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My very latest thoughts:
The Amazonian megafuana could have been due to the proposed event of 40,000 BP. Speculation has existed for a long time that a massive body close encounter has occurred in the Earth's recent past, possibly in the order of a few moon diameters from the Earth's surface, creating a flexure of the lithosphere. A temporarily disrupted magnetic field would allow much more cosmic rays and solar radiation to reach the surface during this time. Three main pieces of evidence point to this conclusion:
(i) The frozen Siberian mammoths in near standing positions with buttercups in their mouths, dated to around 40,000 BP. This would fit with the sudden liquefaction and elevation of the landmass into freezing air temperatures above.
(ii) The DNA analysis of the first human colonisation of the Australian continent all converge on the date of 40,000 BP. This fits with the hypothesis of a temporary land bridge between S.E Asia and the Australian land mass, crossing the mammalian/marsupial Wallace line.
(iii) The enormous guano mud flow in the high Niah Cave complex of Borneo dated to around 40,000 BP has been attributed to an inexpicable sudden influx of a large volume of water. This is consistent with a mega tsunami which would have been associated with the flexing of the Earth's crust due to the gravitational close encounter of the celestial body.
Take note that the other non-DNA dating techniques used would be adversly affected by a dramatic change in the Earth's magnetic field due to this proposed event. This should cause the previously given dates earlier than 40,000 BP to be treated with renewed suspicion and require a complete re-evaluation of their reliability.