In ancinet Jewish literature such as Wisdom of Solomon, Talmud, and
rabbinic writings, except the Bible, there is the idea of preexistence
of
human souls. Some ancient Jews believed that life begin at the moment
when a preexistent soul enters the sperm which is sown in the womb of
a woman or into the growing fetus, that is "ensoulment". But their
vies are variegated. Some believe that the ensoulment happens at the
moment of impregnation, while other assign it to differnt moments,
e.g., at fortieth or eightieth day of conception, or even later. Some
say the soul enters the fetus when it came out from mother's womb. I
like to know where did each of these different views come from. It
seems these ideas came from Greek
philosophers or medical doctors. But can we identify the exact sources
or origins, i.e., who and who said this and that, tracing each view
with precise documentation rather than in vague and general statement?

I would just like to point out that the idea of preexistence isn't
completely absent from the Bible.  In the book of Jeremiah, Jeremiah
is told that God knew him before he was formed in the womb, and there
are also passages in Job and Ecclesiastes that faintly suggest some
sort of preexistence.  It's an interesting question that was asked
here; I'll be curious to see what some researcher comes up with.

The Greeks got many of their ideas from Egypt, and in fact Herodotus
wrote "the Egyptians were the first to assert the immortality of the
soul, and that it passes on the death of the body into another animal;
and that when it has gone the round of all forms of life on land, in
water, and in air, then it once more enters a human body born for it;
and this cycle of the soul takes place in three thousand years".

Certainly, the Egyptians believed that the ba and ka left the physical
body after death, so it is possible they also defined a specific
moment when the ba and ka entered the body.  However, I have no proof
of this.

If you extend your enquiries to the transmigration of souls, you will
need to look at Hindu ideas on this question as well.

I think this could be a huge area of research.

Some arugue that the idea of preexistence of souls should be
differentiated from the idea of God's "foreknowledge" of future human
beings. In the latter case, the soul of a person was not preexistent
but only his or her "name" existed in God's mind. Besides, we also
neeed to consider the nature of the biblical authors' language. Is it
merely a poetic expression or integral belief of the authors? The
question is: Could these biblical authors know the idea of
preexistence, which is different from the idea of transmigration of
souls entertained by Egyptians, Pythagoras, and Hindus? Where did the
biblical authors learn the idea of souls' preexistence? The authors of
Job and Eccllesiastes may have been exposed to foreign influences. But
what exactly were theses influences? The rabbis afterward believed
that when God created the world he also created all souls and stored
them in a storehouse. When the time is full for a person to become
incarnate, he commands that soul to enter into a sperm and causes the
sperm to be sown in a woman's womb (cf. Midrash Tanhuma Pekude 3).
This idea could be very late, perhaps after 200 C.E. I like to find
out the origin of this idea. I wonder perhaps Helllenistic medical
thoughts played a role here. However, I am not familar with this
field. Aristotle seems to think that the embryo inherits vegetable and
animal souls from the (male) parent throuhg his sperm, while the
rational soul is ensouled from outside at a later stage of fetal
development. But I am not sure about this.