Windows for the crossing of the Beringia landbridge into America from Asia have existed many times before the latest one (at the end of the last Ice Age) during which supposedly modern humans finally entered America around 16,000 years ago.
Animals have crossed to and fro between Asia and America (horses, black bears, caribou and camels went west into Asia while bison, mammoths, moose and elk moved east into America) during the last 8 million years. So why couldn't our more distant human relatives (H. habilis, H. erectus, Neanderthal or Denisovan) do the same thing?
The following chart from History of Earth's Climate 5. - Cenozoic II - Pleistocene at www.dandebat.dk, shows how the sea level rose and dropped over tha last 800,000 years. As you can see, during the interglacial periods -like the current one- ice melted and the sea levels rose (zero meter is the present sea level), but when the ice caps grew during the ice ages and glaciers advanced, water was moved from sea to continental ice sheets and therefore sea level dropped by over 120 meters or approx. 360 feet. More than enough to dry out Beringia and allow the land bridge to link America and Asia.
The red arrows show the dates these bridges formed: 140, 340, 630 and 720 thousand years ago. And the blue arrow shows the most recent event, the that is the "accepted" date for the entry of humans into America.
Actually the arrows point at the "lowest" sea levels but to cross Beringia only a drop of 60 meters is needed so there were plenty more "windows" and these lasted for quite a long time (see this map for an undersea level contour of Beringia).
The fact is that humans existed 140 kya, and perhaps even 340 kya. Neanderthals lived between 630 and 140 kya. Densiovans are a mystery but we may assume the same dates as those of the Neanderthals. Homo erectus on any date earlier than 340 kya.
So we should consider these dates as "windows of opportunity" for the first humans to reach America.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2018 by Austin Whittall ©
Austin,
ReplyDeleteIn light of the recent discoveries in the phillipines, it might be time to re-approach, not only the when, also the how and why, humans made the journey into the new world.
We might have to consider warm periods with high ocean levels as well, as the lessened sea ice and milder climate would have made it easier for water oriented people to move around
Dear Austin, at last a blog post discussing possible dates for the peopling of the Americas!
ReplyDeleteHowever, if one looks at the research done over the years, there is quite a lot of evidence that multiple Beringian land bridges have existed in the last 2 millennia. I did a post much like yours (found at this link: http://thefuzzysasquatch.blogspot.com/2016/01/the-peopling-of-americas-ii-bering-land.html?m=1 ) that shows there have been a possible 39 land bridges if you take a 50m drop in sea level as the minimum for their formation. Let me know what you think. NeilB
Great data.
ReplyDeleteCasually, 140 k years is similar to Cerutti... and 250 k is similar to Hueyatlaco site age.
ReplyDelete