(It may be asked that if this date is indeed when Adam and Eve were created, then how come the lifespans of Adam and his descendants--up to Noah--(and taking into consideration the overlapping of generations) simply do not add up to such a lengthy period of time? Well it may be that we have more than ten generations from Adam to Noah, and that we were given ten antediluvian individuals in the biblical record because the number "10" represents the ideal--such as in the Ten Commandments, which we humans could never attain to.)
Yes Adam and Eve sinned, but their appearance in the Middle East was nonetheless a good thing for mankind. After untold centuries of human history, God would (for the final time) directly create a man--and a woman to be his helpmate. That's why this couple were created just as the wave was moving upward. It would be from the Adamic line--by way of Seth of course--that Jesus Christ would be born. And the reason we had two more downward movements of the wave is because the serpent fathered his own line by having sex with Eve--from which union came Cain. Obviously, we had two more dips since the time of the Garden is because it is--after all--a sine wave.
The Great Pyramid of Giza was built around 12,000 BC just as the wave was moving downward (an overall decline on the earth). Atlantis had grown corrupt (again). It's theorized that Christ had appeared on the earth at that time. He was killed and buried in the King's Chamber in the Great Pyramid, but this tomb is empty: he was resurrected.
Atlantis grew steadily worse in its corruption, so that God hit it with tidal waves and it sunk beneath the waves around 9,600 BC (just below the timeline, as the world was once more engulfed in night).
If it is true that the Son of man incarnated on the earth at that time, then the legend of Toth may be how that story has come down to us. From what I gather, Toth came to Egypt from an Atlantis engaged in wickedness. Once in this land--that would one day become known as "Egypt"--he set about to build the Great Pyramid. And it may be that he was slain before he could put the capstone on it (being the top corner). Jesus says in Luke 20:17: "What is this then that is written, The stone which the builders rejected, the same is become the head of the corner?"