>raybin wrote-
>emailed Y Kleiman with this question and he said
>the Jewish calendar begins on the eighth day
>after creation, after the creation of Adam, so
>there may have been prehistoric humans whose DNA
>was continuous to Adam. I hope I quoted him
>correctly. I still don't get it. Does that mean
>that not all people are descendants of Adam,
>since there are a few clans that date back 10's
>of thousands of years?

gerald shroeder deals with this in
book- The Science of God
book- genesis and the big bang.
(not book - 'hidden face of God', - that is just about nature)

The book "the science of God" addresses your q very well in the early parts. The talmud mentions ppl before Adam that looked like man but were not considered man.

regarding the 5756 years, that is from Adam (so, from the point on the 6th day that Adam was born).

The first 3 days - sun wasn't as we know it, shining through the heavens. It was only like that on the 4th day. The light on the 1st day was a different light, not sunlight. So in the first 3 days, there was no daytime and nighttime.
We have a tradition that those days (all 7? or perhaps just 6?) contained eras.

Rabbi dovid gottlieb of ohr, in his audio tapes online explains that of any evidence of 'people' before 5756(assuming their dating is correct), there is no linguistic evidence. So, they may well be primitive creatures with some physically human features, but still, not considered man.

The tiny ppl hunting tiny elephants , a hell of a story. they were termed 'the hobbits' by the media.
There was a debate whether they had an illness that made them small. or whether they werwe a different species.
http://news.bbc.co.uk/2/hi/science/nature/3948165.stm
http://news.bbc.co.uk/1/hi/sci/tech/4331252.stm

they look more like little neanderthals from that pic second link.