Before I begin . . . it is important to recognice that the Bible does
allow a lot of room for guessing . . . we are not told everything . . .
we MUST be careful as to what we say is fact and what is just an idea.
The Pharasees did not recognize who Christ was becasue they "KNEW" that
the Messiah would be a political leader. Let us not fall into the same
trap.

That said . . . it is likely that were was a layer of water above the
earth, or maybe even more likely . . . ice. Such a layer would prevent
UV rays, reduce sun damage and extend life spans. That layer of
ice/water is the best translation we can come up with for teh idea of
"firmament" as mentioned in Genesis.
If you read through Genesis and add up the ages . . . taking into
account when each was born you will find that the time from the creation
of man to the flood was about 2000 years. [At age 150 Adam had Seth
(btw it here states that Adam and Eve had MORE childres) at age 105 Seth
had Enosh, at age 90 Seth had Kenan, at age 70 Enosh had Mahalalel, at
age 65 Mahalalel had Jared, at age 162 Jared had Enoch, at age 65 Enoch
had Methuselah, at 187 Methuselah had Lamach, and Lamach at age 182 had
Noah. At age 500 Noah had 3 sons, Shem, Ham, and Japheth] During that
time you had people with life spans approaching 1000 years. That makes
for a lot of people. How old were Cain and Abel when their exchage
happened. It is possible that both were a couple hundred years old when
Abel was killed.
Genetisists have agreed that even by the time of Noah the gene pool
would be very large. What that means is that between Noah and his wife
it is very likely that they had the genetic material for every race we
see today. Cain and his family were not alive after the flood, the
Bible clearly states that all mankind was destroyed.

For those whole like numbers we have 23 pair of chromosomes . . .
between a mother and father there are 4 different possiblities for the
pairing of each chromosome (2 from dad, 2 from mom, 2x2=4) take 4 to
the 23rd power(the number of chromosomes we have) that is
4x4x4x4x4x4x4x4x4x4x4x4x4x4x4x4x4x4x4x4x4x4x4 or 70,368,744,177,664 and
you will have the number of possible offspring. I believe that 70
trillion possibilites could more than account for races and diversity
among humans.

Now this is completely void of of teh number or genetic mutations.
These mutations can happen just from two strands of DNA crossing over
and switching "legs". Take that into account and the number of
possibilities is all but limitless. If you would truely like to
understand how many posibilities there are, take a class in genetics.
Add all the different kinds of mutations to this equasion and it is
positively mind blowing.

As I said before . . . don't put faith in what the Bible doesn't say . .
. and if it doesn't talk about it, it doesn't mean it didn't happen. We
must take all of scripture into account when contemlplating such large
ideas. We are only setting ourselves up for failure if we do otherwise.

I'm not sure how far back the tradition was used before Christianity .
. . but I do know it was used especially during the time of Nero to
secretly meet and identify other Christians. It was used to designate
meeting places or in conversation one person would casually draw an arc
in the sand with their foot. The other would complete the fish and
quick erase it.

for those who say Satan does not exist or is already defeated . . .

first I encourage you to get out of the country . . . Satan has enough
of a hold on us in the states that he doen't need to use tactics he once
used. Travel to places in Africa and South America . . . I have seen
people possesed and spirits cast out . . . I have witnessed outright
demonic war and oppression . . . it exists and cannot be denied. In the
states we fill our lives with busyness and worries, we have no time to
truely serve God, so Satan has very little work to do here.

second . . . when Christ died he died that we might live . . . I suggest
you read your Bible again. Why would satan be called "the Prince of
Darkness" in the New Testament if he is alrady defeated?? Why would
paul warn us against him?? Read the book of Revelation and Daniel again
. . . I won't argue any order to events . . . but it seems very clear
that in the end times the devil is alive and at work.