A number of theories exist for our earth-plane biological origin. Some suggest that our ancestry dates back to the Atlantean era, where races were formed from a number of warring planets in other solar systems. However, origin itself may have little significance when compared to the choices we can personally make that affect our soul growth.
The limited understanding of our higher conscious is connected to reincarnation cycles, evolution, physical environment, conditioning patterns, and the history connected to why we are here at all. When man initially embarked on an Earthly sojourn, eager souls, collectively inspired by their own light of the Collective Spirit, deemed that the chance for survival in this dimension and the new world, would be at the price of the memory of self (until spirit was found). All of this occurring millions of years ago in earth terms.
If all humans remembered their past lives, there would be chaos, because the physical laws here denote certain forms of separateness and through evolution. Part of our physical survival is connected to forming family or group patterns that involve learning and teaching with others.
The existence of many races and tribes, each with differing experience and focus, created different cultures with unique languages. As we have seen throughout the history of man, separateness and [cultural] selfishness can generate violent behavior at times. This occurs not only as we distance ourselves apart from one another, but further from the source.
(See also Adam and Eve)