...Bachya writes that the world is due to last for 49,000 years or seven sets of seven thousand years. Each set of 7000 years is made up off 6000 years of ‘normality’ and 1000 years of ‘Shabbos’. Year 50,000 is the jubilee year and everything sort of ends there. Bachya does not say much more than this. To me it seems clear that Bachaya understands that we are at present in cycle number one.
The Tiferes Yisroel uses this Bachya but adds more. Although he does not bring an actual source he says that books on Kabbalah state that we are at present well into cycle number four. (I.e. the world is 26765 years old). He then goes on to say how the recent (recent for his time) archaeological findings had proven that this was indeed the case. Archaeologists had found four distinct layers of strata – a stratum for each cycle. Each stratum had remains of different animals. The earlier the stratum the more crude the animal (dinosaurs); the later the stratum the more refined – the world gets better and better in each cycle. The previous cycle he claims had seen the first type of human (Neanderthal Man ?)– we are the second sort of human to walk the earth and better than the first as our minds are far more developed. At the end of each cycle a cataclysmic event takes place destroying all that has been before. We are reborn into each cycle which is the meaning of "Resurection of the Dead" and answers the initial question. The story of Genesis refers primarily to our cycle – number four. The first letter of the Torah is a beis and in the Torah scroll this beis has four vertical on its topmost tip. Beis equals two which represent the fact that we are the second sort of human, while the four lines infer that we are in cycle number four.
Good stuff, read the whole thing!