I really have to say: TopHat and dido have shown themselves to be the best female clowns I've ever seen on this board. They're about the equivalents of our old friend scholar pretendus.
Greendawn, Neanderthals seem to have died out around 25,000 years ago, having been replaced for as yet unknown reasons by modern humans. Neanderthals, according to the best DNA evidence available, are not the same species as modern humans. How can that be explained in creationist terms?
As for the long held view that Neanderthals were stupid brutes, that's unfortunate, but that's the way science works -- it's self-correcting over the long haul. On the other hand, science has contributed greatly to correcting wrong views held by Christians for centuries, such as the notion that the earth is the center of the universe. I have no doubt that, in the long run, whatever Christianity is in a few hundred years, it will largely accept evolution just as surely as most Christians today accept that the earth goes round the sun.
As for why civilization took so long to develop, no one can say with certainty. However, nature has delivered some severe blows to life with unfortunate regularity, and I suspect that that's one of the main reasons for the delay.
For example, huge volcanic regions like Yellowstone, Long Valley and Toba have erupted from time to time, causing massive climate disruptions. The Toba eruption in Indonesia some 74,000 years ago was the biggest that geologists have been able to find in the last few million years. It apparently caused about six years of extreme cold, even in the tropics, which in turn caused much plant life to die or not to produce the normal amount of vegetation to feed humans and animals. Genetic evidence indicates that most modern humans died out at that time, since there is a "genetic bottleneck" evident in our genes, which indicates that only a small population in Africa survived the extreme cold. That such disruptions can occur is shown by the climate disruptions caused by modern volcanic eruptions such Pinatubo and Krakatoa. The most severe modern disruption occurred in 1815-1816, when the eruption of Mount Tambora in Indonesia killed close to 100,000 people outright, and led to "the year without a summer", during which thousands of Europeans starved because summer crops failed. There was snow all summer in New England and much of Europe. The Toba eruption was about 100 times greater.
Yellowstone erupted about 600,000 years ago, certainly leading to similar climate disruptions. What effect that had on human populations is unknown, but probably severe, judging by what is known today. The recurring ice ages also cause a great deal of disruption, where roughly every 100,000 years the pattern of long, slow decline to the severest of cold conditions followed by 10-20 thousand years of relatively warm weather recurs. During these cycles, climate can shift radically. Ice cores from Greenland and Antarctica show that, about 10,000 years ago, climate entered another warm period, which is, for unknown reasons, the stablest in terms of climate seen in the entire record of ice cores. Such stability, unknown until then, likely provided the conditions that allowed humans to form stable farming societies for the first time.
So the fact that civilization took a long time to develop is not nearly as mysterious as you want to believe. But the sciences that look back to these times are still in their infancy, and of course there are still many unanswered questions. These cannot be answered very well by creationists, either, so creationism in any form is of no help in giving real answers. Young-earth creationists reject almost all of modern science. Old-earth creationists simply have to throw up their hands and say, "God did it", until science comes up with something they can sink their teeth into.
AlanF