Final answer:
All fossils from the human lineage for the first several million years are found in Africa. The "Out of Africa" model, supported by genetic data, posits that Homo sapiens emerged first in Africa and then spread across the globe. Alternative theories like the "multiregional evolution model" have lost ground in the face of recent evidence.
Step-by-step explanation:
For the first several million years of human evolution, all the fossils from the human lineage are found in Africa. Research has shown that all human genomes tested outside of Africa have close ties to the genomes of people in Africa, indicating a common descent. Moreover, genetic variance observed in Africa is greater than that found in the rest of the world, supporting the idea that humans most likely descended from this continent.
The "Out of Africa" model is the most commonly accepted theory for human evolution, suggesting that modern humans (Homo sapiens) emerged first in Africa approximately 200,000 years ago. Eventually, they spread out to populate different parts of the globe, including interbreeding with Neanderthals. Fossil remains found in Europe and Africa, dated between 300,000 to 800,000 years ago, appear to be intermediate between Homo erectus and modern humans, providing further evidence for this theory.
However, some have proposed a "multiregional evolution model" where Homo sapiens may have evolved from Homo erectus in several places simultaneously. This concept has faced challenges, especially in light of recent genetic data that tend to support the "Out of Africa" theory. As new archaeological and genetic evidence is gathered, our understanding of human evolution continues to evolve, revealing the intricate history of how Homo sapiens came to be the sole surviving human species.