"Scientists in the working group say the evidence for such impacts during the past 10,000 years, known as the Holocene epoch, is strong enough to overturn current estimates of how often the Earth suffers a violent impact on the order of a 10-megaton explosion. Instead of once in 500,000 to 1 million years, as astronomers now calculate, catastrophic impacts could happen every few thousand years."

http://www.iht.com/articles/2006/11/14/news/meteor.php

Here’s a more detailed study of suspected paleo-tsunamis from Australia. Runups in excess of 20 miles from shore.

http://library.lanl.gov/tsunami/213/scheff.pdf

Here's information on confirmed land impacts, somewhat dated. No obvious smoking guns here, although there is an impact in S Africa (Tswaing)around 220K years ago. Tha database can be sorted by name, age, and diameter. Photos also available.

http://www.unb.ca/passc/ImpactDatabase/

“A newly presented mathematical argument suggests that the birth of Homo sapiens was guided by catastrophic asteroid or comet impacts, which created climate conditions that competing species, frankly, couldn't handle.
…
Basic numbers questioned
Of course to affect human evolution in any fashion, a space rock first has to hit Earth. But "no one knows how many impacts took place, or when, or with what severity, over the past 5 million years," said David Morrison, an asteroid expert at NASA's Ames Research Center in California.
Morrison told SPACE.com that instead of the 20 potentially devastating impacts assumed by the study, he expects there were probably only five or 10 with enough energy to create global environmental effects.
"But we know very little about specific impacts in this time frame, and virtually nothing at all about their actual environmental effects," Morrison said, adding that there is "no evidence of an impact associated with a hominid extinction."
Morrison did not discount the whole idea, however.
"I would be surprised if impacts had not had some influence on early hominid populations and perhaps evolution," he said. "On the other hand, I am not convinced that impacts led to numerous extinctions in the past 5 million years. This is all interesting speculation, but specific data are lacking on either impacts or extinction events and there is no known correlation between the two."
Peiser counters that the estimates used in the study are "very conservative." He acknowledges that shortcomings in the human fossil record (fossils on land erode more easily than those in the oceans) "are far too big to allow any direct correlation between impact catastrophes and hominid extinction." But he said that the study shows that "impact catastrophes that occurred during the crucial period of human evolution should no longer be ignored."
Still, it is clear that more research will be needed before any consensus emerges.
"What [Peiser and Paine] may have added," said Balding, the statistics professor, "is some quantitative simulations to make more precise some well established speculations."

http://www.space.com/searchforlife/h..._010424-1.html

And oh, by the way, meteor impacts are also responsible for the evolution of sex …

http://www.space.com/scienceastronom...ex_010710.html

Feh, as someone who works on mass extinctions, I can tell you that people are quick to blame impact for *every* event. Where's the evidence?

__________________
Do not taunt Happy Fun Ball.

Mass extinction would be an extreme case. I think what the articles suggest is that meteor impacts may be more frequent than we previously thought. These impacts could affect prehistoric human populations through their effect on climate and Tsunamis. Yes, evidence is scarce, but that doesn't mean that we should close our minds to the possibility.