Författare Ämne: Tre vågfaser av människor till Amerika  (läst 2250 gånger)

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Tre vågfaser av människor till Amerika
« skrivet: september 03, 2010, 23:08 »
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Archaeological Support for the Three-Stage Expansion of Modern Humans across Northeastern Eurasia and into the Americas

Background
Understanding the dynamics of the human range expansion across northeastern Eurasia during the late Pleistocene is central to establishing empirical temporal constraints on the colonization of the Americas [1]. Opinions vary widely on how and when the Americas were colonized, with advocates supporting either a pre-[2] or post-[1], [3], [4], [5], [6] last glacial maximum (LGM) colonization, via either a land bridge across Beringia [3], [4], [5], a sea-faring Pacific Rim coastal route [1], [3], a trans-Arctic route [4], or a trans-Atlantic oceanic route [5]. Here we analyze a large sample of radiocarbon dates from the northeast Eurasian Upper Paleolithic to identify the origin of this expansion, and estimate the velocity of colonization wave as it moved across northern Eurasia and into the Americas.

Methodology/Principal Findings
We use diffusion models [6], [7] to quantify these dynamics. Our results show the expansion originated in the Altai region of southern Siberia ~46kBP , and from there expanded across northern Eurasia at an average velocity of 0.16 km per year. However, the movement of the colonizing wave was not continuous but underwent three distinct phases: 1) an initial expansion from 47-32k calBP; 2) a hiatus from ~32-16k calBP, and 3) a second expansion after the LGM ~16k calBP. These results provide archaeological support for the recently proposed three-stage model of the colonization of the Americas [8], [9]. Our results falsify the hypothesis of a pre-LGM terrestrial colonization of the Americas and we discuss the importance of these empirical results in the light of alternative models.

Conclusions/Significance
Our results demonstrate that the radiocarbon record of Upper Paleolithic northeastern Eurasia supports a post-LGM terrestrial colonization of the Americas falsifying the proposed pre-LGM terrestrial colonization of the Americas. We show that this expansion was not a simple process, but proceeded in three phases, consistent with genetic data, largely in response to the variable climatic conditions of late Pleistocene northeast Eurasia. Further, the constraints imposed by the spatiotemporal gradient in the empirical radiocarbon record across this entire region suggests that North America cannot have been colonized much before the existing Clovis radiocarbon record suggests.

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012472

Studien är Open Access så det är bara att börja läsa.

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SV: Tre vågfaser av människor till Amerika
« Svar #2 skrivet: oktober 01, 2010, 14:19 »
Vad för sorts tidsskrift är Cosmos? Har aldrig hört talas om den innan, en engelsk version av illustrerad vetenskap?

Får kolla om någon pressbyrå kanske har den så man kan ta sig en titt.

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SV: Tre vågfaser av människor till Amerika
« Svar #3 skrivet: september 04, 2011, 13:26 »
Sammanställning av litteratur som behandlar befolkningen av Amerika. Här talar man om två vågfaser ganska nära varandra i tiden.

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A Tale of Two Migrations: Reconciling Recent Biological and Archaeological Evidence for the Pleistocene Peopling of the Americas

This article synthesizes the 2000s-era “peopling of the Americas” data drawn from molecular biology, osteology, and archaeology. Collectively, they suggest that colonization proceeded in two pulses, both originating in western Beringia, and before that, south-central and southeastern Siberia. The first pulse occurred circa 16 k–15 k cal. B.P. by watercraft along the coast of Beringia and western North and South America. The second took place 1,000 years later and involved proto-Clovis hunter-gatherers who used the ice-free corridor as a conduit south. At least eight North American sites dating as far back as the Last Glacial Maximum suggest that the peopling picture may eventually need to change to accommodate an earlier than previously thought migration through the ice-free corridor. For now, the data are not strong enough to support this scenario, but they are tantalizingly close.

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SV: Tre vågfaser av människor till Amerika
« Svar #4 skrivet: september 12, 2011, 19:14 »
Dom slående argumenten är tydligen inte långt borta:

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Archeologists have discovered thousands of stone tools in Texas that are over 15,000 years old. The find is important because it is over 2,000 years older than the so-called Clovis culture, which had previously thought to be the first human culture in North America. As Texas A&M University anthropologist Michael Waters says, “This is almost like a baseball bat to the side of the head of the archaeological community to wake up and say, ‘hey, there are pre-Clovis people here, that we have to stop quibbling and we need to develop a new model for peopling of the Americas’.”


http://blogs.discovermagazine.com/80beats/2011/03/25/new-archeology-find-buries-theory-on-first-americans-re-opening-a-gaping-mystery/
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