Recent African origin of modern humans

The recent African origin of modern humans, also called the Out of Africa theory, explains where we all come from today. It says that people living outside of Africa are mainly descended from a group of modern humans, called Homo sapiens, who left Africa about 70,000 to 50,000 years ago. This idea is the most commonly accepted way scientists think about how humans spread around the world.

Before this group left Africa, other early human relatives like Homo erectus and Homo neanderthalensis had already moved out of Africa. But the recent African origin model suggests that modern humans developed in Africa between 300,000 and 200,000 years ago. From there, they moved out in several waves, but the one that led to most of today’s non-African people happened around 70,000 to 50,000 years ago. These humans traveled along the coast of Asia and reached Australia by about 65,000 to 50,000 years ago.

More recent studies in population genetics have shown that modern humans mixed with older human groups in Eurasia, Oceania, and Africa. This means that today’s people are mostly from those early Homo sapiens who left Africa, but also have some connection to older human types that lived in those areas.

Proposed waves

Further information: Early expansions of hominins out of Africa and Skhul and Qafzeh hominins

The idea of "recent African origin," also called "Out of Africa II," talks about how modern humans (Homo sapiens) moved out of Africa after they first appeared between 300,000 to 200,000 years ago. This is different from "Out of Africa I," which was about earlier human relatives moving out of Africa long before that.

Since the year 2000, scientists have found more evidence that shows these migrations happened in several waves over a long time. By 2010, two main paths were accepted for how early modern humans left Africa: a "Northern Route" through the Nile Valley and Sinai, and a "Southern Route" across the Bab-el-Mandeb strait.

Some studies suggest that humans might have left Africa as early as 270,000 years ago. Other discoveries, like a skull fragment from Apidima Cave in Greece that is about 210,000 years old, and a jawbone from Misliya cave dated to around 185,000 years ago, also point to earlier migrations. Stone tools found in Jebel Faya dating back to 127,000 years ago show humans may have moved to Arabia between 150,000 and 130,000 years ago.

The biggest movement out of Africa happened around 50,000–70,000 years ago, following the southern coast of Asia. This group reached Australia by about 65,000–50,000 years ago. Western Asia was settled again around 50,000 years ago, and Europe was populated from there starting around 43,000 years ago.

Northern Route dispersal

Further information: Skhul and Qafzeh hominins

See also: Levantine corridor

About 135,000 years ago, big dry periods in tropical Africa pushed people toward the coast and across to other continents.

Scientists have found very old fossils of early humans in Qafzeh and Es-Skhul Caves in Israel, dated between 80,000 and 120,000 years ago. These early humans either disappeared or went back to Africa around 70,000 to 80,000 years ago, maybe replaced by Neanderthals moving south from colder parts of Europe.

In 2011, stone tools found in the United Arab Emirates at the Faya-1 site in Mleiha, Sharjah showed that modern humans lived there at least 125,000 years ago. This helped scientists understand that northern Africa was an important path for humans leaving Africa.

In Oman, stone tools found in 2011 suggest humans lived there about 106,000 years ago, showing a different Stone Age tool style in southern Arabia.

Studies show that Neanderthals and early humans living outside Africa around 100,000 years ago shared genes, meaning they met and had children together long before scientists thought.

Southern Route dispersal

Main article: Southern Dispersal

Further information: List of first human settlements

Coastal route

Around 50,000 to 70,000 years ago, a small group of humans left East Africa and moved into the Near East. This group, which may have been as small as 150 to 1,000 people, crossed the Red Sea and traveled along the coast of Arabia and the Persian Plateau to reach India. This area was likely the first major place where these humans settled. They continued along the southern coast of Asia and reached Australia by about 50,000 years ago.

Today, the Red Sea is about 20 kilometres wide, but 50,000 years ago, it was much narrower due to lower sea levels. This made it easier for humans to cross using simple rafts, and there may have been islands along the way to help them. Old shell piles found in Eritrea show that these early humans ate seafood from the beach.

Toba eruption

Main article: Toba catastrophe theory

The timing of this movement of humans is not fully agreed upon. It may have happened either before or after a huge volcanic eruption of Lake Toba in Indonesia, which occurred between 69,000 and 77,000 years ago. Some clues from old stone tools in India suggest humans may have moved out of Africa before the eruption, while other evidence points to humans leaving a few thousand years after the eruption. Recent research suggests the migration might have happened between 90,000 and 130,000 years ago, but many still believe it was around 50,000 to 75,000 years ago.

West Asia

Fossils found in Israel that are 80,000 to 120,000 years old show that humans were in this area long ago. However, there are no fossils of modern humans in the Levant until about 54,700 years ago. This gap suggests that modern humans may have been outcompeted by other human groups, like Neanderthals, until around 55,000 years ago. Climate conditions also favored the coastal route for human movement out of Africa rather than the northern route.

Oceania

Fossils from Lake Mungo in Australia have been dated to about 42,000 years ago. Other sites, like Madjedbebe, may be as old as 65,000 years, though some researchers think the oldest layers are about 50,000 years old.

East and Southeast Asia

In China, one of the oldest known modern human remains is called the Liujiang man, who lived around 67,000 years ago. Another important find is the Tianyuan man, who lived between 38,000 and 42,000 years ago. Studies show that Tianyuan man is related to many present-day Asians and Native Americans.

Americas

Studies show that Native Americans come from a single group that split from people in Mainland Southeast Asia around 36,000 years ago. This group later split into the ancestors of all Indigenous peoples of the Americas around 16,000 years ago. An ancient sample from Idaho dated to 16,000 years ago shows strong ties to modern East Asians and people from Japan during the Jōmon period.

