The land bridge that emerges when sea level drops at the Strait of Bering has served as a corridor for animals to move between Eastern Asia and the Americas over the past 2 million years, and we assume that human beings used it to enter America coming from Asia around 20,000 years ago. There is an additional use for the land bridge across the strait as a place where humans diversified during a "standstill" there creating the unique Amerindian genetic patterns, and also as a refuge during the height of the ice age when glaciers blocked their entry into America.
I don't buy the standstill (see this 2014 post), but you can read about it here, and a critique here.
The first to suggest the idea of Asians entering America by foot was the Spanish Father José de Acosta in 1590 (Historia Natural de las Indias), when the existence of Bering Strait wasn't even known, he proposed that the "Indians" had reached America from Asia: "How did the first inhabitants of the Indies reach it… not by sailing the sea but by walking on land."
But when did this happen? According to a paper published in September 2025, not as early as we had suspected (Wanket, C., Kodama, S., Oppenheimer, J., Cocker, S., Steigerwald, E., Froese, D., Shapiro, B., Pico, T., & Farmer, J. (2025). Converging evidence constrains late pleistocene bering land bridge history. Quaternary Science Advances, 19, Article 100292. https://doi.org/10.1016/j.qsa.2025.100292.
The Strait of Bering and surrounding seabed is quite shallow, roughly 53 m deep nowadays (180 ft.), and it has emerged and been flooded as sea levels rise and fall. The main cause of sea level variation is global cooling and warming: when the world cools during the ice ages, snowfall accumulates producing vast ice fields across the northernmost and southernmost parts of the globe, the water in the ice comes from the sea, causing its level to drop. When the climate heats up (like it is doing nowadays -Global warming) the ice melts and sea levels rise: "Global average sea level has risen 8–9 inches (21–24 centimeters) since 1880. In 2023, global average sea level set a new record high—101.4 mm (3.99 inches) above 1993 levels." (https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level)
When the sea level is low, a dry area links Asia with America: The Beringian land bridge.
These sea level fluctuations imply that the Beringian land bridge or BLB formed many times over the past 2,000,000 years and formed during the cold spells at the peak (Maximum) of these Ice Ages, the most recent one was the Last Glacial Maximum or LGM. Warmer interglacial periods submerged that route and would have required navigating across a short stretch of sea between Asia and Alaska.
This paper finds that the evidence it analyzed "support the idea that the BLB was last exposed shortly before the LGM, over 30 kyr later than traditionally assumed."
This narrows the window of opportunity for the migration of modern humans into the New World to between 36,000 and 12,000 years ago, the last time that the BLB emerged.
And also ignores the fact that humans could have navigated across the ocean between Asia and Oceania to America at any time since the earliest Out Of Africa migrations of H. sapiens (~177-194.000 years ago - Source).
Older Bridges
But this is only the latest land bridge. There were many more in the past.
The Wisconsin glaciations (12 – 110 ky) were one of many that occurred during the last half million years. Other recent glacial events are the Illinoian (120-200 ky) and pre-Illinoian (300/380 – 455 ky). Regarding fauna migration, an ancestor of both black and brown bears colonized the Siberian steppe about 3.5 Ma., and shortly after. the black bears migrated into America across Beringia. They were followed by the brown bears 300 ky. The cave lion ancestor of the American lion (puma) entered America through Beringia during the next-to-last (Illinoian) period. In an inverse path across Beringia, horses, who originated in America, dispersed across Eurasia 1 Ma., and woolly mammoths from the New World colonized Eurasia 60 ky. Could this mean that even earlier arrival dates for humans are possible?
Yes! The Bering Land Bridge formed many times. The problem lies in the timing of an Out of Asia event. Current evidence suggests humans reached Northeastern Asia some 40,000 years ago, so they could have only entered America during the LGM. But, other hominins have lived in Asia over the past 1.8 million years, they could have moved into America using an ancient BLB.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2025 by Austin Whittall ©
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