It was a harsh forbidding world that these humans set out to populate. The Earth was locked in the grip of a hostile climatic event called the "ICE AGE". Most of North America and almost all of Europe was covered in uninhabitable glaciers. The land that was ice-free was cold and barren tundra or rolling plains and steppes inhabited by large wholly herds of creatures that were very hard to hunt.
And yet our ancestors somehow managed to adapt to this land. each clan, in isolation, managed to hold on to the spark of the Divine Covenant between humans and the Great Spirit. They approached the challenge of survival with humility and with a spiritual resolution that guided them through the toughest of trials. And they prospered, and they thrived. The story of their survival was a story of cycles, from a cycle of one united community to a cycle of many isolated communities, and then on to a new cycle.
The ancestral humans were so uniformly successful that the population of each isolated group grew. As each community grew the posibility of two of these isolated groups finally bumping into each other grew also.
Inevitably, it finally happened. Somewhere on this planet, It may have been North America, or maybe Africa, or it may have happened in Asia...It does not matter where, what matters it that it finally happened. Two populations finally ran into each other. Each one discovered that they were not the only humans living on the Earth.
It may have happened on a hunting expedition. Perhaps a small group of scouts or trakkers walked up to the top of an infamiliar ridge and as they surveyed the prairie beneath them they spotted a small band of humans in the distance silhuetted against the setting sun. Of course, at first they thought it was members of their own community. It must be that pesky rival family that had been trying to wrest the leadership of the clan from the ruling family for years. Maybe they were making their bid for power somehow...but...how in the world did they manage to outflank them and get to this new and formerly unknown hunting ground ahead of themselves? Annoyance would turn to shock as they neared the other group to chastize them for challenging their authority and then gradually realized that these were not members of their community.
Then the utter trauma of the epochal event took hold as the members of each group gazed in amazement at the bizarre clothes of the other, their outlandish mannerisms, the color of their skin, the shape of their eyes. And if that was not enough, the final insult to their senses came when members of the other group opened their mouths and began making wierd unintelligeble chattering noises which they seemed to use to communicate! Nothing we can imagine today can possibly compare to that shocking moment exept perhaps the unexpected meeting with UFO aliens. Even that is a poor comparison because we nowadays expect such a meeting, some modern humans can't wait for it to happen. Others believe it already has. Those ancient ancestors had no clue, no preparation, no hint that this moment was going to come!