Europe

One theory suggests that a group of humans traveled north along the Nile River from East Africa and entered Europe through the Sinai peninsula. This group split, with some moving into Europe and others heading further east into Asia. By 45,000 years ago, modern humans had reached northwestern Europe.

Genetic reconstruction

Mitochondrial haplogroups

Within Africa

Further information: Genetic history of Africa

See also: Most recent common ancestor, Archaeogenetics, and Human mitochondrial DNA haplogroup

One important family of genes comes from a mother called Mitochondrial Eve. A special group of these genes, called L0, is mostly found in the San people of Southern Africa and the Sandawe people of East Africa. These groups separated early from other humans and stayed mostly separate since then. Other groups of genes, called L1, L2, and L3, also mostly stay in Africa. The genes M and N, which are found in people outside Africa, come from L3. L3 is about 70,000 years old, and M and N are about 65,000 to 55,000 years old. Scientists are still discussing how these genes relate to human history.

Only one group of genes, called L3, has descendants found outside Africa. If people had left Africa more than once, we would expect to see more groups of genes from Africa in people around the world. The descendants of L3, called M and N, are found in very small numbers in Africa. One idea is that these genes changed in East Africa just before people left and became more common because of this change. Another idea is that they changed after people left Africa.

Southern Route and haplogroups M and N

Results from genes studied in Orang Asli people, who live in Malaysia, show that genes M and N share features with very old African groups from about 85,000 years ago. They also share features with groups in coastal Southeast Asia, like in Australasia and the Indian subcontinent, and all through Asia. These groups split from their African ancestors about 65,000 years ago. This coastal route would have happened before people moved through the Levant about 45,000 years ago. This helps explain why gene group N is common in Europe, but M is not found there. Evidence for this coastal journey might have been lost when sea levels rose during a time called the Holocene. Another idea is that early Europeans had both M and N, but lost M by chance.

The group that crossed the Red Sea moved along the coast around Arabia and Persia to reach India. Gene group M is common along the southern coast of Pakistan and India, and it is most diverse in India. Sixty percent of Indians have M, as do people from the Andaman Islands, who are thought to be some of the earliest people in Asia because they lived apart from others for a long time. Since M is common in people from New Guinea and the Andaman Islands, who have dark skin and Afro-textured hair, some think they all came from the same group of migrants who left Africa across the Red Sea about 60,000 years ago. M becomes more common as you move east from Arabia to India. In eastern India, M is three times more common than N. Moving into Southeast Asia, N becomes more common again. M is common in East Asia, but among Indigenous Australians, N is more common. This mix of M and N from Europe to Australia can be explained by chance events and changes in small groups of people.

Autosomal DNA

Further information: Human genetic variation

A study from 2002 looked at people from Africa, Europe, and Asia. It found that Africans have more genetic variety than people from Eurasia, and that Eurasian variety is mostly a smaller part of African variety. This supports the idea that humans originated in Africa. A later study in 2009 found evidence that people outside Africa faced new challenges, leading to changes in their genes. For example, genes related to skin color changed in different areas. This shows that people adapted to new places as they left Africa.

Pathogen DNA

Another way to study human history is by looking at a virus called the JC virus, which most humans carry. This virus is passed from parents to children and changes very little, so it can show how humans moved. However, this method does not work well for studying how people left Africa, because the virus types from Africa are not the oldest. This makes some scientists think that either the oldest African virus type died out, or that people got the virus after they left Africa.

Admixture of archaic and modern humans

Main article: Interbreeding between archaic and modern humans

In the 2010s, scientists found evidence that modern humans mixed with older human types after leaving Africa. This mixing happened mostly with Neanderthals in all people except those from Sub-Saharan Africa, but also with Denisova hominins in some areas of Australasia. The amount of Neanderthal mixing in Europeans and Asians is about 2–3%.

In 2011, scientists found that some hunter-gatherer groups in Africa, like the Biaka Pygmies and San, also mixed with older human types that split from modern humans about 700,000 years ago. This mixing was about 2%. Even earlier mixing, from 1.2 to 1.3 million years ago, was found in Pygmies, Hadza, and Sandawe people in 2012.

A study in 2020 found that people from West Africa, like the Yoruba and Mende, have between 2% and 19% of their DNA from an unknown older human type that lived before Neanderthals and Denisovans.

Stone tools

Further information: Aterian, Baradostian, and Microlith

Besides studying genes, scientists also look at old stone tools to understand how people moved. Small stone tools from South Asia can be dated to about 35,000 years ago. These tools might have been made because of changes in the environment or because there were more people.

History of the theory

Classical paleoanthropology

Further information: Timeline of human evolution and Paleoanthropology § History of paleoanthropology

Charles Darwin studied African apes and thought humans might have come from Africa. Another scientist, Thomas Huxley, agreed. But a German biologist named Ernst Haeckel thought humans were more related to apes in Southeast Asia.

In 1871, there were very few ancient human fossils known. Later, scientists found many fossils in Africa. This supported Darwin’s idea that humans began in Africa.

Multiregional origin hypothesis

Main article: Multiregional origin of modern humans

Some scientists believed humans evolved everywhere at once, not just in Africa. This idea was suggested in the 1980s. But most scientists now think humans began in Africa and then spread out.

Mitochondrial analyses

Further information: Mitochondrial Eve

In the 1980s, scientists studied DNA from cells’ power centers to learn about human history. They found that all people today come from one woman who lived in Africa a long time ago.

Y-chromosome analyses

Further information: Y-chromosomal Adam

Scientists also studied DNA from men’s cells to learn about human history. They found that all men today come from one man who lived in Africa a long time ago.