Robert Kirkconnell said:
The meteor/comet connection is a new one to me. I will need to check into it, because I have taken several advanced environmental science courses and never ran into it. Doesn't mean it doesn't exist, just don't know anything about it. I will be writing about environmental issues in the future, and this is interesting. Thanks.
It's a subject that, for the most part, has been much ignored. Laura has written extensively about it, both prior to and in her latest book
Comets and The Horns of Moses (which focuses on the history of comet-Earth interactions and also - among other things - how these have given rise to religions, belief systems, and cultural practices). I'll give a very brief and sketchy overview of the general idea, and then a link to read up on it and find citations of the research it is based upon:
Much of the research comes from Victor Clube and Bill Napier, who traced a number of contemporary comet streams to the break-up of a giant comet long ago - following which its more dangerous streams have periodically collided with the Earth and caused major catastrophes.
Among many other sources often referred to are Firestone, West and Warwick-Smith. The Nemesis Hypothesis also plays its part - the idea here is that of a twin sun (brown dwarf in a very eccentric orbit) which periodically travels through the Oort Cloud and hurls comets into the inner solar system - though the basic idea does not depend on this. (There are other possible explanations for the periodic entry of new comets into the inner solar system.)
Evidence from hard sciences point to common (occuring a few thousand years apart), very widespread disasters that often destroy several major civilizations at once. Mainstream archaeology (and the specializations dealing with different civilizations), on the other hand, is generally stuck in a uniformitarian dogma, wherein no sudden, abrupt, wide-ranging events can ever occur. Hard evidence from geology, dendrochronology, and carbon dating is routinely dismissed within mainstream history.
There is a also the viral question, with research pointing to comets as a source of microorganisms that survive entry into the atmosphere. When it comes to several major plagues thoughout history, comets are at present the only known explanation for how a new viral plague could have spread to several places faster than people and animals can travel: the pathogen (or new viral DNA soon combining and giving rise to the disease) came down through the atmosphere.
Apart from the books, there's a series of articles
on SOTT about the (very wide and general) subject. The following quote from astronomer Victor Clube, from a report commissioned by the U.S. Air Force, gives the big picture - keeping in mind that today we have the "War on Terror" instead of the "Cold War":
"We do not need the celestial threat to disguise Cold War intentions; rather we need the Cold War to disguise celestial intentions!"
You may also want to look into the American Meteor Society's reported events, which show an exponential increase in incoming fireballs and atmospheric explosions since 2005. According to Clube's models, we have entered a "dangerous time", and the current evidence appears to fit this.