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The Straight Facts
The Bering Strait is located between the coasts of Siberia and Alaska with a max depth 164 feet, and a length of about fifty miles (Britannica, 2019). Not very feasible for a human to be able to cross it without a boat correct? Well, around fifteen thousand years ago this Strait most likely served as a bridge for the early humans to first colonize North America. When the most recent Ice Age lowered sea levels, these early humans simply just had to walk from what is known today as Siberia in order to reach North America (National Geographic 2021). The water levels decreased so drastically, that all 164 feet of water that is seen there today, once was not, and gave an access of passage to our ancestors. This Land Bridge did not just serve as a passageway for humans however. It also led different animals such as mammoths, muskox, and lemmings across to Alaska (PBS, 2021). These animals actually led the early humans onto the land bridge without them even knowing. Our ancestors were simply just following the food in order to stay alive, and they followed it all the way to the new world.
Where it All Started
Around four million years ago bipedalism hit the first ape-like humans that originated in the continent of Africa. From there, humans moved north and began populating what is known today as Asia and Europe. However, our ancestors weren't able to move any further from there because of the massive ocean that encompassed all of the continent. So what was the thing that brought humans to the Bering Strait just at the right time? The one thing that modern day humans share with the earliest form of man four million years ago is the occupation of a large brain (Smithsonian, 2021). This brain is what helped to put humans on the top of the food chain, and boost our evolutionary process. This special brain of ours helped us to think outside of the box; such as using tools, communication, forms of expression, art, and cultural diversity (Smithsonian, 2021). It was the brain that allowed humans to colonize the rest of the new world. That brought early man to the Bering Strait right at the time when it could only be crossed. Of course, the early humans were just following the food, but it was their brain that told them where to hunt, and where the food will be.
"Bering Land Bridge", by National Geographic, is licensed under the Public Domain.
"Watch Our Planet Evolve" by Metrocosm, is licensed under Public Domain
"Pleistocene Epoch", by Bluff Park Back Porch, Licensed by Public Domain
How The Land Bridge Formed
The Pleistocene Epoch was era in time that began around 2.6 million years ago and ended around 11,700 years ago (Zimmerman, 2017). During this epoch, there were likely four different Ice ages that occurred with the most recent one ending not too long ago. During the most recent Ice age, sheets of ice would cover all of Antarctica, large parts of Europe, North America, South America, and small parts of Asia. In North America the sheets stretched over Canada and the Northern United States (Zimmerman 2017). Over a long period of time these glaciers and ice sheets would thaw and refreeze over the course of many cycles. When these glaciers formed however, They absorbed a large volume of sea water which could lower sea levels up to 300 feet. The water level ended up dropping so drastically that the sea floor in the Bering Strait was exposed. This formed what is known as a land bridge which allowed early humans and animals to cross for a limited amount of time. Climate change at the back end of the most recent Ice age caused glaciers to melt. Resulting in the bridge slowly being re-submerged again under water. It wasn’t until six thousand years ago that the Bering Strait retained similar water levels to the ones seen today (Crow Canyon Archeological Center, 2014).
The Migration in North America
Humans may have populated the Americas in small numbers over very long periods of time. Some of these small groups would have survived, and some of them didn’t. It’s entirely possible that some groups genetic traits might be different from others, which would either help them or harm them when it came to things like disease (Dixon, 2001). Once in America, species that had never seen such intelligent life before were not used to the idea of human hunters. Therefore, food was not hard to come by as hunting was made child's play. It’s also theorized that these early humans could have possibly hunted certain species to extinction because it was not a difficult task. Some archeologists think that unlike modern foragers who are geographically based, early humans may have been more intent on knowledge of animal behavior and technology. This quite possibly could have allowed them to move from region to region exploring various species. This is what likely caused a rapid colonization (Dixon, 2001). It is believed that humans might have been able to colonize both North and South America in a matter of 1,000 years. During that time the early humans could have killed off large Pleistocene mammals and rapidly looked for more food. While others theorize that it was the cause of climate change and human predators to encourage early humans to migrate extremely quickly (Dixon, 2001).
"Ancient Humans Hunted Big Mammals to Extinction", by NPR, Licensed by Public Domain
Other Possible Theories
Some archeologists theorize that humans could have possibly been on both sides of the land bridge already when it was formed. Some of the archeological evidence found by scientists could pose key flaws in the theory of the Bering Strait Land Bridge. A new theory that has been recently surfacing is that as the end of the last Ice age came about, the coastline of British Columbia and Southeastern Alaska were becoming ice-free as far back as 18,000 years ago (Montaigne, 2020). Archeologists from a study in British Columbia noted that it was possible for humans to have traveled by boat down the shorelines after the ice melted. After the last Ice age, sea levels rose dramatically. However, after that extreme weight of the glaciers being removed from the earth's crust, it might have caused a bounce back effect. This would mean that even though the seas rose, the land bouncing back would almost entirely cancel it out. Making it entirely possible for the shoreline from 14,000 years ago to look almost the same as the shoreline today (Montaigne, 2020). From paddling down the coast the early humans could have encountered the Columbia River. Which would have been the first break in the ice allowing the early humans to enter North America (Davis, 2020).
