 years ago), the Horn of Africa was actually very dry, arid and a little cold. Then, this may help to push the main wave. ?

Another example of climate affecting early human migration seems to have appeared earlier. About 870,000 years ago, the temperature dropped, and both North Africa and Eastern Europe became drier than before. This may lead to the migration of large herbivores to shelters in southern Europe, followed by early humans. At the same time, the trough in northern Italy was first opened, forming a channel that might migrate to southern France and other regions. This is very consistent with Heidelberg people entering Europe. In any case, it is a good strategy to follow large herbivores in the challenging migration process. The study of CE 20 16 shows that Homo erectus may do the same, and at the same time, it is close to flint sediments and avoids the areas where carnivores gather, at least in the early stage of their diffusion.

Regardless of the exact driving force or difficulties encountered by early human beings on the way, with the passage of time, adaptability has dominated, and human beings-from Homo erectus to Homo sapiens-have spread to the whole vast world.

blind zone

But there are obviously many loopholes in this story, and it is no harm to point out some blind spots that we must consider at this time. Generally speaking, the above date is only our best estimate based on the interpretation of the data collected so far. If we can grasp more evidence, we can find some areas that can enrich the following story.

For example, we only know a phalanx and three molars found in a cave in Siberia, and their DNA (their genomes were sequenced in 20 10), which seems to mean that they went all the way from there to Southeast Asia. In addition, they may cross with an unknown ancient human, which will obviously tell a story of their own. These mysterious human fossils are very popular and can be used to describe their lives and movements. Another mysterious species is flores people. How and when did they arrive in flores (did they use the ship in some way in the early days)? Who are their ancestors? More evidence is needed to reach an agreement.

Another place that makes researchers and scientists happy is America. There are still some conflicts about the exact route and time to go to America. Although the arrival date seems to be somewhere between 15000 years ago (there have been many quarrels going back and forth for thousands of years), a recent study (Holen 20 17) even thinks that early humans may have been in California before 130000 years ago; According to the hammers and anvils that the researchers saw, they thought they must have been made by humans (although there were no human fossils at the scene).

Obviously, more evidence is needed to cover the current story about the United States, but it forms a good example of what may happen to our current impression of early human immigrants with the emergence of new discoveries. Of course, we can't paint a complete and finished picture yet.