Here's a breakdown of the evidence:

* Fossil Evidence:

* The oldest known fossils of *Homo sapiens* have been found in Africa, dating back to around 300,000 years ago.

* These early *Homo sapiens* fossils share many characteristics with modern humans, but also exhibit some differences, suggesting a gradual evolution.

* As you move further away from Africa, the age of *Homo sapiens* fossils generally decreases, indicating a pattern of migration outwards.

* Genetic Evidence:

* Genetic studies have revealed that modern humans have the greatest genetic diversity in Africa.

* The genetic diversity of populations outside Africa decreases with distance from the continent.

* This pattern is consistent with the idea of a single origin in Africa and subsequent migrations.

* Analysis of mitochondrial DNA (passed down maternally) and Y-chromosome DNA (passed down paternally) also strongly supports an African origin for modern humans.

These lines of evidence, when taken together, provide a compelling case for the Out-of-Africa model of human evolution. This model suggests that modern humans evolved in Africa and then migrated out of the continent, eventually replacing other hominin species around the world.

Important Note: There are some ongoing debates within the scientific community regarding the details of human evolution and migration. However, the overwhelming majority of evidence supports the idea of an African origin for modern humans.