Final answer:
Modern humans spread out of Africa beginning around 100,000 years ago, reaching Europe, Asia, and Australia by approximately 40,000 years ago and the Americas around 16,000 to 13,000 years ago.
Step-by-step explanation:
Modern humans (Homo sapiens) originated in Africa about 200,000 to 300,000 years ago. The first significant wave of migration out of Africa occurred around 100,000 years ago. These early humans expanded throughout Africa, and by 40,000 years ago, they had spread to Asia, Europe, and Australia. The Americas were settled later, with human presence there dating from around 16,000 to 13,000 years ago, following migrations over the Bering Land Bridge during the last ice age. This migration pattern was influenced by the need to follow game, search for new food sources, and changing climate conditions, including glaciations. During this colossal global dispersal, early humans also encountered and interbred with Neanderthals, which was an important event in human migration and evolution. It is believed that all human species except Homo sapiens disappeared between 40,000 and 15,000 years ago, an event that can be largely explained by the 'out of Africa' model, which suggests that modern humans replaced other hominid species. Nevertheless, evidence shows that early humans managed to adapt to a multitude of environments and accomplished transcontinental and transoceanic voyages well before the emergence of agriculture or the development of what we typically consider 'civilization'.