Was it the impact of an enormous asteroid, or did nest-marauding mammals end the dinosaurs' reign?

Either phenomenon may have put the nails in the dinosaurs' collective coffin, says Frank Paladino, chairman of the biology department at Purdue University's Fort Wayne, Indiana, campus. But he says there may have been a third potential culprit--temperature-dependent sex determination, or TSD--that ultimately caused the demise of these giant reptiles.

"We believe that dinosaurs were probably much like their modern counterparts: alligators, crocodiles, and sea turtles," Paladino told me. "All of these animals today exhibit some form of TSD."

So how does TSD work? For many reptiles, the incubation temperature of eggs often determines the sex of the hatchlings. A shift of a few degrees is all it takes for the eggs to yield all-female or all-male offspring.

Take alligator eggs, says Paladino. If these leathery-shelled ova are incubated at 86ºF during the middle stages of development, only females will hatch. If the same eggs are incubated at 93ºF, only males will emerge. At temperatures between these extremes, a mixed litter of males and females will be born.

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Makes sense. Consider, when that meteor hit the planet, it was said to have plunged the earth into an ice age. Granted, the temperature was probably gradual at first, but how many seasons would it take to totally irradicate a species that was so thermal dependant?

The idea is sound with current theories and could possibly be yet another of the underlying elements which destroyed them.