How did geographic isolation and cultural diffusion shape society in ancient Egypt?

Geographically, ancient Egypt was an isolated region. There was a big desert to its west, what is now called the Libyan Desert. Its north was surrounded by the Mediterranean Sea and its east by the Red Sea. The Kush Kingdom covered Egypt’s southern border. As such, there were only two points of entry by land into Egypt: the south or the northeast. Most of Egypt’s enemies entered it through the northeastern route via Palestine and across the Sinai Peninsula. To protect itself against these invaders, Egypt built fortresses along the Sinai Peninsula. The surrounding deserts and oceans also acted as natural borders that kept out intruders.
The Egyptians and their southern neighbors from the Kingdom of Kush interacted a lot. In fact, they even ruled each other at certain points in history. They were also great trading partners. Evidence of the cultural diffusion between these two kingdoms exists in similarities in religion and burial rites. The Kushites buried their dead in pyramids that resembled the Egyptian pyramids. Both cultures worshiped the gods Osiris, Thoth, and Isis.
http://www.angelfire.com/nt/theology/06egypt.html