This week's Parsha contains a parallel which connects the beginning of mankind to a much later generation...
In this week's parsha the first man was created. From him came woman. From them came the rest of mankind.
Hashem first creates man and rests him in Gan Eden where he is to "watch and "guard" the Garden. He was told not to eat from the Tree of knowledge - but he does. He is then punished. He would be exiled from Gan Eden and would have to work hard to achieve what would formerly have been a relatively easy task.
Adam and Eve have two children and eventually each one brings a Korban to Hashem. Only one of the Korbanot were accepted. This caused Cain to become angry and kill Abel. At this time, the land was still cursed because of his father but he was able to avoid this curse somewhat by becoming a shepherd while his brother continued to work the land. He only depended on the land for food for his animals. Now as a punishment he would be forced to wander the land afraid of being killed by anyone who would find him. Hashem, though, gives Cain a "sign" that would protect him and a decree which would lighten the punishment.
Many generations later Hashem "creates" a nation and then places them in a land where he is to "watch" and "guard" the land and live in the land by "watching" and "guarding" the Mitsvot. The nation was told not to do certain things such as following other gods - but they did. They are then punished for their misdeeds. They would be exiled from their land to a foreign land in which they would have to work hard to achieve what would formerly have been an easy task.
A generation passes and the "Beit Hamikdash" was allowed to be rebuilt but not everyone returns and even those who did return cried over the beauty that was lost by the first "Beit Hamikdash" which was destroyed during the first exile. The Korbanot resume but eventually Hatred between brother and brother results in both civil war as well as exile in which the nation would be forced to wander other lands afraid of being killed by anyone who would find them. Their only relief from this persecution would be that Hashem had told them that he would protect them and return them eventually.
As we, the descendants of Avraham who was the descendant of Shet the son of Adam, return to Israel - return to our "set" place, we have the possibility of returning to the Gan Eden like status. We have to be careful not to make the same mistake made by the generations before and regain what we lost. While Cain was told that he would be protected and then punished - Hashem told us that we would be protected and returned. Adam's eating from the tree of knowledge caused him to understand the difference between good and bad and now he would have to learn to control the two. We received the Torah in order to control the good and bad. Maybe when man learns to control the two by "watching" and "guarding" the Torah he can finally achieve his former status and the way to the Tree of Life will no longer be guarded so that man may eat from it and live forever as it says in Parshat Breishit - ואכל וחי לעלם - Va-achal, Vachai L-olam!