I think Kara just crashed and died on "Earth" the previous year, where everything else had been destroyed by the nuclear war 2,000 years before. Her body still had hair and there was visible dried blood on her dogtags. It was the other stuff that was all ancient. (Though really, after that much time there shouldn't have been even the exposed metal structures and fragments of bone from the former inhabitants that we saw laying around. The only non-fossil signs of human-esque habitation should have been stone structures in arid regions if I'm remembering correctly how fast weathering and oxidation occur...)