Exactly. There are some great theories out there by evolutionary biologists.

So the idea is that we adapted a long time into trees, then the trees receded, and we adapted to the ground.

Now that we had gripping hands, and feet that could walk us places, we started being able to shape our environment and our tools, which led to greater intelligence.

Combine all of that, leads to us spreading out. Humans that went borth to Europe adapted to the lack of sunlight evolved. The humans that went on to asia evolved differently, to their climate, and they were the ones that were the ones that kept migrating, until they got to the americas (land bridge from russia to alaska that was exposed when ocean water receded into the ice caps - ocean water evaporates, clouds flow over the continents, it snows/rains, that precipitation turns to ice and stays as ice, ie a glacier, thus leading to the exposed land bridge). There they kept migrating south. The evidence for this is found in similarities that asians and native americans share genetically.

TL;DR We evolved in trees, trees stopped growing where we were, we evolved for the ground, ground got dry, we evolved to travel. We traveled far while the oceans were low. Go humans!!