The sea level in the Bering Strait today is hundreds of feet higher than it was when the Bering Land Bridge connected Siberia and Alaska.

Anthropology: Out of Africa Theory and Early Human Migration

Ever since the beginning of time, people have explored and traveled, even with the obstacles, the danger, and risk of illness and death. Still, our ancestors traveled and brought us to where we are today. But why? Let’s start from what we know as the Out of Africa Theory!

Out of Africa Theory

An article New Research Confirms ‘Out Of Africa’ Theory Of Human Evolution “states that the research confirms the “Out Of Africa” hypothesis that all modern humans stem from a single group of Homo sapiens who emigrated from Africa 2,000 generations ago and spread throughout Eurasia over thousands of years. These settlers replaced other early humans (such as Neanderthals), rather than interbreeding with them.”

However a Blog at the Graduate School of the Arts and Sciences at Harvard University talks about a recent finding in forensic anthropology that may actually contradict the Out of Africa hypothesis. Israel Hershkovitz of Tel Aviv University discovered the artefactual jaw fragment. The fossil is evidence that humans were exploring regions outside Africa much earlier than thought, about 55,000 years ago. This finding might help scientists figure out the motivation behind the migration depending on the timeline.

Homo sapiens jaw bone in Israel, however, has been dated between 177,000 and 194,000 years old. Image credit: NPR

It makes me wonder why there was a sudden migration back then? Was there civil unrest? Did they run out of resources? The theorized migration patterns are also neat to look at.

Map of Out of Africa Theory Credit: @Prince8888

It’s very interesting to see how people happened to get across the Ocean to North America and in such cold weather and terrain! They did this via the Bering Strait.

View of the Bering straight from space.
Credit: Wikipedia

Further more, they found a 12,000 year old skeleton in an underwater Mexican cave that shows that her mitochondrial DNA is from an Asian lineage from an article Perfectly-Preserved 12,000-Year-Old Skeleton Proves Bering Strait Theory that supports the Bering Strait Theory.

The sea level in the Bering Strait today is hundreds of feet higher than it was when the Bering Land Bridge connected Siberia and Alaska.
Credit: Anne Morkill, USFWS

“Approximately 11 percent of Native Americans exhibit this genetic lineage,” says Deborah Bolnick, a co-author of the paper reporting the findings, which appeared Thursday in the journal Science.

This favors the model of migration from Asia across the Bering Strait to North America called the Land Bridge Theory. In the 1800s, American scientists and archeologists started investigating archeological sites on the east coast of the United States, across to the west coast. They found that the origin was not from North America but from another place. Not until the mid-1920s did scientists come to know how people got to North America.

We can see that today’s development of civilization can be attributed to migration and exploration. Travel, migration, exploration all lead to diversity not only genetically but economically as well. An article The ‘Out of Africa’ Hypothesis, Human Genetic Diversity, and Comparative Economic Development argues that “deep-rooted factors, determined tens of thousands of years ago, have had a significant effect on the course of economic development from the dawn of human civilization to the contemporary era. It advances and empirically establishes the hypothesis that, in the course of the exodus of Homo sapiens out of Africa, variation in migratory distance from the cradle of humankind in East Africa to various settlements across the globe affected genetic diversity and has had a long-lasting hump-shaped effect on the pattern of comparative economic development that is not captured by geographical, institutional, and cultural factors.”

Looking back at our history, we can see why exploration and travel are the fundamental building blocks of human diversity and advancement.

Key points on the “Out of Africa” Theory

Here are some key facts I found from

  • The “Out of Africa” theory (hypothesis) states that all modern humans stem from a single group of Homo sapiens who came from Africa.
  • The theory suggests that all modern non-African populations descended from the populations of homo sapiens that left Africa after their development in the Horn of Africa between 300,000 and 200,000 years ago.
  • Unlike other theories, the “Out of Africa” theory suggests a single origin of homo-sapiens – the Horn of Africa, as seen in the picture to the right.
  • The theory suggests a few waves of dispersal by humans.
  • These waves of migration steadily occurred throughout the world for tens of thousands of years, and eventually became the human civilization.
  • Scientists studying this theory determined that there was less genetic variation among the populations the farther the migration was from Africa. This was due to population drops the more humans spread out.
  • This determination was a result of researching genetic diversity in 53 human populations across the world.
  • This population drop was likely due to difficulties surviving, limited resources, or lack of adaptability in differing climates.
  • The “Out of Africa” theory also takes into consideration the variations in the size and shape of skulls found across the world. Of the 6,000+ skulls examined, scientists concluded that those from populations the farthest from Africa had the least variety.
  • Scientists and researchers have been collaborating around the world for many years to piece together evidence and information to establish a global understanding of the “Out of Africa” theory. This collaboration continues to this day.

