To escape famine and disease. And find saftey in more settled climate and environment.
In the book of Genesis from the Old testament in the Holy Bible it is stated that human beings were created in the image of God, First God created Adam, the first man and after God created Eve the first woman, using a rib from Adam as the source to create Eve.
Ancient Egypt, because it the unification by King Menes and the building of monumental pyramids and temples and last but not least the effective system of medicine.
Europeans were originally motivated to explore the seas to discover previously unknown lands, especially after the contact with America, where europeans found all kind of valuable goods. The portuguese were the first to pursue maritime exploration, soon to be followed by the spaniards.
