The concept of human-like creatures before the first human beings is well known. There were actually 974 generations of human-like creatures before Adam and Eve. All the findings of Paleontologists of human like creatures (Neanderthal, homo-erectus, homo-sapiens, Cro-Magnon, etc) is a very incomplete list since we know that it totals 974 different species. Why Hashem created all these prehistoric species before the first humans is a very complicated topic. But, since Adam to Moshe Rabbeinu is 26 generations, we see that the mention in Tenach about the Israelites being the thousandth generation, now becomes clear (Exodus 20:6 and Deuteronomy 7:9).
One additional clarification is the age of the universe. For more details, go to my post of 3 Apr 2012 entitled:
The Age of the Universe