Regarding the 12,000+ year old impact not mentioned by the Washington Post, some scientists think that much of the impact hit in the now Chicago area.

What is curious is that worldwide there is evidence of 12,000 year old impact exctictions even in Asia and the middle east. The civilization that predated the ancient Egyptians was lost with only a few remnants of legends of the Yeptepi people remained when Pharoic times began.
Also DNA tracing the X chromosme of mothers indicate that a cinch point exists 12,500 years ago when the human species had an incredibly small gene pool. So small in fact that human extinction may have been overcome by sheer luck.

Perhaps the theory that man was respondisble for the extinction of Mammoths, Sabre toothed tigers and a myriad of other creatures was bogus. By Occams Razor alone the impact theory seems best.