The planet Earth forms and life begins

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Then human migration

When humans first ventured out of Africa some 60,000 years ago, 
they left genetic footprints still visible today. By mapping the 
appearance and frequency of genetic markers in modern peoples, 
we create a picture of when and where ancient humans moved around 
the world. These great migrations eventually led the descendants 
of a small group of Africans to occupy even the farthest reaches 
of the Earth.

Our species is an African one: Africa is where we first evolved, 
and where we have spent the majority of our time on Earth. 
The earliest fossils of recognizably modern Homo sapiens appear 
in the fossil record at Omo Kibish in Ethiopia, around 200,000 
years ago. Although earlier fossils may be found over the 
coming years, this is our best understanding of when and 
approximately where we originated.

According to the genetic and paleontological record, we only started 
to leave Africa between 60,000 and 70,000 years ago. What set this 
in motion is uncertain, but we think it has something to do with 
major climatic shifts that were happening around that time 
a sudden cooling in the Earth’s climate driven by the onset of 
one of the worst parts of the last Ice Age. This cold snap would have 
made life difficult for our African ancestors, and the genetic evidence 
points to a sharp reduction in population size around this time. 
In fact, the human population likely dropped to fewer than 10,000. 
We were holding on by a thread.

Once the climate started to improve, after 70,000 years ago, 
we came back from this near-extinction event. The population expanded, 
and some intrepid explorers ventured beyond Africa. The earliest people 
to colonize the Eurasian landmass likely did so across the Bab-al-Mandab 
Strait separating present-day Yemen from Djibouti. These early 
beachcombers expanded rapidly along the coast to India, and reached 
Southeast Asia and Australia by 50,000 years ago. 
The first great foray of our species beyond Africa had led us 
all the way across the globe.

Slightly later, a little after 50,000 years ago, a second group appears 
to have set out on an inland trek, leaving behind the certainties of 
life in the tropics to head out into the Middle East and southern 
Central Asia. From these base camps, they were poised to colonize 
the northern latitudes of Asia, Europe, and beyond.

Around 20,000 years ago a small group of these Asian hunters headed into 
the face of the storm, entering the East Asian Arctic during the 
Last Glacial Maximum. At this time the great ice sheets covering 
the far north had literally sucked up much of the Earth’s moisture 
in their vast expanses of white wasteland, dropping sea levels by more 
than 300 feet. This exposed a land bridge that connected the Old World 
to the New, joining Asia to the Americas. In crossing it, the hunters 
had made the final great leap of the human journey. 
By 15,000 years ago they had penetrated the land south of the ice, 
and within 1,000 years they had made it all the way to the tip of 
South America. Some may have even made the journey by sea.

The story doesn’t end there, of course. The rise of agriculture around 
10,000 years ago—and the population explosion it created—has left 
a dramatic impact on the human gene pool. The rise of empires, the 
astounding oceangoing voyages of the Polynesians, even the 
extraordinary increase in global migration over the past 500 years 
could all leave traces in our DNA. There are many human journey 
questions waiting to be asked and answered.

some world population information

world statistics

men work statistics

Over time our brains ?

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