Final answer:
The 'Out of Africa' hypothesis posits that modern humans originated in Africa then migrated worldwide, supported by genetic evidence and environmental factors like climate change.
Step-by-step explanation:
The "Out of Africa" hypothesis suggests that early humans emerged from one location somewhere in Africa and then spread out to populate different parts of the globe. This theory is supported by genetic research; most human genomes tested outside of Africa show close ties to those of people in Africa, along with the fact that there is a genetic variance in Africa not found elsewhere in the world. Climate changes, such as increasing aridity, likely spurred Homo sapiens to begin their migrations out of Africa approximately 200,000 years ago, with further expansions around 100,000 years ago.