Where is the evidence? How do you know that they weren't simply humans?
From talk origins:
"Archaic forms of Homo sapiens first appear about 500,000 years ago. The term covers a diverse group of skulls which have features of both Homo erectus and modern humans. The brain size is larger than erectus and smaller than most modern humans, averaging about 1200 cc, and the skull is more rounded than in erectus. The skeleton and teeth are usually less robust than erectus, but more robust than modern humans. Many still have large brow ridges and receding foreheads and chins. There is no clear dividing line between late erectus and archaic sapiens, and many fossils between 500,000 and 200,000 years ago are difficult to classify as one or the other."
The article has a link to pictures of archaic homo sapiens fossils.
How do you know that they weren't simply humans?
Well, the line between human and subhuman was blurry in those early days, so it's hard to say. Impossible with any degree of certainty. Nevertheless, as you can see from the article, the "archaic" homo sapiens lacked a lot of important features of modern humans, but at the same time had lots of features we normally associate with apes. They had smaller brains, brawny, robust skeletons, large brow ridges, etc. There is also some evidence that they did not possess the full capcity for language that we moderns do. All of this would seem, IMHO, to make them subhuman.
On the other hand, they had a lot of physical similarities with us that would make interbreeding highly likely. And, of course, it is certain that they overlapped with modern humans before going extinct.
If they were not fully huamn, then they were not descendents of Adam and Eve. On the other hand, I see no theological reason to rule out the possibility that the children of the first couple interbread with them. Do you?