The Birthplace of Mankind

We seem to forget the chronology of life on this planet. First human beings were of dark skin, found in what is now known as Africa and built the first civilization. So if all human beings are descendent from that first of mankind and there is proof the the population of the other so call continents migrated from Africa, then we are all one people---Black regardless of skin color and language. Some of you will take me back to the Bible. Well, what happened to those people who multiplied before so called Adam and Eve? And, Where did Cane get a ife? Is it possible that Adam and Eve were not the first people but the first in the Garden?