Scientific Research Method involved in the Out of Africa Theory

Many advancements in technology have allowed scientists to trace the origin of the modern human. Using Genetic testing has given scientists who study paleoanthropology enough clues to how we are related to ancient hominids, where humans came from, and which routes they took to migrate and spread.

Mitochondrial DNA and Y Chromosome

Using genetic information from mitochondrial DNA and Y chromosomes. Because mitochondrial DNA isn’t stored in the nucleus, genes in mitochondria are not subject to natural selection like DNA from the nucleus. Therefore, there are many more genetic mutations that occur in mitochondrial DNA than in nucleus DNA and this is useful in constructing a genetic map for studying genealogy. Furthermore, the mitochondrial DNA is inherited from the mother and does not involve a recombination process with the father’s DNA. In this way, genetics can be traced back using maternal lines. In the same manner, geneticists can find paternal genetic genealogy through examining Y chromosomes do not recombine with another chromosome. Geneticists are able to easily study one’s ancestry by analyzing mutations found in this DNA and can obtain these samples simply by taking a swab from the inside of one’s mouth.

Archaeological Approach

Looking at the archaeological approach and using artifacts, fossils, bones, or tools also provides conclusive information. Scientists are able to use radio carbon dating, geological dating. The only caveat is that there can be errors in dating with this process.

Geological data is also a great source to map out human migration patterns. For example sea level, desertification, volcanic eruptions, Ice Age, give us insight into the reason of migration. Climate change is a huge issue nowadays but think about the past when there weren’t as many resources to travel. Studying this data we are able to theorize how humans migrated.

Mitochondrial Eve

 Charles Darwin was probably the first scientist to come up with the Out of Africa Theory. In his book, The Descent of Man in 1871 he proposes that gorillas and chimpanzees, species similar to humans, lived in Africa, ancestors of Human beings probably came from Africa as well. None of his theories could be proved because scientific methods were not advanced enough. It wasn’t until late 20th century when Out of Africa theory was supported with genetic evidence and excavated sources.

Richard Leaky found the two skulls and various bones in Ethiopia’s Omo River Valley in 1967. They were named Omo I and classified as Homo sapiens since they were very similar to modern human, albeit in more primitive forms. Recent studies determined Omo I lived about 195,000 years ago, which is the oldest date of modern human’s fossil ever discovered. This discovery greatly raised the credibility of Out of Africa theory and specified the origin of modern humans as east Africa.

Many genetic analyses also support Out of Africa theory. In an 1987 article of magazine Nature by Rebecca Cann et al. show the result of mitochondrial DNAs analyses of 147 people and concluded that all mitochondrial DNAs stem from one woman, named Mitochondrial Eve, who supposedly lived about 200,000 years ago in Africa. This conclusion is supported because most various and complicated lineage of Mitochondrial DNAs are found in Africa.

The genetic diversity in Africa is important evidence that Homo Sapiens originated from Africa. Many new groups have been progressively added. An example comes from a 2007 study, scientists took genetic samples from modern Aborigines and Asian population, and traced their family tree through their mitochondrial DNA and Y chromosome DNA. The findings were remarkable in that they found that Australians are all descended from humans who migrated from Africa to Asia between 50,000 and 70,000.

Finally in 2008, magazine Nature put a paper about the most detailed analysis on genetic diversity as Geneticists analyzed genes from 29 groups of people from all over the world and concluded that Homo sapiens spread from East Africa.

Significance in Anthropology and Technology

Why is it important to learn about the migratory patterns of the past? Learning about past human migratory patterns can help us understand geography and predict future trends in human migration. For example there have been talks about building a tunnel under the Bering Strait for a magnetic levitation train that can provide travel between the US and Russia within 15 to 20 minutes.

Advanced Tunnel Model using Magnetic Levitation trains for underground tunnel under the Bering Strait

From the US the Bering Tunnel would begin at Cape Prince of Wales in Alaska and on the Russian side it would include the microdistrict of Ozyorny, located 8 miles (13 km) to the North of the Russian town of Egvekinot– which is a seaport on Kresta Bay. From there the railway would go to the cities of BilibinoZyrankaUst-Nera and finally from there to Yakutsk. There it would connect to the existing Baikal-Amur Mainline and the Trans-Siberian Railway systems. China and other Asian and European countries would all be accessible.

Studying the past human behavior and migratory patterns can help us project the future of transportation. With advancements in technology, humans can travel much more quickly, efficiently, and safely adding to cultural hybridization and spread, similar to what our ancestors achieved.

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