Understanding the Theory
Pangea is defined as “ a supercontinent that incorporated almost all the landmasses on Earth. Pangea was surrounded by a global ocean called Panthalassa”. It is believed that when the big bang occurred, it split Pangea into the seven continents known today. Now, this has had a great impact on evolution. The biggest evolutionary change was the continental drift of the Earth’s land. Each species had a new location, some were split up, and there were major climate changes for some locations of Pangea after they were separated into continents. When continents break up one group of species is split up from another and both species are forced to evolve separately. The thought process behind the species dividing into two both physically and genetically can be exemplified with the Bonobo and the Chimpanzee of today. Bonobos share 99.6 percent of their DNA with Chimpanzees which makes them very similar to each other genetically even though their species split apart in Africa over one million years ago. Bonobos are only found in The Democratic Republic of Congo and researchers do not believe they have interbred with Chimpanzees since the species split. The researchers believe that the species split up due to the forming of the Congo River. These researchers also believe that the Congo River also acted as a barrier to prevent these species from interacting. This is an instance similar to how the breakup of Pangea affected the evolution of a variety of species.
Essentially, the effect that the breakup of Pangea had on the evolution of many species was different for each individual species. However, the fact of the matter is, it split countless species up and put them into a new climate where they would need to adapt and evolve to new circumstances.
References
Britannica. (2017). Bering Strait. Encyclopædia Britannica. Retrieved December 9, 2021, from
https://www.britannica.com/place/Bering-Strait.
CrowCanyon. (2014). The bering land bridge: Peoples of mesa verde. The Bering Land Bridge | Peoples of Mesa Verde. Retrieved
December 9, 2021, from
https://www.crowcanyon.org/educationproducts/peoples_mesa_verde/paleoindian_bering_land_bridge.asp#:~:text=It%20was%20expose d%20when%20the,animals%20and%20people%20could%20traverse.
Dixon, E. J. (2000, December 18). Human colonization of the Americas: Timing, technology and Process. Quaternary Science Reviews.
Retrieved December 3, 2021, from https://www.sciencedirect.com/science/article/pii/S0277379100001165.
Gibbons, A. (2012, June 13). Bonobos join chimps as closest human relatives. Science.org. Retrieved November 1, 2022, from https://www.science.org/content/article/bonobos-join-chimps-closest-human-relatives
Geographic Society, N. (2013, April 18). Bering Land Bridge. National Geographic Society. Retrieved December 5, 2021, from
https://www.nationalgeographic.org/photo/bering-land-bridge/.
McIntyre, S. R., Lineweaver, C., Groves, C. P., & Chopra, A. (2017, June 7). Geology and biology agree on Pangaea supercontinent breakup dates. ANU. Retrieved November 1, 2022, from https://www.anu.edu.au/news/all-news/geology-and-biology-agree-on-pangaea-supercontinent-breakup-dates
Montaigne, S. (2020, January 1). The story of how humans came to the Americas is constantly evolving. Smithsonian.com. Retrieved
December 4, 2021, from https://www.smithsonianmag.com/science-nature/how-humans-came-to-americas-180973739/.
Scoville, H. (2019, July 19). Tectonic plates' effect on evolution. ThoughtCo. Retrieved November 1, 2022, from https://www.thoughtco.com/how-earth-changes-affect-evolution-1224552
The Smithsonian. (2020, October 27). Introduction to human evolution. The Smithsonian Institution's Human Origins Program.
Retrieved December 2, 2021, from https://humanorigins.si.edu/education/introduction-human-evolution.
Travel Guide, P. B. S. (2015). PBS arctic journeys | travel guide | history and culture. PBS. Retrieved December 3, 2021, from
http://www.pbs.org/beringlandbridge/guide/history.html.
Zimmermann, K. A. (2017, August 29). Pleistocene epoch: Facts about the last ice age. LiveScience. Retrieved December 2, 2021, from
https://www.livescience.com/40311-pleistocene-epoch.html.
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Wikipedia, 2021, Bering Strait. https://upload.wikimedia.org/wikipedia/commons/1/16/Bering_Strait.jpeg
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