"Okay. On what basis do you make this hypothesis?"
Thank you. Now we are getting somewhere.
I base it on the molecular DNA evidence as presented in this thread...
http://www.freerepublic.com/forum/a3b47d7b94f92.htm ...and some more similar evidence that has come to light since then. THey did a study that sequenced a LOT more base pairs and STILL came up with a date for mankind's last comman male ancestor of < 50K years ago. Add to it the Vela Supernova may well have caused mutation rates in the past to be higher than now. This would mean that the actual dates are even less, since it is extrapolating based on todays rates.
Add to it the "Cultural Big Bang". Human culture, art, relgion, and the like, do not slowly evolve. They show up suddenly and fairly recently. On viewing some cave art that was among the oldest known, Van Gough emerged from the cave and exclaimed, "We have learned nothing!"
Add to it that a fossil "gap" appears on the near end of the scale. With DNA tests ruling out Neadertal man as an ancestor, and a preponderance of evidence that the other candidates went extinct about 100K ago, there was nothing around for modern man to evolve from.
VadeRetro and I have had good go rounds on this, with him trying to find good candidates for that 100K to 50K gap. He will find one, but then to his credit when more evidence comes forth that shakes the date he will fess up, while never letting go of the hypothesis he chooses to defend.