The difficulty here is that the date of Adam can be calculated from genealogical information in the Bible to be approximately 6000 years ago, or possibly a little longer. So human remains that are much older than that cannot have been descendants of Adam.
There are three major views that attempt to account for this discrepancy.
One view is that there were other people on earth in addition to Adam’s descendants, and the very old human remains are from the same line as these other people. Those who follow this view often point out the “other” people hinted at in Genesis 4. (The hints are: who was Cain afraid of? who did Cain and his siblings marry? and which people began to worship the Lord?) Under this interpretation, it must be explained how Adam can be said to be “the first” man, but that is a different subject.
Another view is that such human remains arise from an “earlier creation” about which we know very little. There are many possible ways to formulate such a view, but a key element is usually that any earlier humans were not ancestors of Adam or any currently living people. In this view, Adam is the first of “currently living people”. Perhaps there was some time period between when the earlier humans and Adam lived.
A third view is that there are no human remains so old, and scientists are simply mistaken in their dating.