अग्रतश्चतुरो वेदाः पृष्ठतः सशरं धनुः।
इदं ब्राह्ममिदं क्षात्रं शापादपि शरादपि॥

-- self explanatory

 
 

The difference between you and me is that I am a Homo Sapien and you are just a homo.

- A retort to a friend lol

 
 

Be prepared for any and and all disappointments.
- me

 
 

The OOA theory relatively recently in evolutionary history modern humans started migrating from Africa and over the course of time differentiated into the various races that we know today. As far as I know it doesn't explain why those humans started migrating only then and not before or after.

In that regard i want to advance a hypothesis that humans migrate to other parts of the world only when the climatic conditions to migrate there become conducive. Therefore, the temperatures in Africa might have increased or decreased at that time which led to those early humans migrating from there.
Such a migration is happening right now where people from different regions of the world are able to migrate to other regions. They can do so because the climatic conditions that previously posed as a barrier have now been overcome because of better food(such as to overcome vitamin D deficiency ) and protective equipment available(such as sunscreen, winter jackets and boots).

There might come a time in future when once again the earth starts cooling off and the ice sheets start expanding from the polar regions towards the equator at such a time the human migration will once again reduce or stop because under such circumstances migration will once more be unfeasible.

 
 

If you want to live longer move fast. If you want to live forever move at the speed of light.
--- on  the effects of time dilation