Congress codified the disparate impact theory for Title VII when it amended that law in 1991.
"I think this evidence bodes well for the impact theory," Dr. Becker said.
When people began to believe the impact theory, they started looking for other Cretaceous-end anomalies.
The giant impact theory provides a satisfying explanation for the orbit, size and basic physical characteristics of the Moon.
Those sniping at it are not at least not yet—arguing that the impact theory is completely wrong.
The seminal text, which was reissued in 2001, examines the mathematics of impact theory and shows how different materials, like cars in crashes, react to rapidly applied stress.
But whether this "disparate impact" theory can be used for another important category of job discrimination, discrimination based on age, is an open question.
Gerta Keller, a paleontologist and professor of geosciences at Princeton University, said the research by Dr. Landman's group "shows the complexity of this extinction event and the difficulty explaining it by the currently popular impact theory".
Sure enough, different parts of the present moon's crust, recovered by various missions to the lunar surface, differ in age by up to 200m years, a fact that has long puzzled selenologists but which the impact theory neatly explains.
Employer groups and conservative legal organizations have recently taken aim at the disparate impact theory across a variety of civil rights statutes, where the theory was not explicitly provided by Congress but rather inferred by the Supreme Court in an earlier, more liberal day.
Reductions in force that fall more heavily on older workers but that could not be challenged under the disparate impact theory would, Mr. Crabtree said, "allow employers to get rid of older workers where there is a corporate culture pervaded by ageism".
