As summarized by Chanie Koplowitz Stein.
The womb is a finite universe in which in nine months' time worlds are formed to break out and emerge as individual human beings. Within this environment inside our matriarch Rivka, two worlds were being formed simultaneously, twins who would be named Esau and Yaakov. Would these worlds live in peace and harmony, or 
Esau, at least in the symbolic sense, is no longer the firstborn.
would they collide? When were their trajectories decided, how would they develop, and what would the final outcome be?
The Torah tells us that the children agitated within Rivka. Our sages explain that, already then, in embryonic form, the struggle between the forces that would come to symbolize the essence of Yaakov and Esau were in conflict; and when they emerged from the womb, that interaction was evident as Yaakov, from within the womb, grasped the heel of his already emerging brother. The names the twins are then given add yet a further dimension to the essence of each. The first to be born was Esau, so hairy that he appeared to be more than a newborn, fully formed and complete. His name, Esau, means "done", complete. His brother, Yaakov, was also named for the physical characteristic he displayed, holding on to the heel of his brother, ekev, the "heel".
The overriding question remains: Why was it necessary to have these two worlds begin their existence as twins? What is the import and the message implied therein? And why, if Esau is the totally physical twin and Yaakov the spiritual twin, did Esau emerge first as the bechor, the firstborn?
In fact, that was the point of the entire situation. Yaakov and Esau were meant to create a partnership similar to the later partnership of the tribes of Issachar and Zevulun, where Issachar would be the scholar and Zevulun would support him by going out into the world, across the seas, as a merchant. Although Yaakov was completely spiritual by nature, he was nevertheless a human being. He would require food, shelter, clothing and whatever else a person needs while he sits in the yeshiva, learns and continues to build up his spiritual essence. Esau was supposed to be the individual to provide that support for Yaakov.
Esau was supposed to be that man of the world, knowledgeable and complete, as he was at birth, understanding the mission of Yaakov and providing the sustenance Yaakov would need to complete this task. This support was to be Esau's mission, and by doing so he would be a partner in creating the spirituality of HaShem's presence on Earth. It is for this reason that he was meant to be the bechor, the firstborn, whose responsibility it is to see that the rest of the family has the wherewithal to accomplish their mission, for without physical sustenance a person cannot focus on learning. In fact, for this reason Zevulun, the merchant, gets his blessing before Issachar from both Yaakov and Moshe before their deaths.
But the conflict already began in the womb. Yaakov was content to sit in the tent of Torah and share that merit with his brother. Esau, however, was not interested in spiritual merit. His portion was the physical world and he was not willing to share it. If he went out into the world, caught the prey for food, or did business, or even stole, he wanted to retain all the profits for himself. His focus was completely on the here and now, never on the spiritual essence of the World-to-Come. Even if he did a mitzvah, like honoring his father, the purpose was not to build his spiritual world, but rather to gain some benefit in this world, such as receiving blessings from his father.
If this partnership was not going to work, then Esau's role as the firstborn is contraindicated. Yaakov then needed to take on the role of provider, as well as that of spiritual leader. He grabs onto the heel of Esau, taking on Esau's persona as the provider of physical necessities. If Esau will not fulfill his mission and Yaakov must do so, then Esau, at least in the symbolic sense, is no longer the firstborn.
This understanding manifests itself more completely in the incident with the red stew. That Yaakov is doing the cooking already proves that Esau was not providing for the physical needs of the family. So when Esau comes in and asks Yaakov to pour some of that stew down his throat, he has already relinquished his responsibility as the firstborn. The deal he now makes with his brother merely reinforces his preferences - 'I am only interested in the pleasures of this world; give me food; what do I need the birthright and all its responsibilities for?' Yaakov asked for that deal to emphasize that their symbiotic relationship needed to be severed and henceforth they would need to be separated, just as day and night were originally intermingled and HaShem separated day from night.
That being the case, when Yitzchak later wants to bless Esau, and Yaakov supposedly usurps the blessing, Yaakov is not really being deceitful. He has already accepted the responsibility of Esau's role . Now he symbolically dons the hairy outer layer that makes him completely "done", and he enters his father's chamber. When he answers Yitzchak's question as to his identity, he can truly answer, 'It is I, the true essence of Esau your firstborn.'
Obviously, this reasoning would not sit well with Esau, and Yaakov flees to Lavan. There, he marries both Rachel and Leah, Rachel who was his soul mate and Leah who was supposedly destined to marry Esau. Now, since Yaakov has integrated within himself the quality and mission of Esau, Leah could become the wife of Yaakov, especially as the one more in tune with practical matters.
Let us, however, get back to the actual blessing Yaakov receives. "And may God give you the dew..." Yitzchak began the blessing with "and". That's strange. "And" connects one thought to another. What was this blessing connected to? It appears that Yitzchak was saying that the blessings should continue by stopping and beginning constantly. Yet, the essence of blessings is that they are permanent immediately.
Yitzchak began the blessing with "and". That's strange.
Herein lies the continued partnership of Yaakov and Esau. The blessing Esau eventually received from his father was a completely physical blessing, the fertile Italian peninsula and the ability to be a mighty warrior. But he can also become his brother's master if Yaakov fails to live up to his mission. In other words, there was still a symbiotic relationship between Yaakov and Esau, but now it was turned upside down. No longer would Esau provide for Yaakov, but he would be the stick to make Yaakov lift up his heels and keep on his toes, and continue striving for higher spiritual levels.
Yaakov and Esau may be walking the same path in this world. There are all kinds of objects and situations along the road. Esau is content to see all this as just more details of a physical, horizontal journey. Yaakov, on the other hand, sees each object in his path as a message from HaShem, either as an obstacle to overcome or as a tool to use in reaching greater spirituality. He sees himself as the heel, humble and striving upward, while Esau sees himself as always complete, never needing improvement. Nothing ever changes for him. But Esau is there, ready to pounce, and HaShem is always keeping His watchful eye on Yaakov and his descendants.
Let us hope that we will always act as a proper vessel to continue receiving His blessing until the end of days, when the partnership between Yaakov and Esau will again be the positive relationship it was meant to be.