I contend that a better example of a short species evolution is the Democrat of 1942 and the Democrat of 2006.
Their brains and spines have shrunk perceptibly. We soon believe they will stop breeding altogether
They are much more clever than that, the ones that do breed will have abortions, and ones who might breed will join in civil unions, and the ones that avoid civil unions will think that they are homosexual and the ones that....
Well, being anti life does come at a price.
I believe what you are describing is the first time an entire species running off the proverbial cliff at the same time.