Kendall,
I just saw a History Channel program on the Library at Alexandria. Some scientist claimed that it set back mankind's development by hundreds of years. Imagine: the Civil War could have been atomic. Or maybe, a slower moving society might have been able able to use the power more efficiently/productively.

But if we are being philosophical, my vote would go to the loss of knowledge of our earliest ancestors. If we could each trace our roots back to a single pair of great-great-ever so great grandparents, maybe we could all live as one big happy family. Maybe Jon's Garden of Eden gets my vote after all.