What is the 'Out of Africa' theory?

The story of human migration is fascinating. Since humans had not learned to write then, modern scientists have had to rely on archaeological remains to figure out how and when humans moved around the earth. 

Because there is limited evidence from so long ago, the story of early human migrations is constantly updated as new discoveries appear. 

As a result different theories explain how humans spread. 

One of the most important theories in this area is the Out of Africa theory. 

A widely accepted model explains that all humans came from Africa and then moved out of the continent over time. 

In this article, we will explore the evidence for this theory and discuss some of its effects on how we understand human history.

According to evolution humans evolved like other animal species on earth. 

Just as different types of dogs developed over thousands of years but are still part of the 'dog family', which is known in Latin as canis, several kinds of humans lived at different times but are all part of the 'human family', which is known in Latin as homo. 

Modern humans are the last surviving member of the human family. Specifically, we are known by the scientific name homo sapiens. 

However, before we appeared, early versions of humans such as homo habilis, homo neanderthalensis, and others were the first to develop. 

The first humans evolved from other primates which include monkeys and apes between 4 and 2 million years ago somewhere in eastern and southern Africa. 

At that point in history, Africa had many forests so primates thrived among the trees and plentiful food.

The earliest known member of this genus was homo habilis a relatively primitive species but it was the first human to have some new traits. 

First of all, they developed the ability to walk on two legs rather than on all fours. 

Also homo habilis was the first species in our genus to use stone tools. This advance let them make the most of their environment and led to more of them. 

Next, around 1 million years ago, another early human known as homo erectus began to move north out of Africa and into the Middle East. 

Evidence shows that they had the same skills as homo habilis and they also learnt how to start fires when needed.

The Out of Africa theory is the most widely accepted explanation for where modern humans come from and says that all humans came from Africa and then moved out of the continent over time. 

A wide range of evidence supports this model, including genetic studies, fossil records, and archaeological finds. 

Firstly, genetic studies have shown that all modern humans share a common African ancestor dating to about 200,000 years ago. 

Secondly, fossil records show that early human fossils are found only in Africa until about 100,000 years ago. 

After this point, we see the first evidence for human populations outside Africa.

Scientists think humans left Africa for several reasons. 

One idea is that as the African climate became drier humans had to move to find more favourable conditions. 

There is evidence of environmental change in Africa around 100,000 years ago. 

There was less rainfall at the time so early humans had to look for new places to live when forests and trees disappeared. 

Another idea is that humans simply explored their surroundings and eventually left Africa to find new lands to settle. 

Supporters of this idea point to human curiosity and the drive to discover new areas. 

Perhaps early humans felt drawn to travel farther from their homelands which led their populations to grow steadily. 

At that time, modern Homo sapiens began to migrate out of Africa.

The first humans to leave Africa migrated north into the Middle East and from there they continued into Europe and Asia. 

The first modern humans reached Australia around 50,000 years ago, likely by island-hopping across the Indonesian archipelago. 

About 40,000 years ago, they reached Europe, where they clashed with the last Neanderthal humans. 

Since Neanderthals vanished from the record soon after, experts think modern humans either wiped them out or outcompeted them for resources. 

The Americas were the last habitable continents to be settled by early humans, with people reaching South America around 15,000 years ago. 

Experts think humans crossed a frozen 'land bridge' linking eastern Asia to North America during the last major ice age.

Other ideas have been proposed besides the Out of Africa theory. 

One alternative theory is the multiregional hypothesis, a theory that describes how global human populations evolved independently from a common ancestor. 

Some fossil evidence supports this idea but most scientists prefer the Out of Africa theory.

The Out of Africa theory affects our view of human history in several ways. 

First, it suggests that all humans are descended from an ancestor from Africa who lived around 200,000 years ago. 

The shared African origin of all humans means we have a common heritage. 

Second, the theory shows that human migration out of Africa happened slowly over thousands of years. 

In contrast, other ideas suggest there was a single mass exodus from Africa. 

Finally, the theory shows that small genetic differences built up as people moved around the world. 

The fact that all humans share a common ancestor means we are all genetically related and this explains why populations around the world share so much genetic similarity.