Why do scientists think that human population started in africa? and dont post if you got a simple answer..

They tell because of DNA but i cant find anything els like what foundings of DNA and/or what tests, because i think it's bullshit, if we all realy come from africa then why are other ethnicity's weaker if we talk about body health in general, because if that theory is true and we traveled all around the world then every other ethnicity would be much stronger then african's like intelligence developed, and like we all are developing stronger right now(incl black people ofc), you can even tell that white people are becoming little by little a lil bit tan etc whit all the other ethnicity's + black people ll never be white even if they ll live in russia for a 1000's year's, and there is alot more but i am tired as a Sloth.. but what do you think? or do you got any answer or answer's to this?

Only highly intelligent people are aloud to answer, don't make a fool of yourself.
Thank you very much.

Your inability to comprehend the wealth of evidence available and your strange and unsupported concepts about how evolution works do not make the facts any less true.

1. The earliest known human fossils leading right back to ancestral apes are all in Africa.

2. Comparative DNA studies of indiginous populations around the World show that the various strands of early humans all orginate from Africa. In fact the latest data shows more than one migration from Africa and at least one migration back to Africa.

3. You have an odd idea about how evolution works. Strength is but one factor in survival - and it has never been the most important in humans. With human evolution it's brain capacity, intelligence and memory that count. From that viewpoint you're still bashing bones with sticks in Olduvai Gorge

Africans have pure homo sapien blood. Europeans and Asians have 3% neanderthal 97% homo sapien blood. That supports the idea that Europeans and Asians migrated out of Africa.