Final answer:
The African Replacement or "out of Africa" theory suggests that modern humans emerged in Africa around 200,000 years ago and replaced all other human species as they expanded globally 100,000 years ago, including Homo erectus and its variants such as the Neanderthals.
Step-by-step explanation:
Hypotheses of Human Evolution from H. erectus to H. sapiens
One prominent theory to explain the transition from Homo erectus to Homo sapiens is the African Replacement model, commonly referred to as the "out of Africa" theory. This model proposes that modern humans evolved in Africa approximately 200,000 years ago and began a second major migration wave out of Africa around 100,000 years ago. This resulted in modern humans spreading across the globe, replacing other hominin species, including H. erectus and its regional variants like the Neanderthals and Denisovans.
H. erectus had migrated out of Africa in a first major wave about 1.5 million years ago, settling in regions such as Eurasia. This species of human had enhanced capabilities like the use of fire and hunting. However, according to the African Replacement model, the emergence of anatomically modern humans in Africa led to these earlier forms of humans being replaced as H. sapiens expanded into their territories.
There is ongoing debate and research into this evolutionary transition, involving fossil finds and genetic analyses. The interaction between changing climates, migration patterns, and the evolution of human species, such as H. ergaster evolving into H. erectus, contributes to the complexity of human evolution narratives.