Dear Jou,
I found some more suttas in the samyutta nikaya about samsara.
http://www.accesstoinsight.org/canon/sutta/samyutta/sn15-014.html
At Savatthi. There the Blessed One said: "From an inconstruable
beginning comes transmigration. A beginning point is not evident,
though beings hindered by ignorance and fettered by craving are
transmigrating & wandering on. A being who has not been your mother
at one time in the past is not easy to find... A being who has not
been your father... your brother... your sister... your son... your
daughter at one time in the past is not easy to find.

http://www.accesstoinsight.org/canon/sutta/samyutta/sn15-009.html
Why is that? From an inconstruable beginning comes transmigration. A
beginning point is not evident, though beings hindered by ignorance
and fettered by craving are transmigrating & wandering on. Long have
you thus experienced stress, experienced pain, experienced loss,
swelling the cemeteries -- enough to become disenchanted with all
fabricated things, enough to become dispassionate, enough to be
released."
Robertk