Comets And The Bronze Age Collapse
http://abob.libs.uga.edu/bobk/bronze.html
Earth has been periodically pelleted with comet fragments throughout the Holocene period. The evidence for the break-up of a large (> 50 km), short period (approximately 3.3 years), Earth-orbit-crossing comet is substantial and should be considered as hard as anything a trowel might turn up. What astronomical information cannot convey is the actual effect these periodic bombardment episodes had on human culture; only further digging and sifting will illuminate that aspect.
There's also a part two to this article:
A Nickel Pickle:
There is though, another agent which could destroy civilization and do great harm to the environment, a large consignment of elements from space. Such deliveries are not as uncommon as was previously thought, particularly during the past twelve thousand years. Much evidence suggests that humanity witnessed, and was affected by, the break-up of a very large comet over this time period.